1995 A/C discharge not cold
06-11-2017, 03:29 PM
#1
Burning Brakes
Thread Starter
1995 A/C discharge not cold
Up here in the mountains, today was the first day I needed/wanted A/C. The air discharge is only 52 degrees. Did not cool the cabin well at all.
I checked the 134a Charge with my gauge. On the low side the pressure is between the two arrows for the ambient air temp.
The air velocity (blast) out of the discharge ports is normal.
There is no crud/junk between the radiator and condenser and the front of the condenser is clean.
When I came in to write this post, I started to wonder if the air door is moving fully ??? How can I check this ?
Amy thoughts what may be the problem, giving consideration to what I have already checked above..
Thank You
8Valve
I checked the 134a Charge with my gauge. On the low side the pressure is between the two arrows for the ambient air temp.
The air velocity (blast) out of the discharge ports is normal.
There is no crud/junk between the radiator and condenser and the front of the condenser is clean.
When I came in to write this post, I started to wonder if the air door is moving fully ??? How can I check this ?
Amy thoughts what may be the problem, giving consideration to what I have already checked above..
Thank You
8Valve
06-11-2017, 04:21 PM
#2
Le Mans Master
Manual or auto A/C system? I'm guessing auto C68.
"I checked the 134a Charge with my gauge. On the low side the pressure is between the two arrows for the ambient air temp".
What was the pressure and was it cycling up and down?
(Do you have a standard set of gauges?)
Is the compressor turning, clutch engaged and are the fat pipes (receiver dryer & top pipe into evaporator) cold?
We have to determine first if the compressor is pumping normally, cycling and evaporator is cold before we get into the blend doors. (troubleshooting automatic system much different the manual system).
If it is an auto system, there are several ways to check the door but let's do step 1 first and make sure things under the hood are running normal.
"I checked the 134a Charge with my gauge. On the low side the pressure is between the two arrows for the ambient air temp".
What was the pressure and was it cycling up and down?
(Do you have a standard set of gauges?)
Is the compressor turning, clutch engaged and are the fat pipes (receiver dryer & top pipe into evaporator) cold?
We have to determine first if the compressor is pumping normally, cycling and evaporator is cold before we get into the blend doors. (troubleshooting automatic system much different the manual system).
If it is an auto system, there are several ways to check the door but let's do step 1 first and make sure things under the hood are running normal.
06-11-2017, 06:15 PM
#3
Burning Brakes
Thread Starter
Pcolt94;
Thanks for the response.
The system is 1995 Auto A/C.
I did not write down the pressure. When I saw it was between the two arrows (min/max) at the set ambient temp, thats as far as I went.
I did not notice any fluctuation in the pressure reading, but again I was not looking at it for any period of time. I assume the compressor is running since the outside temp was 92 degrees and I measured with a infrared thermometer the discharge air and saw 52 degrees. Again I did not check the fat pipes for cold. I am new at this A/C trouble shooting.
Tomorrow, I will be in the shop all day. I will check exactly what you asked and make a post with my findings, before lunch time. How much fluctuation in the pressure readings should I be looking for, ie just a tad or some major swings.
My sincere thanks
8Valve
Thanks for the response.
The system is 1995 Auto A/C.
I did not write down the pressure. When I saw it was between the two arrows (min/max) at the set ambient temp, thats as far as I went.
I did not notice any fluctuation in the pressure reading, but again I was not looking at it for any period of time. I assume the compressor is running since the outside temp was 92 degrees and I measured with a infrared thermometer the discharge air and saw 52 degrees. Again I did not check the fat pipes for cold. I am new at this A/C trouble shooting.
Tomorrow, I will be in the shop all day. I will check exactly what you asked and make a post with my findings, before lunch time. How much fluctuation in the pressure readings should I be looking for, ie just a tad or some major swings.
My sincere thanks
8Valve
Manual or auto A/C system? I'm guessing auto C68.
"I checked the 134a Charge with my gauge. On the low side the pressure is between the two arrows for the ambient air temp".
What was the pressure and was it cycling up and down?
(Do you have a standard set of gauges?)
Is the compressor turning, clutch engaged and are the fat pipes (receiver dryer & top pipe into evaporator) cold?
We have to determine first if the compressor is pumping normally, cycling and evaporator is cold before we get into the blend doors. (troubleshooting automatic system much different the manual system).
If it is an auto system, there are several ways to check the door but let's do step 1 first and make sure things under the hood are running normal.
"I checked the 134a Charge with my gauge. On the low side the pressure is between the two arrows for the ambient air temp".
What was the pressure and was it cycling up and down?
(Do you have a standard set of gauges?)
Is the compressor turning, clutch engaged and are the fat pipes (receiver dryer & top pipe into evaporator) cold?
We have to determine first if the compressor is pumping normally, cycling and evaporator is cold before we get into the blend doors. (troubleshooting automatic system much different the manual system).
If it is an auto system, there are several ways to check the door but let's do step 1 first and make sure things under the hood are running normal.
06-11-2017, 09:21 PM
#5
Le Mans Master
Sounds like you don’t have basic gauges but are using one of those gauges on a Freon 134 bottle you get at an auto part store. Right or wrong?
So it sounds like it's part of a recharge kit but I'm not sure.
So if you have 52* air out of the vents and it 90* outside, it seems like the A/C is basically working but still check as you said you were going to.
Assuming you are on the low pressure port and if the compressor is cycling, the gauge should pull down to 22.5 psi as you rev the engine, and then go up to about 46 psi and then the cycling switch closes again and will pull back down to 22.5. Depending on how much gas is in the system and the outside air temperature will determine how often the cycle will repeat.
The blend door is viewable by removing the blower power module in the evaporator case on top in the engine compartment. If you look with a flashlight you can see the door. If you run the temp on the controller (no need to start car just key on) to 60 and check position, then 90 and check position it should change about 90 degrees in rotation.
In addition if the compressor is cycling every 5 or 6 seconds that may too much and indicates low Freon which may make the discharge air in the car not as cool as it should be.
You can see the center of the compressor shaft turning when the clutch engages. The click can also be heard when the clutch engages. Keep your fingers clear of the belt and pulleys.
So it sounds like it's part of a recharge kit but I'm not sure.
So if you have 52* air out of the vents and it 90* outside, it seems like the A/C is basically working but still check as you said you were going to.
Assuming you are on the low pressure port and if the compressor is cycling, the gauge should pull down to 22.5 psi as you rev the engine, and then go up to about 46 psi and then the cycling switch closes again and will pull back down to 22.5. Depending on how much gas is in the system and the outside air temperature will determine how often the cycle will repeat.
The blend door is viewable by removing the blower power module in the evaporator case on top in the engine compartment. If you look with a flashlight you can see the door. If you run the temp on the controller (no need to start car just key on) to 60 and check position, then 90 and check position it should change about 90 degrees in rotation.
In addition if the compressor is cycling every 5 or 6 seconds that may too much and indicates low Freon which may make the discharge air in the car not as cool as it should be.
You can see the center of the compressor shaft turning when the clutch engages. The click can also be heard when the clutch engages. Keep your fingers clear of the belt and pulleys.
06-11-2017, 09:31 PM
#6
Burning Brakes
Thread Starter
Bill, I was thinking along the sale lines. I do have a recharge kit, with what appears to be a quality gauge/hose assembly. The gauge has a rotating face with a arrow to point to the ambient temp and it also has 2 other lines that are the min/max charge. My gauge shows my charge is 7/8 on the scale from being max charge. I am hesitant to charge above the max line, I dont want to do damage.
8Valve
8Valve
06-11-2017, 10:55 PM
#7
Burning Brakes
Thread Starter
Pcolt;
Thanks for the update.
I will check everything for suggested now and earlier tomorrow. It will now be probably after lunch, but it will be done. I will post my findings. You are correct, no basic gauges, just a NAPA recharge kit
Thank You
8Valve
Thanks for the update.
I will check everything for suggested now and earlier tomorrow. It will now be probably after lunch, but it will be done. I will post my findings. You are correct, no basic gauges, just a NAPA recharge kit
Thank You
8Valve
Sounds like you don’t have basic gauges but are using one of those gauges on a Freon 134 bottle you get at an auto part store. Right or wrong?
So it sounds like it's part of a recharge kit but I'm not sure.
So if you have 52* air out of the vents and it 90* outside, it seems like the A/C is basically working but still check as you said you were going to.
Assuming you are on the low pressure port and if the compressor is cycling, the gauge should pull down to 22.5 psi as you rev the engine, and then go up to about 46 psi and then the cycling switch closes again and will pull back down to 22.5. Depending on how much gas is in the system and the outside air temperature will determine how often the cycle will repeat.
The blend door is viewable by removing the blower power module in the evaporator case on top in the engine compartment. If you look with a flashlight you can see the door. If you run the temp on the controller (no need to start car just key on) to 60 and check position, then 90 and check position it should change about 90 degrees in rotation.
In addition if the compressor is cycling every 5 or 6 seconds that may too much and indicates low Freon which may make the discharge air in the car not as cool as it should be.
You can see the center of the compressor shaft turning when the clutch engages. The click can also be heard when the clutch engages. Keep your fingers clear of the belt and pulleys.
So it sounds like it's part of a recharge kit but I'm not sure.
So if you have 52* air out of the vents and it 90* outside, it seems like the A/C is basically working but still check as you said you were going to.
Assuming you are on the low pressure port and if the compressor is cycling, the gauge should pull down to 22.5 psi as you rev the engine, and then go up to about 46 psi and then the cycling switch closes again and will pull back down to 22.5. Depending on how much gas is in the system and the outside air temperature will determine how often the cycle will repeat.
The blend door is viewable by removing the blower power module in the evaporator case on top in the engine compartment. If you look with a flashlight you can see the door. If you run the temp on the controller (no need to start car just key on) to 60 and check position, then 90 and check position it should change about 90 degrees in rotation.
In addition if the compressor is cycling every 5 or 6 seconds that may too much and indicates low Freon which may make the discharge air in the car not as cool as it should be.
You can see the center of the compressor shaft turning when the clutch engages. The click can also be heard when the clutch engages. Keep your fingers clear of the belt and pulleys.
Last edited by 8valve; 06-11-2017 at 10:58 PM.
06-12-2017, 09:42 AM
#8
Drifting
Last edited by RIC96; 06-12-2017 at 09:45 AM.
06-12-2017, 11:52 AM
#9
Burning Brakes
Thread Starter
Pcolt;
Here are the findings on the AC test this morning.
1. No Codes (fan up/down for 6 sec, then auto) no codes shown
2. Pulled fan power module. Engine off, heat and air control does fully move the
door
3. Compressor turning, clutch engages properly
4. Low Pressure pipes and top of dryer are quite cold. Cant get a real temp measurement with my infrared gun due to engine heat messing up the reading
5. Shop ambient temperature 74 degrees
6. No real gauge set, but recharge kit gauge shows 45 psi when engine/AC turned
on. It does pull down to roughly 25 psi on cycle. After 30 minutes of running
the charge shows 50 psi.
7. Per my 1995 owners manual to reset the A/C controller, pull the radio and courtesy fuses for 1 min. I left out for 5 minutes.
8. Re-started car, in a few minutes, my center discharge was 39 degrees, left discharge 43 degrees and right discharge 40 degrees. All in Recirc mode
9. In bi-level mode center 44 degrees, right 43 degrees and left 43 degrees.
10. WATCH THIS….. Plus 20 minutes of running, in Recirc mode, Center 52 degrees,
right 53 and left 55 degrees. Back to the original problem after running a
while, 52 degree air discharge.
Is it possible that the Gauge on the re-charge kit is inaccurate and I am really low on charge ???
I live very remote in the mountains. The nearest A/C shop is 75 miles one way, I would really like to fix this issue, save the 150 miles and huge bucks.
Thanks for any thoughts.
8Valve
Here are the findings on the AC test this morning.
1. No Codes (fan up/down for 6 sec, then auto) no codes shown
2. Pulled fan power module. Engine off, heat and air control does fully move the
door
3. Compressor turning, clutch engages properly
4. Low Pressure pipes and top of dryer are quite cold. Cant get a real temp measurement with my infrared gun due to engine heat messing up the reading
5. Shop ambient temperature 74 degrees
6. No real gauge set, but recharge kit gauge shows 45 psi when engine/AC turned
on. It does pull down to roughly 25 psi on cycle. After 30 minutes of running
the charge shows 50 psi.
7. Per my 1995 owners manual to reset the A/C controller, pull the radio and courtesy fuses for 1 min. I left out for 5 minutes.
8. Re-started car, in a few minutes, my center discharge was 39 degrees, left discharge 43 degrees and right discharge 40 degrees. All in Recirc mode
9. In bi-level mode center 44 degrees, right 43 degrees and left 43 degrees.
10. WATCH THIS….. Plus 20 minutes of running, in Recirc mode, Center 52 degrees,
right 53 and left 55 degrees. Back to the original problem after running a
while, 52 degree air discharge.
Is it possible that the Gauge on the re-charge kit is inaccurate and I am really low on charge ???
I live very remote in the mountains. The nearest A/C shop is 75 miles one way, I would really like to fix this issue, save the 150 miles and huge bucks.
Thanks for any thoughts.
8Valve
Sounds like you don’t have basic gauges but are using one of those gauges on a Freon 134 bottle you get at an auto part store. Right or wrong?
So it sounds like it's part of a recharge kit but I'm not sure.
So if you have 52* air out of the vents and it 90* outside, it seems like the A/C is basically working but still check as you said you were going to.
Assuming you are on the low pressure port and if the compressor is cycling, the gauge should pull down to 22.5 psi as you rev the engine, and then go up to about 46 psi and then the cycling switch closes again and will pull back down to 22.5. Depending on how much gas is in the system and the outside air temperature will determine how often the cycle will repeat.
The blend door is viewable by removing the blower power module in the evaporator case on top in the engine compartment. If you look with a flashlight you can see the door. If you run the temp on the controller (no need to start car just key on) to 60 and check position, then 90 and check position it should change about 90 degrees in rotation.
In addition if the compressor is cycling every 5 or 6 seconds that may too much and indicates low Freon which may make the discharge air in the car not as cool as it should be.
You can see the center of the compressor shaft turning when the clutch engages. The click can also be heard when the clutch engages. Keep your fingers clear of the belt and pulleys.
So it sounds like it's part of a recharge kit but I'm not sure.
So if you have 52* air out of the vents and it 90* outside, it seems like the A/C is basically working but still check as you said you were going to.
Assuming you are on the low pressure port and if the compressor is cycling, the gauge should pull down to 22.5 psi as you rev the engine, and then go up to about 46 psi and then the cycling switch closes again and will pull back down to 22.5. Depending on how much gas is in the system and the outside air temperature will determine how often the cycle will repeat.
The blend door is viewable by removing the blower power module in the evaporator case on top in the engine compartment. If you look with a flashlight you can see the door. If you run the temp on the controller (no need to start car just key on) to 60 and check position, then 90 and check position it should change about 90 degrees in rotation.
In addition if the compressor is cycling every 5 or 6 seconds that may too much and indicates low Freon which may make the discharge air in the car not as cool as it should be.
You can see the center of the compressor shaft turning when the clutch engages. The click can also be heard when the clutch engages. Keep your fingers clear of the belt and pulleys.
06-12-2017, 02:19 PM
#10
Burning Brakes
Thread Starter
Ric;
Thanks for your thoughts. However, I have owned this 1995 for 5 years. In the past, I could freeze you. In the past, in good weather,
I could leave the car in total sun while in church for most of the day. Come out, open the windows, A/C on Max, hit the interstate, A/c Working, windows open to evac the heat and before the first exit (8 miles), windows were shut and the car was cold inside. No, I have a problem.
I just went out after lunch. Car sitting in my shop, no sun, 85 degrees. In a few minutes I had 39 degree out of the ducts. In 15 minutes, the air coming out of the ducts was at 53 degrees, up from 39 degrees.
8Valve-
Thanks for your thoughts. However, I have owned this 1995 for 5 years. In the past, I could freeze you. In the past, in good weather,
I could leave the car in total sun while in church for most of the day. Come out, open the windows, A/C on Max, hit the interstate, A/c Working, windows open to evac the heat and before the first exit (8 miles), windows were shut and the car was cold inside. No, I have a problem.
I just went out after lunch. Car sitting in my shop, no sun, 85 degrees. In a few minutes I had 39 degree out of the ducts. In 15 minutes, the air coming out of the ducts was at 53 degrees, up from 39 degrees.
8Valve-
Based on my experience, a hot interior is just the nature of the beast. I used live in Texas and if I parked in the sun on a 95 degree day, it was hard for the AC to cool the car when I returned. On a 95 degree night, which is not uncommon, the air worked just fine. Too much glass coupled with a dark interior equals microwave!
06-12-2017, 03:29 PM
#12
Drifting
Ric;
Thanks for your thoughts. However, I have owned this 1995 for 5 years. In the past, I could freeze you. In the past, in good weather,
I could leave the car in total sun while in church for most of the day. Come out, open the windows, A/C on Max, hit the interstate, A/c Working, windows open to evac the heat and before the first exit (8 miles), windows were shut and the car was cold inside. No, I have a problem.
I just went out after lunch. Car sitting in my shop, no sun, 85 degrees. In a few minutes I had 39 degree out of the ducts. In 15 minutes, the air coming out of the ducts was at 53 degrees, up from 39 degrees.
8Valve-
Thanks for your thoughts. However, I have owned this 1995 for 5 years. In the past, I could freeze you. In the past, in good weather,
I could leave the car in total sun while in church for most of the day. Come out, open the windows, A/C on Max, hit the interstate, A/c Working, windows open to evac the heat and before the first exit (8 miles), windows were shut and the car was cold inside. No, I have a problem.
I just went out after lunch. Car sitting in my shop, no sun, 85 degrees. In a few minutes I had 39 degree out of the ducts. In 15 minutes, the air coming out of the ducts was at 53 degrees, up from 39 degrees.
8Valve-
06-12-2017, 04:16 PM
#13
Le Mans Master
Ric;
Thanks for your thoughts. However, I have owned this 1995 for 5 years. In the past, I could freeze you. In the past, in good weather,
I could leave the car in total sun while in church for most of the day. Come out, open the windows, A/C on Max, hit the interstate, A/c Working, windows open to evac the heat and before the first exit (8 miles), windows were shut and the car was cold inside. No, I have a problem.
I just went out after lunch. Car sitting in my shop, no sun, 85 degrees. In a few minutes I had 39 degree out of the ducts. In 15 minutes, the air coming out of the ducts was at 53 degrees, up from 39 degrees.
8Valve-
Thanks for your thoughts. However, I have owned this 1995 for 5 years. In the past, I could freeze you. In the past, in good weather,
I could leave the car in total sun while in church for most of the day. Come out, open the windows, A/C on Max, hit the interstate, A/c Working, windows open to evac the heat and before the first exit (8 miles), windows were shut and the car was cold inside. No, I have a problem.
I just went out after lunch. Car sitting in my shop, no sun, 85 degrees. In a few minutes I had 39 degree out of the ducts. In 15 minutes, the air coming out of the ducts was at 53 degrees, up from 39 degrees.
8Valve-
I will say that is a strange problem not that I have heard yet.
Get IR temp reading on the top pipe coming out of the evaporator when it's good and bad. Don’t know how valid the results would be but might give another data point.
Other than the control head giving a code, it is also a diagnostic tool than can tell you positions and temperatures of all kinds of things. This is in the FSM as well as info on the internet although a lot of info has disappeared for the C4 over the years. It can tell you the position of the blend door when the problem is happening. If by chance the door is moving from its max open full cold position and goes toward warm, you can see that.
Check out operation of control head
http://web.archive.org/web/200402031...=193&TopicID=2
The parameter #12 is for the door position. The cold position is -155 and should always stay there as long as the temperature control is not changed from 60* It is more difficult to learn how to us this than actually use it after learned.
Last edited by pcolt94; 06-12-2017 at 04:16 PM.
06-12-2017, 04:46 PM
#14
Melting Slicks
Heater core should always have flow.
Considering the time it is taking for the temp output to rise, i'd think pcolt94's suggestion to check the blend door position would be the prudent next step.
Sounds like some heated air is mixing in with the cool air. At startup the cold heater core has no effect, but once it warms up it becomes a problem.
Considering the time it is taking for the temp output to rise, i'd think pcolt94's suggestion to check the blend door position would be the prudent next step.
Sounds like some heated air is mixing in with the cool air. At startup the cold heater core has no effect, but once it warms up it becomes a problem.
06-12-2017, 06:15 PM
#15
Burning Brakes
Thread Starter
I will answer Pcolt, BeLairBrian and Jim Lentz in one post. Being remote in the Mts, I only have dial up internet at 24.4K (best speed)..don't laugh ha ha.
Jim, I have not run heat since last fall. I went out after dinner, the hot air blast from the heater is enough to melt steel. Great Flow.
Belairbrian, Yes, I believe its also in the Blend door. Your right, on a cold start the A/C is blasting cold air before the engine gets to temp for the T Stat to open, at temperature, a blend door that opened a tad would sure heat the A/C discharge
PColt, trying to get a IR reading on the dryer is not possible. To much engine heat and blast from both cooling fans heat up the dryer and Low Pressure pipes so I get false readings. For example, when I get 39 degree discharge output, I can take a IR reading on the dryer and I read varying but around 60. That temp is not possible when the discharge temp is 39. Its false due to all the engine heat keeping the outside of the dryer and pipes warm.
I will read the link you supplied as well a dive into the FSM tonight. Two questions;
1. I read on the web that a faulty A/C compressor clutch cycle switch can either cause no cold air or discharge that is not cold as it should be. Is it possible that this switch when it gets heated by engine heat may start to fail, and is not cycling properly. Can this switch be jumped to prove a good or bad switch
2. In the morning I will remove the 4 screws holding in the blower speed module so as soon as I see a increase in temp from 39, I can pull the module and see if the blend door as opened some. From visually watching the door going from cool to heat, the door appears to move properly. I also want to make a wire hook to reach in and see if the door might be loose so it could move on its own. Or its getting a errant signal from the controller to open some, just enough to blend heat/cold and give the 52 degree (varies a few degrees) discharge.
3. Ok, 3 questions ha ha. For a test is there any way to disable the blend door when its in the cool position so nothing can move it. I sure don't need heat now, but this could quickly prove a blend door. Or maybe I can wedge something in the door swing area so it cant open ?
Thanks guys for all your support. I will prevail, but I sure don't know when LOL!
8Valve
Jim, I have not run heat since last fall. I went out after dinner, the hot air blast from the heater is enough to melt steel. Great Flow.
Belairbrian, Yes, I believe its also in the Blend door. Your right, on a cold start the A/C is blasting cold air before the engine gets to temp for the T Stat to open, at temperature, a blend door that opened a tad would sure heat the A/C discharge
PColt, trying to get a IR reading on the dryer is not possible. To much engine heat and blast from both cooling fans heat up the dryer and Low Pressure pipes so I get false readings. For example, when I get 39 degree discharge output, I can take a IR reading on the dryer and I read varying but around 60. That temp is not possible when the discharge temp is 39. Its false due to all the engine heat keeping the outside of the dryer and pipes warm.
I will read the link you supplied as well a dive into the FSM tonight. Two questions;
1. I read on the web that a faulty A/C compressor clutch cycle switch can either cause no cold air or discharge that is not cold as it should be. Is it possible that this switch when it gets heated by engine heat may start to fail, and is not cycling properly. Can this switch be jumped to prove a good or bad switch
2. In the morning I will remove the 4 screws holding in the blower speed module so as soon as I see a increase in temp from 39, I can pull the module and see if the blend door as opened some. From visually watching the door going from cool to heat, the door appears to move properly. I also want to make a wire hook to reach in and see if the door might be loose so it could move on its own. Or its getting a errant signal from the controller to open some, just enough to blend heat/cold and give the 52 degree (varies a few degrees) discharge.
3. Ok, 3 questions ha ha. For a test is there any way to disable the blend door when its in the cool position so nothing can move it. I sure don't need heat now, but this could quickly prove a blend door. Or maybe I can wedge something in the door swing area so it cant open ?
Thanks guys for all your support. I will prevail, but I sure don't know when LOL!
8Valve
I'd say take a drive and do the same test to get some air over the condenser which affects how the system works but you have already done that.
I will say that is a strange problem not that I have heard yet.
Get IR temp reading on the top pipe coming out of the evaporator when it's good and bad. Don’t know how valid the results would be but might give another data point.
Other than the control head giving a code, it is also a diagnostic tool than can tell you positions and temperatures of all kinds of things. This is in the FSM as well as info on the internet although a lot of info has disappeared for the C4 over the years. It can tell you the position of the blend door when the problem is happening. If by chance the door is moving from its max open full cold position and goes toward warm, you can see that.
Check out operation of control head
http://web.archive.org/web/200402031...=193&TopicID=2
The parameter #12 is for the door position. The cold position is -155 and should always stay there as long as the temperature control is not changed from 60* It is more difficult to learn how to us this than actually use it after learned.
I will say that is a strange problem not that I have heard yet.
Get IR temp reading on the top pipe coming out of the evaporator when it's good and bad. Don’t know how valid the results would be but might give another data point.
Other than the control head giving a code, it is also a diagnostic tool than can tell you positions and temperatures of all kinds of things. This is in the FSM as well as info on the internet although a lot of info has disappeared for the C4 over the years. It can tell you the position of the blend door when the problem is happening. If by chance the door is moving from its max open full cold position and goes toward warm, you can see that.
Check out operation of control head
http://web.archive.org/web/200402031...=193&TopicID=2
The parameter #12 is for the door position. The cold position is -155 and should always stay there as long as the temperature control is not changed from 60* It is more difficult to learn how to us this than actually use it after learned.
06-12-2017, 06:39 PM
#16
Melting Slicks
IIRC the blend door motor is on the bottom of the air box under the dash. So access is pretty easy. It was moved from the top in 94 i believe. Should be able to remove and move the blend door. Also that should give you an idea if there is something blocking it.
if you put the HVAC panel in diagnostic mode you can test the door and read the position value.
later c4s don't have a heater valve. Coolant flows through the core any time the engine is running.
if you put the HVAC panel in diagnostic mode you can test the door and read the position value.
later c4s don't have a heater valve. Coolant flows through the core any time the engine is running.
Last edited by belairbrian; 06-12-2017 at 06:41 PM.
06-12-2017, 10:33 PM
#17
Burning Brakes
Thread Starter
Thanks for that info. I cant get back on the vette till later in the day tomorrow. I will post what I find
8Valve
8Valve
IIRC the blend door motor is on the bottom of the air box under the dash. So access is pretty easy. It was moved from the top in 94 i believe. Should be able to remove and move the blend door. Also that should give you an idea if there is something blocking it.
if you put the HVAC panel in diagnostic mode you can test the door and read the position value.
later c4s don't have a heater valve. Coolant flows through the core any time the engine is running.
if you put the HVAC panel in diagnostic mode you can test the door and read the position value.
later c4s don't have a heater valve. Coolant flows through the core any time the engine is running.
06-12-2017, 10:47 PM
#18
Le Mans Master
Don’t try to jam the blend door, bad idea.
You can disconnect the small connector to the motor but if I remember the motor has to be removed first to get to the connector. Remove the motor (2- 7mm screws). But once the motor is removed you can't leave it off because the door will swing freely so it has to be on. It's a keyed shaft goes on one way.
I don’t know what the side effects might have on the operation as the programmer might not like to have the motor disconnected. Just mentioning it, I don’t know myself. If it does not help though I would reconnect it.
I also think the under panel has to be removed to get to the motor and see it.
I will try to post the diagnostic information, easy to read, but need to scan it and make a jpg of it.
You have a strange problem so here is a strange thought. If the compressor was cycling to much that might indicate low Freon. Or if the compressor never cycles due to the cycling switch not opening up, the evaporator can ice up, reduce air flow and might cause a higher output air temperature. Just thinking.
You can disconnect the small connector to the motor but if I remember the motor has to be removed first to get to the connector. Remove the motor (2- 7mm screws). But once the motor is removed you can't leave it off because the door will swing freely so it has to be on. It's a keyed shaft goes on one way.
I don’t know what the side effects might have on the operation as the programmer might not like to have the motor disconnected. Just mentioning it, I don’t know myself. If it does not help though I would reconnect it.
I also think the under panel has to be removed to get to the motor and see it.
I will try to post the diagnostic information, easy to read, but need to scan it and make a jpg of it.
You have a strange problem so here is a strange thought. If the compressor was cycling to much that might indicate low Freon. Or if the compressor never cycles due to the cycling switch not opening up, the evaporator can ice up, reduce air flow and might cause a higher output air temperature. Just thinking.
06-13-2017, 09:07 PM
#19
Burning Brakes
Thread Starter
I did not have a lot of free time for the Vette A/C today. I was able to completely go thru the diagnostics in the FSM using the control head, and each diagnostic returned the positive expected result as given n the FSM.
I am convinced that the blend door is working as designed. The full heat/cold open/closed numbers of the door are exact with the FSM. I have a long probe that you can pick up objects dropped into tight spaces. Removing the Fan speed module I was able to reach in and grab the blend door. Its rigidly mounted on the pivots and the control arm. No way its moving except under command.
Its iffy if I can squeeze time on Wednesday to do further tests, it will most likely be thursday, the problem is very elusive, but the answer is there to be found……I will keep all posted
8Valve
I am convinced that the blend door is working as designed. The full heat/cold open/closed numbers of the door are exact with the FSM. I have a long probe that you can pick up objects dropped into tight spaces. Removing the Fan speed module I was able to reach in and grab the blend door. Its rigidly mounted on the pivots and the control arm. No way its moving except under command.
Its iffy if I can squeeze time on Wednesday to do further tests, it will most likely be thursday, the problem is very elusive, but the answer is there to be found……I will keep all posted
8Valve
Don’t try to jam the blend door, bad idea.
You can disconnect the small connector to the motor but if I remember the motor has to be removed first to get to the connector. Remove the motor (2- 7mm screws). But once the motor is removed you can't leave it off because the door will swing freely so it has to be on. It's a keyed shaft goes on one way.
I don’t know what the side effects might have on the operation as the programmer might not like to have the motor disconnected. Just mentioning it, I don’t know myself. If it does not help though I would reconnect it.
I also think the under panel has to be removed to get to the motor and see it.
I will try to post the diagnostic information, easy to read, but need to scan it and make a jpg of it.
You have a strange problem so here is a strange thought. If the compressor was cycling to much that might indicate low Freon. Or if the compressor never cycles due to the cycling switch not opening up, the evaporator can ice up, reduce air flow and might cause a higher output air temperature. Just thinking.
You can disconnect the small connector to the motor but if I remember the motor has to be removed first to get to the connector. Remove the motor (2- 7mm screws). But once the motor is removed you can't leave it off because the door will swing freely so it has to be on. It's a keyed shaft goes on one way.
I don’t know what the side effects might have on the operation as the programmer might not like to have the motor disconnected. Just mentioning it, I don’t know myself. If it does not help though I would reconnect it.
I also think the under panel has to be removed to get to the motor and see it.
I will try to post the diagnostic information, easy to read, but need to scan it and make a jpg of it.
You have a strange problem so here is a strange thought. If the compressor was cycling to much that might indicate low Freon. Or if the compressor never cycles due to the cycling switch not opening up, the evaporator can ice up, reduce air flow and might cause a higher output air temperature. Just thinking.
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Red 91 (06-19-2017)
06-16-2017, 06:56 PM
#20
Advanced
This sounds like a case of the Ac programmer vaccum system on a 94-96 vaccum liness at the programmer getting soft and weak as the vehicle gets hot. The 94-96 ac programmer vaccum line manifold has rubber tips on them. As the tips age and get hot the tips will collaspe causing blend door to be not be functioning properly. You can take the vaccum lines off and trim the tips off slightly reattach the vaccum lines and see if it works properly. This is not an easy fix as the programmer is in the footwell on the firewall above the drivers feet inside the vehicle. You have to crawl under and look up to remove or repair. Good luck. Gordon Killebrew told me about this problem with the 94-96 models a long time ago.