chiefmark

I have a 2000 vette that has over heated in two different parades, and the cooling fans were not running. I'm know I have a sensor problem because the gauge says its running at 165 degrees and a inferred temp said it was 195 degrees. the fans can be turned on with a computer but will not come on by turning the AC on, please help!

dougbfresh

What does the OP think overheating is?

dougbfresh

You would be wrong.

dougbfresh

How about the people that built it, the 2nd fan doesn't even come on till 225+

Evil-Twin

You have no idea about how this car was designed/// Your thinking on your coolant temp is wrong... Ask me how I know.... before you embarrass yourself further.. take a look at the red line on your temp gauge. You will notice the red line is at the 255 F mark... meaning anything below this line is considererd normal. We designed the cooling fans to work in conjunction with the AC, and the vehicle speed, meaning fans are turned off after reaching a rolling speed commencerate with the designed fan speed.. this is done ( By design) to allow the fans to work over a longer life span without burning out. The fan speeds are programmed into the PCM to command on and off under specific driving condiditions.

This is how we designed the cooling system algorithims:
The low speed cooling fans are turned on when the coolant temperature reaches 108°C (226°F). They are turned off if the coolant temperature lowers to 104°C (219°F). The high speed cooling fans are turned on when the coolant temperature reaches 113°C (235°F). they are turned off if the coolant temperature lowers to 108°C (226°F). When the A/C is on and the coolant temperature reaches 85°C (185°F), the low speed cooling fans will be turned on at vehicle speeds less than 56 kPh (35 mph).
When the fans turn on, it is in no means an indicator of over heating.. Overheating occurs above 255 F. Changing stats and fan turn on points have no bearing on an overheat condidition on the design of the motor. Thre Motor is designed to handle temps in excess of 250 F all day long. You can gain some tuning advantage with cooler temps, but in not way will engine temps at 207F be considered overheating.. BTW changing a stat has no real bearing on how Hot the coolant gets..once opened.. the only thing controlling the coolant temp is the heat transfer rate and flow rate of the radiator.
TYVM
Bill

lucky131969

"America stands for freedom....But if you think you're free...try walkin into a deli.....and urinating on the cheese"

"Anarchy Burger"...by The Vandals..

dougbfresh

The question is WHAT does the OP think is overheating-
Till the pressure cap POPS, you have not OVERHEATED! 220 in heavy traffic on a hot day is NOT overheating.

lucky131969

Come on now. In all fairness, until the OP provides more details, it's hard to provide a complete response.

chiefmark

I don't know what the actual temp was at the time because it was giving me a false reading, but it was boiling coolant out around the cap. the first thing I did was put a new cap on and then replaced the relays for the fans and that was just throwing money away because the relays were good. I have a friend that looked at it and we hook his scanning machine up to it and he could turn the fans on and off. So why will the fans not come on when the AC is on? and the temp sensor control the fans?

SuzukiDan7

Evil Twin you were actually on the Corvette development team? Thats awesome, and being a programming nerd I like to know the logic behind the fans. I have often wondered if the fans waited too long to come on in slow traffic as I watch my temps rise to 220+. I can understand the concern as I also like to see temps always on the low end of the scale. But if its nothing to worry about, then I'll stop worrying

To the OP, it sounds like your temp sensor has gone bad, not sure how to check it though.

SacCityCorvette

Hi Everyone,
If you dont want to wait until your temp gets to high, we have a new product that you might be interested in. Its perfect for parades, traffic and cooling down in the pits. Heres a link you can check out if your interested.
http://forums.corvetteforum.com/nort...-corvette.html

1999_TRC

Seriously? You hijack someone's troubleshooting thread, to plug your product? Really lame.

bobby777

Experts on cooling a motor--help the guy with his fan issue-

SacCityCorvette

1999_TRC
Lets see, chiefmark said his fans are not coming on with the a/c, so it sounds like he was trying to use the a/c to kick the fans on to cool his Vette down during the parade.
So I was offering something that will help keep his Vette running cooler during those times without all the wear and tear and fuel consumption of running the a/c. I don't believe I hijacked his thread by showing him a product that could benefit him during the parades that he likes to participate in. I didn’t show him a transmission or something that did not pertain to his thread.
On another note, being one of the many supporting venders that keeps this awesome forum free for many Corvette owners, I do not think its a bad thing if a supporting vender wants to “plug” their product if it pertains to to the topic and is beneficial.

If I am wrong, I'm sure I will get flamed for it.

BTW, was your comment beneficial to this thread?
Talk about lame!

SacCityCorvette

chiefmark, is your a/c compressor actually kicking on and the fans do not come on? I don't believe the fans will come on if say the a/c system is low on charge and the compressor is not engaging.

chiefmark

Yes the compressor is coming on but the fans just don't come on, I guess it all has to do with the sensor. Thanks to everyone for your help, I will replace the sensor then I might be back if that doesn't work. Mark

lucky131969

Ok. The PCM enables the fans differently for A/C input, and coolant temperature. The PCM will enable the fans to low, when the A/C head pressure is above 219 psi, and enable to high when the pressure is above 225 psi.


A little reading:

Engine Cooling Fan Description - Electric

The electric cooling fan(s) are used to cool engine coolant flowing through the radiator. The fans are also used to cool the refrigerant flowing through the A/C condenser.

The electric cooling fan(s) are controlled by the PCM. The PCM controls the ground path for the three cooling fan relay(s). The relay(s) are used to control the high current flow to power the cooling fan motors. Both fans operate together. When minimum cooling is required, the PCM energizes cooling fan relay #1 and both fans operate at low speed, since the fans are connected is series through cooling fan relay #3. Cooling fan relay #2 and #3 are both OFF. When maximum cooling is required, the PCM energizes all three cooling fan relays. The left fan is still powered through cooling fan relay #1, but is now grounded through cooling fan relay #3. The right fan is now powered directly through cooling fan relay #2 and both fans operated at high speed.

The PCM will also enable the cooling fans after the ignition is turned off. When the engine coolant temperature exceeds 140°C (284°F) and the ignition is turned off, the cooling fans will be enabled on low speed.

Low Speed Cooling Fans
The low speed cooling fans are controlled by the PCM based on the following inputs:

The A/C system
The Engine Coolant Temperature (ECT) sensor
The Vehicle Speed Sensor (VSS).
The PCM will turn the low speed cooling fans ON when any of the following conditions exist at idle:

Certain PCM Diagnostic Trouble Codes (DTCs) are set.
ECT above 104°C (219°F) will enable low speed fans.
A/C head pressure above 219 psi.
Once the low speed fans are turned ON by Engine Coolant Temperature, the PCM will turn the fans OFF when that temperature has dropped about 6°C (11°F). If the low speed cooling fans are turned ON by high A/C head pressure, the PCM will turn the fans OFF when the pressure has dropped to 150 psi. The minimum ON time for the low speed cooling fans is 50 seconds.

When engine speed is above 3500 RPM for 12 seconds and the engine oil temperature is above 127°C (261°F), the low speed cooling fans will be turned ON.

High Speed Cooling Fans
The High Speed Cooling Fans are controlled by the PCM based on the following inputs:

The A/C system
The Engine Coolant Temperature (ECT) sensor
The Vehicle Speed Sensor (VSS).
The PCM will enable high speed cooling for both fans when any of the following conditions exist:

Certain PCM Diagnostic Trouble Codes (DTCs) set.
ECT above 109°C (228°F).
A/C head pressure above 225 psi.
Once the high speed cooling fans are turned ON by the Engine coolant temperature, the PCM will turn the fans OFF when that temperature has dropped about 6°C (11°F). If the high speed cooling fans are turned ON by high A/C head pressure, the PCM will turn the fans OFF when the pressure has dropped to 180 psi. The minimum ON time for the high speed cooling fans is 26 seconds.

chiefmark

Thanks a lot I think this is going to help me!

SacCityCorvette

I'm sure this is probably a dumb question but did you check the fan fuses, the big 30 amp fuses in the fuse /relay box under the hood?
Just checking.

SacCityCorvette

Do the fans ever come on like the normally should without the a/c?
I know of a guy that had one fan motor go bad and he didnt realize it untill the other one went bad. The first one may have not been working for yrs for all he knew. Kind of like when a head light go out, some poeple dont realize until someone tells them or the other light goes out.
Just a thought.