vetracer

Does anyone know what controls the recirculation door on an electronic A/C system? my 86 blows strong then dies out , then blows strong again. On manually controlled units the recirculation is controlled by switching between "normal" and "max" on the controller. I have the shop manual and have been unable to find this circuit. In the Arizona heat this can be aggravating. Any help would be greatly appreciated. No pics yet of the car in question - but I do have a pic of the matching race version!

nel

According to my Electrical Diagnosis Service manual the recirc door is closed only when the A/C is on (Auto mode) and the temperature is set to 65 degrees. Otherwise, it's open.

The door along with air outlet control doors are moved by different vacuum actuators. They, in turn, are controlled by the Heater and A/C Programmer. The Programmer is an electronic device that also has a vacuum source attached to it. It's located inthe driver's side of the instrument panel (IP), just to the right of the steering column. The valve that moves the recirc. door is on the right hand side of the IP.

Hope this helps. Not sure why your A/C would run strong and then die, though. Doesn't sound like it's the recirc. door, more like a control problem or the blower motor.


[Modified by nel, 5:42 AM 8/9/2002]

PTz-92-LT1

When you say blows strong then dies out...do you mean continuing to cycle between cold then warm and it feels/sounds like there is a pressure build up in the system?

ZylaRace

I think you will find the vent door are controlled by electrically controlled solenoids. The mixer door is electrically controlled. They are all controlled by hte programmer module just above the gas pedal. This is a common failure item. I'm not sure if it is the mixed door circuit or the fan circuit, but the high wattage resistors melt the solder and cause cold solder joints. To fix,reflow the solder. Or just repalce the unit.

Get the head unit to dump the codes and see if the mixer door is full cool or not.

89vette

I think I know what he means. My 89 does the same thing. It blows hard when the recirc door is open. Its louder becasue its sucking air from in the car. Then the door closes and the car is still hot inside and the air hardly comes out of the vents. Then after a few minutes it will open again. There is no way to manually make the door stay open for a more rapid cool. I just chalked it up to the design is 20 years old and that is as good as it gets! The Grand Sport I had would almost blow you over when you put it on high.

aj1988

I am not sure if this is related or not, but I have the problem sometimes where the car will go from A/C to heat. Temp set at 60 and HOT outside. What gives? Also, with fan set on 10 it blows, but doesn't seem to blow very hard at any time.

PTz-92-LT1

Where I am going is this...if you have an electronic A/C unit and your A/C continually cycles from hot to cold the problem is most likely the "Temperature Valve Actuator" or the actual door. To diagnosis this:
1. Start car;
2. Turn A/C on (any mode);
3. Set thermostat to 60 defrees F;
4. Press both up and down fan buttons simultaneously for about 5 seconds until 00 appears;
5. Press down arrow until 34 is displayed;
6. Press AUTO FAN button and note reading "0 to -153¨;
7. Press AUTO FAN button and 34 is now displayed;
8. Press down arrow until 24 is displayed;
9. Press AUTO FAN button and note reading "0 to 153¨;
10. Both readings should be within 10;
11. Repeat steps 2 - 9 above with thermostat set to 90 defrees F.


If the numbers you recorded for 34 and 24 are significantly different (20 or more off), the problem resides with the "Temperature Valve Actuator¨ or the mechanism, which actually touches and moves the door that controls the air mix. This usually manifests itself by giving a code 01 or 02, but in my case it did not, or I just didn't catch it.

If this is the case let me know and I can tell you where to go from there.



[Modified by PTz-92-LT1, 10:26 AM 8/9/2002]

vetracer

No, it is constantly cold, it is just the volume of air. I replaced the blower motor, it works a little better but still blows hard then slows down. I'm certain that the controller or some other part of the system is fluctuating between "normal" mode and "max" or recirculate mode. I just have to figure out what dictates how these modes are selected by the controller and why it seems to have a mind of its own!

PTz-92-LT1

Given the new information I would tend to agree with you. However there it still could be an actuator, a vacuum leak, dirty contacts on the A/C head or a bad A/C programmer. You should first check for error codes, then rule out a vacuum leak, then pull the head out and clean the contacts. If these three things do not offer a remedy, it would most likely leave an actuator valve or A/C programmer.

Frodo

I have the same problem and was wondering how to manually control the door. My 89 blows recirculated air for a few minutes then blows outside air, then back to recirculated. This happens on auto or manual selection. Both are chilled air but the recirc air is colder. I like to blow recirc until the air inside the car is COLD but the A/C controller thinks I ought to have both. LOL Any ideas??

Thanks :flag

dlmeyers

The C68 blower in the auto mode will vary blower speed based on interior temp sensor, outside air temp sensor, and sun load sensor data. All this data is used in an attempt to keep the temp on track. The blower will almost always start out high and gradually drop back (as in less air) as the interior cools (or warms) and will sellect the lowest fan speed to maintain the temp and reduce noise. You can of course, come out of the auto fan mode and go manual. See owners manual. After you first fire up the A/C, push the little fan symbol once and note the number. Do this again after 5 to 10 minutes. Will likely be a lower number unless you are in traffic, 95F, lots of sun. Believe if you push the fan symbol twice, it locks in on the current number. Could be wrong on that, best check the manual.

The temp control door as stated above modulates to maintain the desired temp. The air source door will direct air from either outside or use the air inside the car, depending on the setting. Apparently you must have the temp really low to lock into recirculation mode as noted above. Just for trivia, with the door in "full recirculation" the system will allow 20% outside air to enter. Saw this number last week in the service manual. GM wants you to have some fresh air. Always wondered how so much outside air got in even in "MAX" settings.

If your air is cold and the fan just sounds like it's falling off in the auto mode, could be normal operation unless there is a restriction somewhere.

Stay cool.

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