tjbayless

Just finished converting the A/C system over to 134a. In the process I noticed that the air flow was not coming just the A/C vents, but also coming out of the defrost vents. When I move the temp selector to full hot, the defrost air stops. There have been a couple of times that when I first started the car the air was correct, but after driving for a while the defrost air started blowing again on its own. I have searched through the other threads, but did not find anyone having a similar issue.

86 951 Driver

I'm assuming you have a vacuum leak. What year is your car? You will need to look in the engine bay and see if anything is unplugged or any vacuum lines are broken.

tjbayless

The car is an 85.5. I understood that the air flow control was all operated by electric motor operated valves and that vacuum controlled the heating valve and recirculation. I also noticed that the recirculation doors were closed without the switch being pressed. When I removed the vacuum hose from the left actuator the door opened indicating that I have good vacuum at that point.

Van

It probably has to do with those two sliding arrow controls... you know, those ones I never figured out exactly how they work. And I've had 944s since 1997.

SeaCay

If this is a late dash, there's a vertical slider between the vents in the dash that controls the flow of air to the defrosters. Insure that slider is down, fixed.

tjbayless

Movement of the sliding arrows has no effect. Early in the morning when the car is cold on some days if get full air flow from the center vents. After driving a while suddenly the center vent airflow reduces and air starts coming out of the defroster vents. The defrost slider in the center vents has been in the down position the entire time. Also I rebuilt the center vent doors with new foam seals.

tjbayless

I did a little more testing with the system last night and I am now starting to think that the climate controller may not be functioning as it should. With both slide full left when the car is started in the morning only air flows from the dash vents. After some driving and the car has warmed up air starts coming out of the defrost vents as well on it own. Movement of the sliders makes not change in air flow that I can tell from any vent. Temperature control workes well hot to cold. If after the air flow starts coming out the defrost vents I push the defrost button on the unit. Air imediatly stops coming out of the defrot vents and is directed out the dash vents only and the air temp goes to warm. Anyoe have any thoughts on what may be the issue?

tjbayless

It appears that the A/C system is these cars is a bit of a mystery as I do not receive much feedback. I will ask one more question that I hope someone out there knows the answer. It appears that my issue is temperature related as when the air temp is cool everything works as its supposed to. Is there an auto function that forces the system into recirculation mode when the outside temp is high?

tjbayless

I am startting to believe that the issue is with the climate control that is installed in the car. i removed it and installed the original form the car missing the control switches and the vent controls work as they are supposed to. I dissasembled the current control unit in the car to check for any loose or broken solder joints and resoldered on that was questionable, but the problem still exists. My next thought was to swap the compressor and defros switch to my original unit to solve the problem. After taking it apart I found that the two units are different. The original unit has slide in switches where the replacement ones are soldered in. I also noticed that there appeared to be muchmore electronics inside of the newer unit. Does any one know if there is possibly a compatibility issue between the two. As I mentioned before, the problem only occurs when air temps are warm. I don't want to buy another replacement unit only to find that it operated the same. I would go the switch replacement rout with mt original unit if the switches were no so expensive. Its hard to pay $250.00 for 2 plastic switches.