Lt. Dan M.

After haveing the battery disconnected for a header and Xpipe install on my 99 A4 coupe, the A/C was hot on the drivers side and 41 degrees on the passenger side. I reset the codes and all was well for a day or two. Then the same thing happened. I again reset the codes and again it was good for a few days. Then it started blowing hot on both sides, with no codes. I did an intake manifold install last week and now it just blows what feels like ambient air out both sides. Oh and I didn't disconnect the battery for the intake install. Today I disconnect the battery and left it disconnected while I ate dinner. Then I reconnected the battery and let is sit for about 10 minutes after which I turned the key on and let the actuators recal themselves. I then started the car and put the air on max and let the car warm up. Nothing but warm air out both sides. I set the passenger side temp to max hot and I got a blast of cool air out of the passenger side. I then set the drivers side for max hot and all air flow stopped. I heard something ratteling in the dash, but no air flow at all. I turned the temp back to max cold and got a blast of hot air then just warm air from both sides again. After that I never got any more cold air out of the passenger side no matter what I did with the temp control for that side. But every time I set the drivers side to max hot the air flow was blocked and when I turned it back to cool I got a blast of hot air followed by warm (ambient) air from both sides. So, I am not sure where to go from here. Is it the head unit gone bad? All the lights work in the head unit and it is sending a signal to the actuators. Is it both actuators went bad? Also, the drivers side air has never been as cold as the passenger side. I have had to add 134a to the system 3 or 4 times since I have owned the car (2005), I have a set of guages and do it myself. I checked the pressure after the header install, added just a small amount, but as stated I was getting 41 degree air out of the passenger side after that, so I am sure it isn't a charge issue. Please help!

dmarkshark

Ok, first off, after reading your post, you need to slow down , it sounds like you are cranking the temp ***** too quickly for the system to be able to respond. Check your codes and post them and you will get the help you need. It is normal for the passenger side to be cooler as that side gets cooler first. Do all of your vents work correctly, can you successfully change where the air comes out, you may have broken the vacuum line? Have you checked the AC fuse in the engine compartment? Just a few ideas to check.

Lt. Dan M.

I know I replied to this onec, no idea what happened. lol The vents swap normally, the compressor is engaging so I don't see how it could be a fuse issue, I checked the vacuum line when I did the intake install and, there are no codes.... now what? ANYONE....

Rj-lo

I cant help you but I am currently experiencing the same thing.
The local vette guy advised to pull the battery to reset the system as a first try..which you did. He said that because he knows about this problem and is somewhat common and costly
Said that its the gears inside the actuators that break and unfortunatley, the gears cant be purchased alone but have to buy the whole assembly. He round about quoted me $1000 to fix the whole thing...fixing even the ones that arent broken because eventually they will break also

Lt. Dan M.

I have seen where you can buy the actuators for $100 each. So for $800 I will figure out how to change them out myself. lol

dmarkshark

So, it has cold on the passenger side, and hot on the drivers? No codes? Not low on freon.
Then its probably the drivers side actuator(broken gear) which is the easier of the two to replace, as you can get to it without having to remove the dash. There are a number of write ups on the forum to do this, but basically remove the seat so you can lay down, take off the lower dash part, move the radio signal(?) box and the actuator is right above it, but it is a tight squeeze, but doable. Good luck! Oh, people have fixed the broken gears and again there are write-ups on the forum on how to do this.

Mrgogo

An AC mech told me to remove fuse #25 in the passenger floor panel. Let it sit overnight and replace the fuse. The idea was that the blend doors had gone out of sequence. When you replace the fuse the system does a diagnostic check and moves all doors to its limits and positions them correctly. Now it could be the actuators have gone bad but this is an easy check. Good luck. It worked on my car.

Lt. Dan M.

I have esentially done the same as removing the fuse by disconnecting the battery, although, I think removing the fuse is a better option. I think my next step will be to remove and inspect the drivers side actuator. Depending on what I find, I will learn how tear the dash apart to remove/ inspect / replace the passenger side actuator. This will not happen until atleast weekend. Good think I am on vacation next week with no plans. I will keep posted my results. Thanks for the help, and anyone else that has suggestions please help.

mrr23

I read somewhere on here that when freon is low this happens

Lt. Dan M.

OK, so, I got the dash out. I can watch the actuators turn the blend door shaft. I take it that means that the gears are not so bad that they arent working. They appear to turn smoothly in both directions. Kinda stumped now. Anyone know where I can get an adaptor to go from R12 gauges to R134? I have adaptors to hook to the car but I cant seem to find anything to connect to my 30# R134 canister. Had a cheep set of 134 gauges but they failed... Any ideas of what to check next or how to hook up my 134 would be appreciated. Thanks

Lt. Dan M.

It looks to me like the actuators are working fine. I can watch the mix doors go full stroke both direction when changing temp with the *****. I did find that the main vent door closes about 90% when I set the temp to 77 and if I raise it more it goes full closed, blocking off all air flow. I checked the defrost and that seems to work fine also. I have found that the pressures are way low. No idea what happened there as last I checked they were fine. I can not seem to get the system to take in any 134. Where do I go with this now?

mrr23

Does the compressor engage when turning on ac?

Lt. Dan M.

Yes, The Compressor Runs

dmarkshark

After you turn the AC on, does the light stay on? The whole time?

Lt. Dan M.

So, apparently there is something wrong with one of my a/c adapters that would not pass any 134. I charged the unit and it is now blowing cold. Still stumped as to why the mode valve is closing the vent door blocking all air flow when the temp is turned up past 77. I think I am safe to put the dash back together though, as everything appears to be mechanically and electrically sound. I will tackle that tomorrow. Still wondering if the head unit is sending false signal to the mode valve and why?

Rj-lo

Mine is going bananas. Today I got both sides to blow cold... Then only passenger side.. Then only drivers side.
The fan control doesn't work either. Just full blast or hardly at all

Lt. Dan M.

So after charging the unit yesterday, all still seems well today. Have not put it back together yet as I want to make sure there is no 134 leaks. I did notice that now the mode door does not close when I turn the heat on.... Was that due to the low charge that the mode door would close when I turned the temp up? Man these things sure are quirky..... Planing on putting car back together tomorrow if all is still well. Also wondering if when the heat was blowing on the drivers side with the A/C running if that could have increased the pressure enough to make the relief lift? No sure but I would think there is a relief valve in the system...