Weird A/C issue...only works when car is moving

**mudd1011** · 09-07-2011 10:25 AM

Hi, I'm having a strange issue, which I noticed earlier this summer but became a real problem today. earlier this summer, I turned on my A/C at a traffic light, and noticed that cold air wasn't coming out. This was at a stand still however, when the car was moving, cold air came out. I was like whatever, no biggie..

But today it became a problem. It's been raining where I live all day and I went out to lunch, but when I got back in my car all the windows fogged up. I turned on the defroster but no cold air came out. I couldn't see out to even start driving. I finally turned the heat on in a parkng space, enough to burn through some of the condensation. I then started driving and right away the cold air came out.

Does anyone know what could cause this issue? I VAG'd the car, but no issues reported.

FYI, I did search, but couldn't find my exact issue.
Thanks

**LowVhighD** · 09-07-2011 10:27 AM

I'm sure you checked this, but are your fans running in the fast mode?

**mudd1011** · 09-07-2011 10:37 AM

I've checked nothing as I don't know what to check or how to check it. What's fast mode? (I have turned on the A/C and sometimes I don't here the click, or change in rpm that normally happens when the a/c is activeated). I've done some more searching and people with similar problems to mine said the culprit was the fan. However, forgive my ignorance, but if my fan is not working, why would I get cold air when the car is moving?

Thanks

**LowVhighD** · 09-07-2011 10:55 AM

When you are moving, the air is flowing through the condenser coils, which is what cools the air. The fans have two modes, a slow and fast one. The fast mode is when both fans are running and you can actially hear them running from outside of the car. Anytime the A/C is on, the fans should be running. Hope this helps.

**Hugh@EuropaParts** · 09-07-2011 10:55 AM

I know my A/C works better when the car is moving... when I'm stopped at a light it doesn't really give off cold air.

**Audibot** · 09-07-2011 11:31 AM

Mudd,

Where in VA are you located? Depending on how far, I could possibly meet up and try to help you out...

**Audi0s** · 09-07-2011 11:35 AM

Originally Posted by Hugh@EuropaParts

I know my A/C works better when the car is moving... when I'm stopped at a light it doesn't really give off cold air.

You shouldnt have such a large drop its immediatley noticeable. You might be a little low on your refrigerant or your fans arent moving quick enough to drop the pressure. Check the fans like mentioned above, make sure you have a low speed when you clock the comrpessor on.

**NIKS07B7** · 09-07-2011 12:35 PM

Originally Posted by Hugh@EuropaParts

I know my A/C works better when the car is moving... when I'm stopped at a light it doesn't really give off cold air.

x2

**pierranchis** · 09-08-2011 06:19 AM

Just got done fixing this same issue. Take a look here.

**bman005** · 09-08-2011 04:30 PM

Originally Posted by Audi0s

You shouldnt have such a large drop its immediatley noticeable. You might be a little low on your refrigerant or your fans arent moving quick enough to drop the pressure. Check the fans like mentioned above, make sure you have a low speed when you clock the comrpessor on.

One of the two is right. The variable displacement compressor will cool with only 50% charge while driving but it just cant keep up when rpms are low. Low charge is most likely...if it were a fan issue you would have refrigerant pressure faults in A/C. With the fans not running and no flow through the condenser pressure will rise rapidly and the system will shut down and if that happens your a/c shouldnt work again until after you cycle the ignition key

**bmc333** · 09-09-2011 09:49 AM

Funny - I'm having this same issue actually. Just started up on me a couple days ago...

**grassrootz** · 09-09-2011 11:42 AM

I think I have this same issue. But instead it turns on after cars turned off with key out the ignition. Almost like its attempt to continue to cool and ran till the battery died. Happened twice. Could a heat sensor be triggering this? It started after Irene blew threw Jersey. Also A/C smells moldy lately after car has sat and I start it also air coming out comes out very slow.

**LowVhighD** · 09-09-2011 11:12 PM

^^I had that issue and discovered that my ECU cover had cracked and the relays were under water. You may want to try drying out or replacing the cabin filter for that mold smell. The filter is on the right side near the windshield. Hope this helps...good luck.

**mudd1011** · 09-10-2011 06:59 AM

That evening, the a/c fired right up when I left work (as soon as I started the car) When I got home, I left the car idling in the garage and was turning the a/c on and off and it did it again. I popped the hood and both fans were turning, so I'm not sure the a/c fan is the issue? I drove down the street in the neighborhood and the a/c started working again. Since that day, I haven't had the issue. I I hooked up my vag tool just to see what measurements are available. There are some for refrigerant pressure, a/c valve something rather, blah blah..My plan was to hook up VAG when the A/c isn't working when I start the car to see what measurements are working if any. Again, not had the issue since, but I'm sure it will happen again. I don't want to take it in now if it's only happening every once in a while..since I'm sure the mechanics won't find a problem. I'll just wait until it happens more frequently and then I'll take it in to replace whatever needs to be replace. I think I can replace the fans myself, although I hear I would have to take the front end off (that looks like a PITA) but if it's the condenser, then I'll probably have that done by others since I assume the system needs more freon afterwards? Thanks for everyone's response

**grassrootz** · 09-13-2011 10:28 AM

Originally Posted by LowVhighD

^^I had that issue and discovered that my ECU cover had cracked and the relays were under water. You may want to try drying out or replacing the cabin filter for that mold smell. The filter is on the right side near the windshield. Hope this helps...good luck.

Will do this tonight. Thanks I will check!

**Charles.waite** · 10-17-2014 04:24 PM

Started noticing this in my b7. Anything definitive on what the fix is on this? AC doesn't do anything while the car is stopped right after I start it up, and will in fact fog up the windows if its really damp out. Once I start driving, and it will literally be within 200 feet of starting to drive, the ac turns cold.

Anyway, I'm not interested in throwing parts at this blindly. Is there a consensus on what causes this?

**kegobeer** · 10-17-2014 04:34 PM

Originally Posted by Charles.waite

Started noticing this in my b7. Anything definitive on what the fix is on this? AC doesn't do anything while the car is stopped right after I start it up, and will in fact fog up the windows if its really damp out. Once I start driving, and it will literally be within 200 feet of starting to drive, the ac turns cold.

Anyway, I'm not interested in throwing parts at this blindly. Is there a consensus on what causes this?

Is your A/C cooling fan (the small one) running when you turn on the A/C?

**Charles.waite** · 10-17-2014 04:38 PM

Originally Posted by kegobeer

Is your A/C cooling fan (the small one) running when you turn on the A/C?

I'll have to check. Hopefully this weekend I'll be able to scope it out. I thought I noticed the A/C being not very cold on my latest road trip, but I came to the conclusion I was making it up. Maybe I was right?

Anyway, I'll for sure check out the fan situation. And a friend just bought a whole AC service kit at Harbor Freight so hopefully I can borrow that from him and see what the pressures are looking like. The car only has 73k miles so I highly doubt the compressor is going bad, but you never know. And I don't remember seeing any damage to the condenser when i last had the bumper off either though I wasn't really looking.

**kegobeer** · 10-17-2014 04:41 PM

Originally Posted by Charles.waite

I'll have to check. Hopefully this weekend I'll be able to scope it out. I thought I noticed the A/C being not very cold on my latest road trip, but I came to the conclusion I was making it up. Maybe I was right?

Anyway, I'll for sure check out the fan situation. And a friend just bought a whole AC service kit at Harbor Freight so hopefully I can borrow that from him and see what the pressures are looking like. The car only has 73k miles so I highly doubt the compressor is going bad, but you never know. And I don't remember seeing any damage to the condenser when i last had the bumper off either though I wasn't really looking.

My A/C really sucked bad, until I noticed that my fan wasn't running at all. Diagnosed a faulty fan (running 12VDC to it wouldn't cause it to spin), and once I replaced it my A/C was running ice cold again. There's also a VCDS check for the A/C fans I think. I'll have to check and find out what it is...but I remember Phil posting about that particular check a while back.

**Charles.waite** · 10-17-2014 04:45 PM

Originally Posted by kegobeer

My A/C really sucked bad, until I noticed that my fan wasn't running at all. Diagnosed a faulty fan (running 12VDC to it wouldn't cause it to spin), and once I replaced it my A/C was running ice cold again. There's also a VCDS check for the A/C fans I think. I'll have to check and find out what it is...but I remember Phil posting about that particular check a while back.

Yea I was just looking that up. I think its an output test in VCDS Engine Module. I might give that a go tonight assuming its not raining.

**Charles.waite** · 10-18-2014 04:23 PM

Ok. So a quick update. The fan is in fact spinning while the AC is on and the engine is running. The fan turns on and off just fine and makes almost no noise so I suspect it's fine.

Out of curiosity I turned the AC an LO and it still seemed like it was at ambient temp just blowing full blast. I then revved the engine to 2000 rpms in neutral and within 3 seconds the AC became nice and cold.

After a bit of googling, to me this seems like too little refrigerant or low pressure in the system. I'll have to do a bit more diagnosis though.

**viziers** · 10-18-2014 04:36 PM

Originally Posted by Charles.waite

Ok. So a quick update. The fan is in fact spinning while the AC is on and the engine is running. The fan turns on and off just fine and makes almost no noise so I suspect it's fine.

Out of curiosity I turned the AC an LO and it still seemed like it was at ambient temp just blowing full blast. I then revved the engine to 2000 rpms in neutral and within 3 seconds the AC became nice and cold.

After a bit of googling, to me this seems like too little refrigerant or low pressure in the system. I'll have to do a bit more diagnosis though.

Sounds like you may be having a similar issue as me. Mine is that the AC only works on cool days and when the outside temp is 75+ the AC blow hot air.. From what I have been told there is a valve in the AC that is not replaceable but there is a company that DOES have parts for the compressor.. In my case it appears that the valve in my compressor is shot.

Both my fans work as well.

The replacement parts are ex014 or ex019 depending which one you have on your compressor (either a snap ring holding it on or a bolt down unit)

Either valve is roughly $60

http://www.polarbearinc.com/PBPC/Hom...mp_Valves.html

vizi

**JayDog747** · 10-19-2014 06:36 AM

Originally Posted by Charles.waite

Ok. So a quick update. The fan is in fact spinning while the AC is on and the engine is running. The fan turns on and off just fine and makes almost no noise so I suspect it's fine.

Out of curiosity I turned the AC an LO and it still seemed like it was at ambient temp just blowing full blast. I then revved the engine to 2000 rpms in neutral and within 3 seconds the AC became nice and cold.

After a bit of googling, to me this seems like too little refrigerant or low pressure in the system. I'll have to do a bit more diagnosis though.

Now that you eliminated the condenser fans, you are low on refrigerant. You need to take it in and have the system checked for a leak. Have you noticed any type of a clatter when you start the car?

**fly300kts** · 10-19-2014 08:20 AM

I just uploaded the Audi Training Course about the A4 B7 Heating, Air Conditioning and Climate Control Systems. After reading this great document, you will be an AC master

http://ul.to/ijensd3l

Phil

**Charles.waite** · 10-19-2014 09:53 PM

Originally Posted by JayDog747

Now that you eliminated the condenser fans, you are low on refrigerant. You need to take it in and have the system checked for a leak. Have you noticed any type of a clatter when you start the car?

Nothing that I can recall, noise wise.

It's possible though that I could have damaged an AC line or the condenser when I was doing the cam replacement though. Or maybe I pulled on a line and momentarily broke a seal and let some gas escape?

Yea I'll for sure look into getting the system recharged though. My brothers old Saab had a really bad leak in the condenser so I have a refrigerant can and some uv dye in my basement I can try out.

**Charles.waite** · 10-19-2014 10:01 PM

Originally Posted by fly300kts

I just uploaded the Audi Training Course about the A4 B7 Heating, Air Conditioning and Climate Control Systems. After reading this great document, you will be an AC master

http://ul.to/ijensd3l

Phil

Thanks. I'll give that a read tomorrow.

I feel like such a nerd but I really love reading those self study guides.

**1killera4** · 10-20-2014 07:02 AM

When mine did that..took a couple of new fans and a fan control module. About a grand installed.

**kegobeer** · 10-20-2014 07:02 AM

Originally Posted by 1killera4

When mine did that..took a couple of new fans and a fan control module. About a grand installed.

Damn! That's about $300 worth of parts and a couple hours work if you do it yourself.

**vvenom800tt** · 10-20-2014 07:56 AM

I just got my new fan assembly in the mail from amazon. $155 with free shipping.

Can i just unbolt the 4 bolts and slide the whole assembly up?

**fly300kts** · 10-20-2014 08:16 AM

Originally Posted by vvenom800tt

I just got my new fan assembly in the mail from amazon. $155 with free shipping.

Can i just unbolt the 4 bolts and slide the whole assembly up?

Yeah right
You need to pull out the front end and still a PITA to replace

Phil

**kegobeer** · 10-20-2014 08:18 AM

Even in the carrier position it's a real pain in the ass to get the assembly out. It's easier if you disconnect the transmission cooler lines. Having done it that way, I totally understand why Phil just removes the front end - it's much easier.

**vvenom800tt** · 10-20-2014 08:19 AM

Deleted

**vvenom800tt** · 10-20-2014 08:20 AM

Originally Posted by fly300kts

Yeah right
You need to pull out the front end and still a PITA to replace

Phil

Thanks phil. I was hoping it wouldn't be too bad :(

**vvenom800tt** · 10-20-2014 08:23 AM

Originally Posted by kegobeer

Even in the carrier position it's a real pain in the ass to get the assembly out. It's easier if you disconnect the transmission cooler lines. Having done it that way, I totally understand why Phil just removes the front end - it's much easier.

I do have a real transmission so no cooler lines to worry about

**Charles.waite** · 10-20-2014 09:19 AM

Originally Posted by vvenom800tt

I do have a real transmission so no cooler lines to worry about

Haha. Good man.

**1killera4** · 10-20-2014 09:40 AM

Originally Posted by kegobeer

Damn! That's about $300 worth of parts and a couple hours work if you do it yourself.

Wrong..It was 500 dollars worth of parts. I bought them all online...then paid my buddy to do the work. Whole front end has to come off the car. If you can do that in 2 hours you should be on a F1 Pit Crew.

**1killera4** · 10-20-2014 09:42 AM

Oh yea...forgot..STFU unless you know what you are talking about.

**kegobeer** · 10-20-2014 09:49 AM

Originally Posted by 1killera4

Oh yea...forgot..STFU unless you know what you are talking about.

Suck my nuts, douche. I've swapped my cooling fans before. Front end does not have to come off - put it in carrier lock position. Your buddy made some cash off you.