AC not working

B6/7 S4/RS4
#1

Hello all. Car is a 07 RS4. Had freon filled twice. Both times by morning it leaked out till empty. but when the right amount of freon was in the car the compressor still never kicked in. Even though it leaks with the right amount of freon in there I would think it should still come on. Pressure switch is brand new. The second time we filled we noticed a distinct freon smell coming from the compressor side of the motor.

Today I took the bumper off and looked around at the condensor and stuff. Nothing seems to look like it’s leaking.

Why would the compressor not even kick on. Is this thing bad? Car only has 55k miles on it

#2

Are you having a professional fill the system or are you trying to do it with a can of freon from auto zone? These cars require a “real” A/C service.

It’s not always easy to find a leak visually unless you have the system injected with UV dye, I would try that to see if the leak is truly your issue.

The compressor not kicking on is a bad thing, but the system may have not been charged correctly if your using a DIY bottle. The system has a pretty good safety protection and if there is an issue the compressor won’t run and burn itself up.

#3

Lol it’s being recharged the right way. Vacuum it out then inject oil and freon. Still not coming on

#4

Sorry man, sometimes you have to ask the dumb questions first. We have been seeing a lot of S4 guys trying to do timing chain jobs without the right tools, manual, and not following the basic instructions lately.

I’d be worried the compressor is the issue. It should have at least kicked on after the initial fill. It won’t go into safe mode until the pressure is really low.

#5

no offense taken here man…yea that’s exactly what I’m thinking. It worked fine on the drive down to sowo for hours then I didn’t use it for about 3 days. Next time I tried…nothing…warm air

#6

All fuses are good. When freon leaks out the econ light stays on like it’s supposed to. Where is the relay located for this?

#7

How can I test the compressor to see if it works?

#8

I’m not sure man, I’d have to dig into the manual. I had a similar issue with my B7 S4, but a simple AC service made it cold as ice again.

I’m not sure it would be a relay.

Do you have VAGCOM? I believe you can check the reason for the compressor shutting off in the modules.

I guess before going the compressor route, I’d have the system injected with dye to verify where the leak is.

#9

Wait, you said it was put under vacuum? A leak would be obvious under vacuum. How long are you keeping it under vacuum?

#10

That’s the other thing. When is out under vacuum the leak test comes out perfect for like 15 minutes. But as soon as pressure is applied it leaks out

#11

I have vag. The only thing it says is low pressure signal but that’s when it runs out of freon. I don’t really know what it says when freon is in there nor have I checked it to see what it says at that time

#12

So I was having similar issue… compressor not coming on even though I had plenty of charge.

Turned out to be the compressor itself, the shaft somehow broke inside the housing and would just spin. It’s probably related to the engine work I had done.

In any case, had the compressor replaced and it’s working now. :confused:

#13

My A/C stops blowing cold after about 15 minutes. The other day it blew a chunk of ice out.

I’m thinking it may have a plugged drain line? Anyone with direct experience?

#14

Never had an issue with the Audi, but drawing on recently rebuilding a nightmare of a 30yr old r12 system, some of the basics still apply here…

To the OP, just wanted to note that on the Audi, I do know that you have to add a specific weight of 134a vs. filling solely via low-side pressure reading…and you shouldn’t have to add oil each time you vac, only if you’re dis-assembling and cleaning out the system.

How long did they system sit flat? Did you replace the dryer before trying to vac/charge? That being said, are you able to get all the way to 30in of vac? If you’re getting low pressure codes, that’s certainly why it’s not kicking on, but when charging it, the system should kick on as soon as you hit the low-pressure threshold. That should’ve answered your ‘is the compressor working’ question…

You should have a temp probe monitoring evaporator temp…if it gets too cold, the system will shut off to keep from icing up. That probe might have failed on yours. I feel like this should be something you can check via vag-com.

#15

I had that problem last year with my B6. Turned out it was low on freon and the evaporator was freezing up.
Charged it up (slight overfill) and no problems since.

#16

Hmmm - that would seem to be too easy! Will have to give it a shot. :slight_smile:

No HVAC errors in vag-com other than my intermittent failing central control valve for vent actuation. If the recharge doesn’t work, I’ll look at this next. Thanks!

#17

I haven’t had AC for 2 years due to a slow compressor leak. Maybe next spring I’ll replace it…

#18

Someone ping Jimmy Bones - he should be able to chime in here and help the OP. I’m sure he’s seen this dozen’s of times when he was a tech.

#19

Tuesday,10,June,2014,17:23:48:19710
VCDS Version: Release 12.12.2

            Address 08: Auto HVAC       Labels: 8E0-820-043.lbl

Control Module Part Number: 8E0 820 043 BM
Component and/or Version: A4 Klimaautomat 2833
Software Coding: 00000
Work Shop Code: WSC 00000
VCID: 6DD1DCC927DD0076401-5106
1 Fault Found:

01317 - Control Module in Instrument Cluster (J285)
79-00 - Please Check Fault Codes

just got this code. filled with freon again and dye for the leak, low psi gone but this now. can it be the compressor stopped working and is leaking?

#20

every time i clear it it comes back