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Jake
Jake, Technician
Category: Audi
Satisfied Customers: 2428
Experience:  Over 30 years experience, 17 years with Audi, Factory trained
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I have an 03 2.7t allroad. I am tracking down an a/c issue.

Customer Question

I have an 03 2.7t allroad. I am tracking down an a/c issue. Are you familiar with these?
Submitted: 2 years ago.
Category: Audi
Customer: replied 2 years ago.
2003 Audi Allroad 2.7t
AC issues
Things I have checked:
I have replaced the fan control module and installed new fans (fans work only when direct power is supplied) Electric fans never come on when connected to the fan control module
I have replaced the coolant sensors (one in the lower radiator hose and one on the back passenger side of engine)
The ambient temp sensor is working correctly
If I supply 12v to the one wire going to the ac compressor it will turn on and work but fans never come on.
I have located the high pressure switch but I do not know how to test it.
Customer: replied 2 years ago.
I think I have located the AC relay but I am not entirely sure it is the right one. I have not been able to find the AC fuse (supposedly 40amp) to check it.
Expert:  Jake replied 2 years ago.
Hello, I think you may be getting a bit ahead of yourself on the diagnosis here. First let's start with the problem.
I assume based on your description that the a/c is not getting cold and the fan does not come on 1st speed when "AUTO" is selected. Is that correct?
The first and most likely thing to check here would be the refrigerant charge. It will require an a/c machine or gauges to check. When you hook up to a system you should have approximately the same pressure on the high and low side and it should be a little higher than the ambient temperature. So on an 85°f day, you should have approximately 85 PSI pressure. With the vehicle running and a/c active the high side should cycle up to about 175 PSI and the low should cycle down to about 35 PSI.
Typically a low charge is the most common reason for the a/c not to get cold. The pressures when you hook up are a little lower, when you evacuate the system it will be about 1/2 lb low on charge so the low pressure switch will not allow the a/c clutch to engage. Once evacuated, held in vacuum for a period of time (dries the system), and recharged with the proper amount of refrigerant the system works well again. I advise you DO NOT add a can of refrigerant from an auto parts store as it does not do a good job.
If you can't get it to a garage to check the a/c, but you have access to a VW/Audi scanner (VAGCOM) you can check for stored DTCs (Diagnostic Trouble Codes) in #8 climate control. There should be an associated code to go along with the inoperative a/c.
If the problem is not what I have described, and there is something else going on, please let me know along with any other details you may have or things you have done and why. The quality of my answer is directly related to your description, so please be a complete and detailed as possible.
Thank you!
Jake "The Audi Doctor"
Customer: replied 2 years ago.
I added some notes you may not have seen yet.. Please look at those.The a/c system was charged last week by a tech and we could not get it to cycle on. It has the correct amount in it and does cool when you jump the ac lead to power. The electric fans never come on, engine cycle or key on, etc. They do come on if you wire them directly to power.
Expert:  Jake replied 2 years ago.
Yes, i saw everything.
Some basic check that should be done first:
1. With the vehicle running and the a/c turned on, check all the fuses on the left side of the dash with a volt meter. Check both sides of each fuse. Each fuse should have system voltage (about 14v) on both sides of the fuse. If there are any fuses without any voltage on either side let me know the fuse number(s).
2. Inspect the wiring and connections under the cover in the left front of the engine compartment going to the compressor and fans. It's the black plastic cover in front of the coolant tank and next to the power steering reservoir. The single wire, green connector goes to the a/c clutch, the biggest ones go to the fans.
3. You say the fans never come on. How do you know for sure? It would be rare for both the a/c compressor activation, and the cooling fans to fail at the same time. If the vehicle is at operating temperature and idling, will the fans come on? If the mechanical fan keeps the vehicle at normal temperature, try covering the grill with a towel to restrict air flow while carefully watching the temperature gauge. It shouldn't reach the 3/4 mark with out the primarily electric fan turning on.
The next step would be to scan the #8 climate control module for any stored DTCs. Let me know what the code(s) are and I can further assist you. You can't do the electrical tests manually to determine the cause. You need the onboard diagnostics to identify the circuit invoked causing the condition.
As you're learning it's expensive to "throw parts at it" and see if it will get fixed. Did the mechanic recommend replacing all the parts thus far, or was it your decision? If it was the mechanics idea I suggest trying to find another shop to work on it. That's what we call a "parts swapper". Someone that doesn't know how to diagnose it so they just keep replacing parts. As an owner sometimes it's cheaper just to try changing some parts, especially if there is a "pattern failure" of parts that typically fail. Most problems are pattern failures, but if what you have told me so far about the compressor and fans, there is no pattern failure except for the main fan (next to the mechanical) to fail.
Let me know how you make out. BTW, not only am I familiar with this vehicle I own and drive the very same year/model Allroad.
Thanks!
Jake
Customer: replied 2 years ago.
1. all fuses check out ok.
2. I checked the cabling and also replaced the control module with no change. I supplied power to both fans and they turn on manually. I also unplugged the green wire and inspected it. I gave it 12v and the compressor came on.
3. The mechanical fan works but I have never seen the electrical fans come on (is there anything I can try to see if they will come on besides hard wiring them)I only replaced the main items that normally fail. after than I started doing more research. These cars have some complicated fan systems!!BTW.. .My allroad is a Stage III 6spd with 3 piece wheels. Its sweet!
Customer: replied 2 years ago.
when I pull the 267 relay out what should I be getting on the four connections with econ on and off? Maybe that will show me something else. I will also get Vagcom and check it out as well.
Expert:  Jake replied 2 years ago.
I don't know about the relay. The problem with testing like that with computer controlled systems is that the the wiring diagrams can't show the inter workings of the control module/head. So you don't know how exactly it is to function. That is why it's important to isolate the circuit. When checking with the VAGCOM it will identify a circuit. Then you check that circuit. If there are no codes it's likely the control head. I have replaced a dozen or so over the years. This has been the biggest pattern failure over the years. You might want to start calling auto dismantlers to see if you can get a good price of a used one. If there are several codes I suggest you erase them and see which codes come back.
To test the fans do as I have suggested in my previous answer and drive the vehicle to operating temperature then let it idle and cover the grill (inlet air) with a towel or blanket. Watch the temperature gauge closely and listen for the fan(s) to come on. It/they should come on before the gauge reaches 3/4. I really would like to see you test the fans as I can't imagine one problem that could take out the a/c compressor request signal and the cooling fans (engine temperature management) at the same time.
Thanks!
Jake