HRJ0383

Hi, I'm new to the forum. In a nutshell, I'm a turbine engine mechanic - mostly Rolls Royce R/3's. I've been having trouble with my A4 and after searching the forums, I can't find any previously solved problems that are exactly the same. I've got an '05.5 A4, FWD, CVT, 2.0TFSI.

I noticed the trouble yesterday when the a/c wasn't working at idle and the motor heated up rather quickly. I pulled over to check the radiator fans and they were acting strangely - they're spinning, but it seems like they start to spin for just a moment and then the motor cuts out and they stop. Both fans do this simultaneously with the a/c compressor on. I know if the fans are spinning that they're getting current, but just to be sure I checked the fuses in the fuse block and the larger fuses behind the lower steering wheel panel. I've got the Bentley manual with the wiring diagrams, and I'm hoping to chase down the problem, but I would appreciate any input from someone with experience repairing this system.

So I know the problem is that the fans aren't spinning as they should be, but is it the fans or the fan control module or something else? I'm about to pick up some electrical leads and test the fans myself, since I haven't got the fancy VAGCOM thing... please, by all means, tell me if I'm making a mistake assuming the input voltage on the fans is 12v. At any rate, any help is much appreciated, I'll do my best to contribute whatever I can to the forum. Thanks ahead.

s4master1

by the description mentioned is the control unit.

HRJ0383

Thanks very much for that. I was in the middle of asking something else but my wife just tl;dr'd me.

I can see the fan module varies the voltage output to control the fan speed, is it ok to test the fans on 12v?

Usually to test modules on aircraft we'll use a multimeter and check voltage output or resistance across plug terminals, is that something I could try here? The Bentley manual doesn't mention it.

HRJ0383

Got around to investigating the module today. I am getting really wacky voltage output from the module, and the fans spin up like crazy under 12v, so it seems that the module is the problem. I haven't been able to find anything to suggest that there is a malfunctioning sensor that is causing the module to behave this way, so I'm going to try and shop down a module. Should be fun to find on Hawaii.

HRJ0383

My replacement OEM fan control module came in today. After installing it, the fans are behaving in exactly the same manner, spinning for a moment and then stopping. I thought the module solution really made sense, but unfortunately that didn't fix the issue.

So... having verified continuity in the circuit, no shorts to ground, proper input voltage etc. I am going to have to start troubleshooting something else.

Relays maybe? If the relay is faulty, could that cause it to open and close like that? Any ideas? I prefer OEM parts, but would I be able to try known good universal relays from the local parts store to troubleshoot the relays? Parts availability is pretty limited on the island. Any replies, thanks for your help.

HRJ0383

Have checked the "614" relay underneath the ECU (per Bentley), it clicks open and closed when 12VDC is applied, no reason to suspect it isn't working. Anyone have any other ideas? This is killing me here. I can't understand why the fans spin just fine when directly connected to 12v but lazily spin 2-3 revolutions and stop when the engine/air conditioning is running, even with a new ($300) control module.

Shanster

This happens to Jeep Grand Cherokees where the auxilary fan does not kick on when the car idling. The auxilary fan is meant to cool the engine when air is not flowing in while the AC unit is on.

The part that needed to be replaced was something called a solid state relay. I'm not an electrical guy, but this was the part my friend (who is a grand cherokee owner) mentioned that needed to be replaced in his own car. I could not tell you if this even applies to Audis but I hope it helps you out.

HRJ0383

Thanks very much for your advice. I took the car to the Audi dealership, and they've confirmed that the fan motors are shot. Unfortunately, the service manager thinks I'm either uninformed or rich or both, and that I should give him $1,600 to fix the issue, $900 of that for parts. I think not.

So, anyone know where I can get replacement fan motors?

HRJ0383

It was the fans. Replaced both, no further issues. SOOOOooo... last week N80 valve, this week fans, next week cam follower, PCV breather and snub mount... at this rate I'll never get to start in on the fun parts.