Jetsi

Hi all,

2001 A6 Quattro w/2.7T.

The secondary fan is not running at all, even with the AC in maximum. This causes an overheat if not in ECON modeI have looked through these posts and others:

https://www.audiworld.com/forums/a4-...2754421/page2/

https://www.audiworld.com/how-tos/a/...heating-423472

https://www.audiworld.com/forums/a6-...ation-2780763/

I have already checked the 40A fuse and it is good. The fan spins freely so I don't think it is the fan clutch. I only need to drain and disconnect the radiator to reach the service lock position.

Now I am tracing electrical power to see where the fault is at. I see what should be the FCU on the drivers side by the radiator but it appears that the wires for the fan go all the way to an area by the filler cap for the power steering fluid (green cap). I have prodded around there but no changes yet.

Am I missing the wires to the FCU or do they run up the radiator to that junction area?

Thanks in advance.

PS The Bentley is ordered but I have a few days before it will get here.

Harleyguy

Could be several things. There is a sensor somewhere that tells the fan to run; do you have power at the fan cause the fan motor itself could be bad; I don't think the secondary has a clutch, it is driven directly by the electric motor. Lots of stuff here.

Jetsi

The fan should always run when the AC is on, that is what others on this forum have said.

There is no plug at the fan like earlier models so I can't check power at the fan without cutting wires, I will do that if I have to but not if I can avoid it. There is a plug connection by the power steering fluid reservoir, I pulled a brown connector and the fan on the front of the radiator stopped, there is a similar black one but I don't want to test or jump it until I am sure that is it and what polarity the prongs are.

Jetsi

Ok, the Bentley manual arrived today and it has so little information that as of right now I feel like I just wasted $100. It may come in handy later but there is absolutely no information on this fan, it isn't even shown in the schematics.

So unless someone helps me out I will fumble like a blind man for a few days and see if I can get lucky in tracing this problem to its source. After that I put it back together and get it to a shop.

Help me, Audi Wan Kenobi, you're my only hope.

Harleyguy

Maybe see if you can find someone with a VAG Com system to look for fault codes. Otherwise an independent shop would be an option. Also try looking in the sections for climate control or cooling system. I don't have a Bently manual so I can't research further at this point. Try Google and/or Youtube maybe.

georgeb944

Here's the wiring diagram for 2001 fan control... Good luck.

tester123

checked all fuses?

Jetsi

Harleyguy, I don't know anyone with a VAG Com but I will ask around some more. I do have some input on good local and independent shops if I need them.

Geogeb944, that is exactly what I needed. Read why below.

Tester123, yes I checked all of them and they are all good.

So here is where I am at now.

I pulled the black connector I mentioned earlier and tested the connection and it gave me 10.05 volts with the AC both off and on. I am not sure what made me look but with the AC off the electric fan on the front of the radiator was not running and it spooled up when I turned the AC on. So I realize now that the fan that runs when the AC is on is the brown connector right above this black connector.

So knowing that power was getting to the auxiliary electric fan (on the inside of the engine compartment on the passenger side and is not depicted on any schematic) I decided to pull the fan to look at the wiring, figuring either the fan was bad or the wiring was damaged. The wiring looked great so I figured the fan was bad but then thought, isn't 10 volts to the fan low, perhaps? I remember from another thread that the fan was a PWC (sp) and runs like a dimmer. So I jumped the fan to the battery and it fired right up. So now the problem is low voltage to the fan.

Just to check everything out I let the car coolant and oil warm up to operating temperature to see if there were any changes. The plug went from 10.05 volts to 9.35 volts as everything warmed up, not increasing as I thought it should.

So, with all this said and done, I now believe that the problem is either the FCU (unlikely since it supplies power and the AC fan works like it should) or the fan switch in the radiator, labeled as J18, J54, or F54 depending upon the source.

So, armed with the wiring diagram from Georgeb944 and with the information provided in this thread:

https://www.justanswer.com/audi/27d2...ns-normal.html

I am going to let everything cool down and then look into the fan switch. I will jump the wires a to see if the fan operates and then watch the readings on the fan switch as I let the engine warm up to normal temps.

Thanks for the input everybody. I think I will have this figured out tomorrow. Any reference material on the fan switch, such as normal output readings for stage 1 and 2, would be appreciated. My Bentley only tells me switching temperatures.

Jetsi

I typed up a long reply, waiting for it to be approved by moderators for some reason.

Jetsi

Well it appears that it all went into the ether. Lets try this again.

Harleyguy, I have a few recommended shops in mind but I want to exhaust all my opportunities before I put the car back together.

Georgeb944, thanks for that. Just what I needed.

Tester 123, yes I have. Multiple times.

So I pulled the fan that isn't working from the car and traced the electrical line to a junction area by the power steering fluid filler cap. In the process of doing this and looking at a few things I came to the realization that the fan I am having trouble with is not the one that comes on automatically with the AC. That one is on the front of the radiator on the driver side while this fan is inside the engine compartment on the passenger side. So now that we have that information that changes my thinking on this.

I pulled the plug on the bad fan and measured 10.05 volts going to the fan. As the car warmed up it dropped to 9.35 volts. At first I thought the fan was bad since it was getting power but then remember someone in another post saying that the fan worked on something like PWC or similar to a dimmer switch. So I hooked the fan up to the battery directly and it spun like a champ. So now the problem is, why so low voltage to the fan.

This made me think that the fan switch (either J54 or F54 depending upon the source) was the problem. It is in a completely different location on my car than it shows in the Bentley but I pulled the plug off and ran jumpers between 3 and 1 and 2 and 1 which were supposed to make the fan spin. Nothing happened. I thought maybe I was doing it wrong so I picked up a replacement switch off of Amazon for $10, even if it only works for a week if it trouble shoots this then it will be worth it to buy the OEM one later.

Since the fans didn't spin when I put the jumper on the plug I looked at the wiring diagram provided by Georgeb944 and saw that there are four fuses or relays that are supposed to be there. I only checked the big 40A fuse so I opened everything inside up once more to double check. The 40A fuse is the only thing I have, I don't have the relays at 2 and 3 nor do I have another fuse at spot 21.

At this point I am getting ready to throw in the towel. I will replace the fan switch in the radiator because it is cheap and easy and if that doesn't fix anything I am going to put it all back together unless I hear something that gives me another lead.

I am contemplating hooking the fan up to an ignition power source and letting it run whenever the car is turned on so I can drive the car now and get it looked at later.

If anyone has any ideas I am all ears.