A6 air con fan

**Col** · 25-07-2009,03:18 PM

I've been through this in detail on my last car but it was a 1.9 TDI.

Assuming the 2.7t is the same.....

The next stage would be to unplug the coolant temp switch on the radiator.

It is a duel output sensor so has 4 sets of pins.

In complete silence bridge two sets of pins at a time (bit of guesswork to find which two correspond). The instant you bridge them listen for the relays clicking which are again up above the pedals. Obviously you need to do this in a quiet environment to hear it but it will save you a lot of time.

If you hear the relays click that rules out the control circuits for the fan.

Next stage is to look at the resistor pack for the fan (again assumes 2.7t is the same as the 1.9TDI). The resitor pack is (on the 1.9) located on the underside of the passenger side chassis leg near the front of the car near the rad.

To access it to test, you need to have the undercover off the engine.

Once you've seen it test for 12v at each terminal.

Assuming the relays click, you should get 12v on one of them and then a lower voltage at the other two depending of what the fan state should be i.e low speed

Piccy below of the new resistor pack I had to fit (so you know what you are looking for, again assumes 2.7t is the same as the 1.9))

**Col** · 25-07-2009,03:21 PM

Forgot to say, this was internallt corroded so had to replace it.

About £70 if you shop around.

Bit of a bugger to fit as the front end needs to go into the service position to access the bolts.

But after all the effort, the cooling and A/C system worked faultlessly.

P.S. I also replaced the radiator which was weeping AND the fan which sounded a bit rough.

.........then I sold px'd the car 6 months later for my current A6 !

**Steve2.7T** · 25-07-2009,05:14 PM

Originally Posted by BigCol

I've been through this in detail on my last car but it was a 1.9 TDI.

Assuming the 2.7t is the same.....

The next stage would be to unplug the coolant temp switch on the radiator.

It is a duel output sensor so has 4 sets of pins.

In complete silence bridge two sets of pins at a time (bit of guesswork to find which two correspond). The instant you bridge them listen for the relays clicking which are again up above the pedals. Obviously you need to do this in a quiet environment to hear it but it will save you a lot of time.

If you hear the relays click that rules out the control circuits for the fan.

Next stage is to look at the resistor pack for the fan (again assumes 2.7t is the same as the 1.9TDI). The resitor pack is (on the 1.9) located on the underside of the passenger side chassis leg near the front of the car near the rad.

To access it to test, you need to have the undercover off the engine.

Once you've seen it test for 12v at each terminal.

Assuming the relays click, you should get 12v on one of them and then a lower voltage at the other two depending of what the fan state should be i.e low speed

Piccy below of the new resistor pack I had to fit (so you know what you are looking for, again assumes 2.7t is the same as the 1.9))

That's really great info, thanks! Guess what I'll be doing when I get home!

Only one futher question at this stage....do I need the engine running or just the ignition on to check whether the relays are clicking? I'm assuming just the ignition otherwise I'd never hear the relays?

**Col** · 25-07-2009,05:59 PM

Yes, just the ignition.

When and if you here the relays click on and off when you bridge the rad temp sensor terminals, keep it off.

Reason being you will need to keep them bridged whilst checking for voltage on the resistor pack.

**Steve2.7T** · 25-07-2009,07:50 PM

Sorry to be a pain in the @r5e but just to confirm.....I'm trying to find the temp sensor on the aircon radiator, not the engine coolant radiator right? There doesn't seem to be a sensor in the rad, but it looks like there could be one attached to the metal pipe leading off the drivers side of the rad. Only problem...if that's the one, then it's buried behind the o/s headlight. Hopefully that's easy to remove?

**Col** · 25-07-2009,11:04 PM

No.

You need to look on the coolant rad, not the aircon rad.

Should be (1.9) passenger side near the bottom hose.

**Steve2.7T** · 25-07-2009,11:54 PM

Thanks again. Will have another go tomorrow

**SiliconS** · 02-08-2009,06:15 PM

Originally Posted by Steve2.7T

Hi

I have a 1999 A6. The electric fan in front of the air con radiator under the bonnet never seems to run. Consequently I only get icy cold air con when I'm driving along or if the viscous fan is running when parked up. Should it be running all the time? How can I check it? Is it fused?

Thanks in advance for your help on this one.

Steve

I'm watching this thread - my '99 A6 has the same problem, but I've also got a leaking evaporator so I've got other problems to solve first.

Thanks for all the help that people have contributed to the thread so far.

**eeyore** · 23-08-2009,03:45 PM

Guys

I've noticed recently that my aircon is only running cold when on the move and, sure enough, when I look at the aircon fan at tickover (on a very hot day with aircon on "Lo") it isn't turning.

The good news is that when I hit the fan motor with a bar it springs into life! So, I guess it's the fan motor that's at fault or maybe a dodgy connection inside it.

Does anyone have any experience of fiddling with the motor? Is there anything I'm likely to be able to do with it or do I simply need a new unit?

Also, access looks tight, will I be able to remove the fan without stripping the front of the car or is it a "front into the service position" job?

I'm planning to replace my rattly alternator pulley and service it next week so I could do the two jobs together ideally...

Thanks.

**ScouseNinja** · 23-08-2009,06:52 PM

Originally Posted by eeyore

Guys

I've noticed recently that my aircon is only running cold when on the move and, sure enough, when I look at the aircon fan at tickover (on a very hot day with aircon on "Lo") it isn't turning.

The good news is that when I hit the fan motor with a bar it springs into life! So, I guess it's the fan motor that's at fault or maybe a dodgy connection inside it.

Does anyone have any experience of fiddling with the motor? Is there anything I'm likely to be able to do with it or do I simply need a new unit?

Also, access looks tight, will I be able to remove the fan without stripping the front of the car or is it a "front into the service position" job?

I'm planning to replace my rattly alternator pulley and service it next week so I could do the two jobs together ideally...

Thanks.

Sounds like the bushes in your fan have gone , mine was the same (though on an a4) I replaced the fan and all is well , dont know about the a6 but its not to bad a job on a 99 a4 , I removed the hose between airfilter box and turbo and the fan just about squeezed out.