gaber6

New fans went in and the cluster rebuild is going in on Monday when it gets back. The center LED section was fixed perfectly, but was delivered with the Odometer LED messed up, so another 2 week delay.

gaber6

New Green Temp sensor
New Fan Control Module
New Thermal Switch (in radiator)
New After Run Pump
New Fans
Thermostat has been switched twice
Instrument Cluster repaired
Fuses on top of the battery are spiffy

Fans or AC don't come on at all via the econ button.

WHAT NEXT???
Thanks!
Gabe

gaber6

Cleaned the terminals under battery and on all major wires. No help.

I do have a high pitched electrical sound near the dipstick though when I turn the key to on, when normally the after-run pump would run. GRR.

gaber6

Filled up the freon and the fans do turn on now... Maybe the pressure was low? The AC still blows warm, so I'll doublecheck the pressure again and also put a new Thermostat in.

InTTruder

Did you replace the FCM, or just the fans? Chaeck the thermistor?

InTTruder

Fan fuses atop the battery, under the cover.

Pay no attention to Ryan: he deserted the Staffel!


<JK Ryan!)

gaber6

Yeah in post #32 you can see I replaced all of it..
If the thermistor is the switch located on the driver side radiator then yes..

I haven't had time to switch out the thermostat yet with the brand spankin new OEM one, so we'll see where that takes me..

All the fuses in your image are shiny, clean and new.

gaber6

Took it in to get the A/C recharged. It was at .1 pounds of freon and took 1.6 to fill it back up. I did it at Meineke since it was way cheaper than dealer prices.

They said the compressor worked and blew cold with a jumper, but it still doesn't work via switch. They seem to think something needed to be reset in the computer from Audi themselves... Think it's true?

I replaced the Fan Control Module as well as all the other sensors a while back and wonder if that got toasted before I replaced what was causing the whole mess.

fjasper

I wouldn't speculate, but it seems like a real puzzle, so maybe my rambling thoughts will help.

If you got it filled in November and by January it's low again, there's a leak you should get taken care of. They can put some dye in the system and usually find the leak pretty easily.

Does the radiator stay cool until the engine comes up to temp, then get very hot before the temp gauge starts to rise above normal? If so, the thermostat is probably doing its job. If it's not opening all the way, though, there might not be enough coolant going through the radiator to bring the return temp up high enough to trip the radiator hose temp switch. I think a damaged water pump can produce a similar effect.

I have a 2.7t, but I suspect the fan logic is similar:

lowest fan setting: After-run thermoswitch (also turns on after-run pump) This can be tested by jumping the terminals in the connector to the after-run thermo switch after you run the car and shut it off. Jumping the terminals should make the after-run pump come on (sounds like a quiet fuel pump) and the fans come on at a very low (almost silent) speed for about 10 minutes after shut down.

low fan setting: AC on. This should happen when you're not in Econ mode. I think there's a minimum ambient temp for this, but I don't remember what it is. +5C or something like that.

medium fan setting(?) Low pressure switch(?) This one I'm not certain about at all. It might be the same as the low fan setting above.

high fan setting: Temp switch in the hose coming back from the radiator. This should be testable by jumping the terminals in the connector for this switch, although I haven't done it myself. This one should cause the fans to come on when the coolant coming back from the radiator is too hot, regardless of AC setting. This setting is loud.

If the fans come on when the AC is on, but not when it starts to overheat, then the fan controller, fans, fuses, and wiring are ok. I don't know if the controller can have one speed work when another speed is failed, like the old series-resistor, but I don't think so.

I'm not familiar with the TT system specifically, but the systems I've seen have some kind of switch that turns the compressor on and off based on pressure. If the high pressure switch is telling the controller that the system is pressurized, the controller may never turn the compressor on. I didn't see a pressure switch on your list of things that got replaced. If I'm not mistaken, a low pressure switch also sends a signal to the fan controller to turn up the fans. No freon and a failed high-pressure switch might give you no (AC-driven) fan operation and no compressor operation. Filling the freon might get the fans running, but not the compressor.

That's about all I can come up with off the top of my head. Without looking at a good diagram of the system and understanding the logic, it's hard to narrow it down.

I'll reiterate: I don't know the TT system specifically, so it might be different. And I could just be totally wrong, that happens too.

Good luck.

gaber6

Awesome response..

I have since replaced the pressure switch as well to no avail.

I'll start tinkering with jumping wires and try to backtrack what might or might not be broken. I do have the Bently Manual on my computer so I'll have to find a few specifics.

Maybe since I replaced the Fan Control Module first perhaps something else caused it to go bad, then by the time I replaced everything else, it had blown again.

I saw an output diagram or resistance diagram for the plugs coming out of there at one point and will try to follow that if I can find it again.