The steering wheel heater worked fine for years. One day I turned it on and it started to get very hot. Control made no difference. Turned off before damage to leather. Tried again later; same results.

Could anyone steer me (sorry about that) to what the problem is likely to be?

 

Pull the fuse out for now, look in your manual for the location or on the fuse cover decal. Not sure what your problem is but it sounds like a possible problem with the climate head unit. Search it out here I've seen that before.

Good luck.

 

Thanks, but I can simply not turn the seat heater on. That works fine. I have done a bunch of searching and reading here but I have not found a helpful answer. Everything i found just said Audi fixed it if it caught fire. I stopped mine before it burned and I don't particularly feel like lighting it off to see if Audi will fix it.

I am trying to get a bit more specific information about what component is likely at fault. I don't know precisely what you mean by "head unit" but I am trying to get an idea of the likely component rather than a major assembly. A transistor failed, a logic module, shorted wiring, etc.

 

How do you know that a simple component is the issue? And how do you know that you "stopped it before it burned"? I mean was it smoking, to what extent are you saying this?

To know a little bit about the steering wheel: it is a bit like the heaters on the side mirrors - they only turn on or off. The seat heater adjuster is just for the actual seats, but it does turn on the steering wheel. jcman was saying that it's often this switch that goes bad and a lot of the times if you replace it you can fix your problems.

 

I dont think Audi will fix it cause its outta warranty! So, pull fuse and check it out. Otherwise get a new heated steering wheel off eBaymotors for cheap.

 

I can see a switch failure making the steering wheel not turn on or off. But that is not the case. Unless there is a built in resistor or other device to control current in the heater, I can't see how a bad switch would cause overheating.

What limits the current (power) to the heater? That should be the part with the problem. I did not spot a device in the manual.

 

IIRC, there was an issue when those cars were new about the steering wheels catching on fire.
I'd search for TSB's and call the dealer to see if there are any open campaigns. You might get lucky.

 

Yes there was. According to the dealer I bought it from, delivery was delayed so they could fix my car.

 

Alternety,
I did a little research for you about this problem on my eBahn manual,
"My first suggestion was to contain anymore damage by pulling the fuse"
that would be #23 for the heater element circuit for the wheel.
The best I could do is attach the wiring diagram so you can possibly identify the problem.

Not bragging here but I'm a twenty-year HVAC/R tech, so all applies:
Contain, Systematic Diagnosis, Remedy----Works for me.

Good Luck Friend.
John V.

 

Thanks. That diagram is what I have been trying to get to in my manual. But my manual is broken.

If you (or anyone else watching) are familiar with Audi wiring diagram conventions, could you please answer a few more questions?

It would appear that the problem is most likely that rectangle marked with what looks like a "K". Whatever is inside that controls the current to the heater.

It would appear that 75x is a +12V bus. Possibly a combination of wire 30 and x. I have not seen that kind of diagram connections before on a "normal" schematic.

I rather suspect that this module is some sort of PWM (or maybe a linear) controller. Linear would probably be cheaper to build in this manufacturing time frame. My interpretation is that there is an enabling signal from the seat switch (E94), power and ground (T2bg/1 & 2).

There st of this assumes that E94 is in truth a signal from the switch and not the heater in the seat. There is a trimmer control on the assembly inside the big rectangle (apparently a PC board inside the steering wheel) that controls the small rectangle. The wheel heater is controlled by this module. If it was simple on/off, this should simply be a relay. That does not appear to be the case. Again, part symbology, but that little "trimmer" could even be a temperature sensor in the wheel.

However I interpret it, I believe that PC board is the problem. It is most likely that the control module applies a reduced voltage to the wheel heater with one end grounded. So even an external short to ground would not overheat the wheel. Likely the same thing with the supposed control signal from the heater switch.

If I had voltage readings for some of those connections/pins I could probably tell what is going on. Unfortunately I don't have a functional system to see what it should look like.

Does anyone have any idea if that small rectangle (control module) is replaceable/repairable, or is it the whole assembly?

And yes, given the relationship of that board with the air bag, I will make sure nothing is powered if/when I go in and fool around with that board.