Heater Blower Fault / Fuse 25

[Josh2109]

Hi folks,

It seems that just in time for the cold weather and condensation the blower motor in my girlfriend's A6 has decided to stop working This makes the car pretty much un-drivable as the condensation is so bad and without air movement from the fan even wiping the screen (greatest of all the sins) clears it for just a few seconds.

Just for info, the car is a 1999 A6 1.8T with dual climate control.

So, a quick check of the fusebox and fuse 25 (30 amp) had blown. I replaced it, ignition on and it blew as soon as the climate control came on. So, I turned the fan down to its lowest setting, and pressed 'econ' to disengage the compressor. I reset the fuse, and turned the ignition on to find the fuse didn't blow. I then cancelled econ mode and set the temp to 'lo', the fuse survived this too. I then slowly increased the fan speed click by click, and the fan came to life and happily blew ice cold air up until about 40% power, where the fuse then blew.

After this I'm thinking that my A/C compressor clutch is fine and so is my blower motor, so it must be the blower motor resistor that isn't working... Apart from that a few sources I saw online state that a car with climate control shouldn't have a resistor pack and the climate unit itself controls the voltage to the fan. That aside I pulled the car apart and lo and behold it has a resistor unit in it




Apologies for the essay, but I just wanted to show my thought process in order to ask; is the resistor unit likely to be my problem here? If so I'll head to the breakers and grab a replacement, but I'd like to save myself a trip if I'm overlooking something else obvious...

Cheers,
Josh

[Josh2109]

Went to the breakers yard today and bought a new resistor and a new blower motor. On the way there and back I had no blower motor or resistor fitted, but I did have a fresh fuse in slot 25 in anticipation of success... Turns out this was a bad idea, as the A6 proceeded to try and set fire to itself in the absence of these parts Even worse, when the new parts were fitted I have exactly the same problem plus my new spontaneous combustion issue

Smoke was pouring out the nearside wing, and having part stripped the arch liner (the bolt into the chassis leg just spins so I can't fully remove the liner ) I have found that the bundle of wires that runs through the wing has melted

Job for tomorrow then, remove nearside wing, repair wiring and figure out what is drawing such a high current, and if it all goes wrong still then have a cry.

I'm really not feeling the love for this car at the moment it has to be said.

Can anyone offer any advice for what might be causing this? Is there anything wired in series with the blower motor/resistor that could draw so much current as to melt wires? Maybe a short somewhere, or a bad earth? I'm almost at the point of pulling my hair out!!

[Josh2109]

I stripped off the wing and bumper today, and I found that one wire for the A/C pressure sensor in the front rad has gotten very hot and burned off all its insulation along its entire length as well as melting anything it contacted It's surprising how much smoke was made by this. Pics below, in the order I traced the wire from where I originally saw the majority of the smoke.


main loom on chassis leg:




Zoomed out to show location:



Bare copper in the loom:



Into the engine bay, these are the connectors below the P/S reservoir cover:





Along the bottom cross member under the rad unit:



And then the pressure sensor (melting stops here ):



Zoomed out to show location:



And to add insult to injury whilst I was rolling around on the cold concrete I noticed one of the fairly new rainsports has a bulge in the sidewall:






So I've isolated the dodgy wire and disconnected the feed to the clutch in the A/C compressor and now I have a working blower motor at least, Next up is to figure out why that wire is getting so hot


Anyone got any ideas?? Has this problem cropped up before?

Cheers,
Josh