Heated Door Mirror element

[TDi_B5]

Took my mirrors apart today because according to vagcom they are heated. There are two connections to the mirror glass so I assume the element is encorporated into the glass itself? Mine were very grubby and very corroded so it was no wonder they have stopped working. I cleaned all the contacts but they still wouldn't work. I take it i will need new mirrors with the heated element fitted into them?

[abucksdiver]

Is it worth checking the fuses etc. first?

[TDi_B5]

I checked for a fuse some time ago before I gave up on the idea, couldn't find one so assumed they were not heated. But after running vagcom, it came up with two faults codes, one for either mirror;

00943 - Heated exterior mirror: driver side (Z4)
00944 - Heated exterior mirror: passenger side (Z5)

And after taking them apart and finding to wires going straight to the mirror glass, surely they must be heated? I have an early B5 Passat (1997) which means the heated mirrors are operated by the heated rear screen button, maybe that acts as a fuse as well like the hazard light switch does for the indicators?

[martin1810]

Measure the resistance of the wires in the glass. That will tell you if they can work. Then test the feed wires whilst playing with your switches/fuses etc. That will give you a clue.

[simon hare]

My Bora's drivers side mirror had high resistance across the heated mirror itself (over 1000 ohms across the terminals), the other good side measured 10 ohms. 12v was present at both mirrors with the heated window switch set to on. So i heated the faulty mirror up until warm/fairly hot with a hairdryer, this made splitting the double sided sticky tape easier, (being careful to leave the double sided tape behind on the plastic, not the mirror). Then i looked around for obvious breaks in the heated circuit, using my tester to assist. lo and behold a copper track had corroded away, right next to one o.f the terminals. A blob of solder to bridge the gap and all is working again, albeit, the resistance is lower than the passenger side now at 4.8 ohms (=2.5amps or 30 watts @ 12v!) It does heat up rather more quickly than the passenger side as well now. It was also noticed that the two mirrors are from different batches and the arrangment of the heated wires looked different, hence probably explaining the difference in nominal resistance values. Surely there should be a set standard for this value? Anyway, all is working again

[HAWKS]

If the edges are brownish,then they may of over heated.
My A4 (b5) are auto heated mirrors.I think they run from the tps.I found that they were on constantly,hot or cold weather outside.I changed my tps due to a different fault(not showing warm) an the mirrors are not on all the time now.
just a thought.

[simon hare]

If the edges are brownish,then they may of over heated.
My A4 (b5) are auto heated mirrors.I think they run from the tps.I found that they were on constantly,hot or cold weather outside.I changed my tps due to a different fault(not showing warm) an the mirrors are not on all the time now.
just a thought.

The edges show no real signs of browning or overheating, the mirrored surface is perfect. A greened/corroded copper heater track near to the weather exposed connector was the cause of the failure. My Bora activates the door mirror heaters on pressing of the heated rear window switch, but i'm still not sure if there is an override from the computer/temp sensor, say if the outside temperature falls below a certain level. just to add, i do seem to have a negative offset on the behind front grill sensor of about 4c. The other day it was 22c and the sensor was saying 18c on the dash display, could be of some relevance maybe?

[HAWKS]

Sorry.Its not the tps sensor it was the outside sensor behind the Front grill i changed.

[unclespevie]

just to add that if you leave the adjuster knob in the middle then the heating the glass is all ways on so can burn out the elements quicker.

leave it on the L or R and it will be ok for longer, just put on heater mode when required.

kevin