On my way home tonight, I decided to test the various heated mirror theories; it was about 45F when I left, and I was running errands for a couple of hours. Temp dropped to around 35F.<p>I have a 98.5 2.8QM. Bought it in July.<p>Test 1: Were the mirrors hot after non-snowflake, non-defroster driving? 10 minutes of driving, repeated twice. No. They were stone cold. Of course, they could be burned out.<p>Test 2: As above, but in "snowflake" conditions. Nope, stone cold. Again repeated twice.<p>Test 3: Hit the defroster, see what happens. Try number one, at rest in a parking lot. Mirrors were noticeably warm after less than a minute. Multiple additional tests, snowflake and non; warm mirrors. No doubt about it.<p>Conclusions: My mirror heaters are _definitely_ controlled by the defroster switch.<p>They _may_ also be controlled by some thermosensor, but said thermosensor is not related to the snowflake and comes on below 35F. I do not believe this to be the case, but will test further as the weather gets colder.<p>I thought that all 98.5's we're "always on", not defroster switch controlled. There's absolutely no way I buy that now. Those mirrors were cold - until I hit the defrost switch.<p>So, I wonder if this change is related not to the model year, per se, but to the factory - or to the specific time the car was built? <p>--Greg<p>P.S. Now that we have some cold weather, the heated seats are WONDERFUL. I could not be more pleased with them, except that I wish that they warmed a touch faster!<p>

I'm sure Audi is going broke replacing mirrors. I wouldn't doubt they went back to the '96 and earlier defrost switch control at some point in late '98.

Are they on all the time?<p>Or controlled by rear defroster switch?<p>Or some other way?

Your owner's manual should tell you how they come on.

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I'll check my '99qms and post the result.

Tried the same thing today, and then called the dealer to have him order the parts for both mirrors.<br>I'm almost out of warranty on my '98 already, and getting ready to drive across the northern part of the U.S...<p>Tried putting the defroster on today when it was <35 degrees, and no mirrors. (They weren't warm without the defroster on, either.)<p>HEY AUDI--TSB TIME?? Lets get these things wired up properly to the defroster...my heated mirrors worked great last summer when they were constantly on and it was 80 degrees out! <br>Call Bob Petruska if you need the wiring diagrams... : )<p>Bob--do you think the wiring would be different than yours if I wanted to wire my '98 to work with the defroster too? TIA<p>Rich<br>'98 2.8Q sport, icey mirrors<br>

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I just did a retest - at 25F. Sure enough, the mirrors heated and even managed to melt the frost layer that was on them. So, it would appear that for my car, either the defrost switch or some low-temperature condition (32F?) would cause the mirrors to heat.<p>You rewired yours to the defrost switch and lost the temperature display until you turn them on, right? I wonder if the mirrors are intermittently on to get the temp, thus causing them to burn out?<p><br>

The description of your mirrors' operation is one of *many* possibilities that I have been told by dealers, and probably the one that makes the most sense. You are one of the lucky ones! Unfortunately, the mirrors on my car (and many others) are on all of the time, right through the summer. Perhaps there are defective thermistors involved??? ( Bob, you have the wiring diagrams, what do you think?) <br>Anyway, I just got a new set of mirrors yesterday. The impedance on the defective passenger mirror was >225 ohm (no heating at all), while the driver's was ca. 20 (mildly warm). My new ones were 12 and 6, respectively, and now heat up pretty good after about 30 seconds. <br>Regarding the temperature display, this is off (and comes on with the defroster) if you re-wire the circuit with a relay at the fuse box, as Bob did. Unfortunately, the manual does not tell you that the temperature (and transmission) displays are on the same line (fuse) as the heated mirrors. Lucky for me, I discovered this before I was about to do the re-wire and decided against it. Either way, (and to answer your question) it appears that the display itself has nothing to do with the mirror "burn-out". <p>Tom<br>'97 2.8q

Is this an auto trans thing or am I just too sleep deprived? TIA<p>Rich<br>

It seems that there are many combinations to turn the mirror heaters on depending which model year your own!<p>Rewiring will be a judgement call by the owner...I really don't think Audi wants everyone to go in and cut wires!<p>But it's costing Audi big bucks replacing all these mirrors. You would think that they would come up with replacement mirrors that will last even if on all the time (this could be done). Or place a thermistor in series with the mirror heater . This could easily be located in the front of the mirror housing. Boy would I like to talk to the Audi mirror engineering goup to find out why all these combinations were introduced!<p>Now to really get everyone batty....has anyone checked their heated windshield washer nozzles? These are on all the time also!<p>Let's stay away from that one..............

My '89, 90Q will be 10 years old in April, and both the mirror heaters still work beautifully (Knock on wood). With all the people having trouble with the new ones, I would suspect that the continous heat feature is detrimental to them. Why do they need to be on all the time anyway? Once I activate the defrost on my 90Q, they start to clear up almost instantly. Was this not good enough? <p>Charles<br>

What is definite ironic here.....my '97 rear defroster switch still has the mirror heater terminal on it. They changed the wiring harness!<p>This whole thing puzzles me...I sure wish we could talk to Audi engineering!