Quote from Audi Tech. Bulletin (Group:66, Number:99-02, Mar.17,1999):<br>"As a running change beginning January 1999 a thermo-switch has been added to the heated mirror glass.<br>With the ignition key switched ON, the thermo-switch allows current flow to the mirror heating element when outside ambient temperatures are less than 59 F (15 C) +/- 10 F (3 C) and stops current flow when outside ambient temperatures are above 77 F (25 C) +/- 10 F (3 C)."<br>The bulletin further states that these new mirrors are the only ones now available for replacement of defective (burned out) ones, that they can be retrofit to all vehicles 1997-1999, and that they can be fitted individually (i.e. they do not have to be replaced in pairs).<br>Note: There appears to be a typo or miscalculation in the temp. variances shown above.<br>3 degrees C is not the same as 10 deg. F. In fact, 3 deg. C= 5.4 deg F!<br>I'll point this out to Audi!

.<br>

Think about it...<p>3 degrees Celcius is above freezing, which means it must be above 32 degrees F.<p>Regardless, what I think they are trying to say is 15 deg C +/- 3 deg C, so the range would be (12 - 18 degrees C). I don't think they were trying to imply that 10F = 3C.<br>

This is great news, but unless they redesigned the heater grids, I still see the mirrors eventually degrading/burning out again when being on constantly at 60 degress or less. It will just take longer, out of warranty longer.....<p>I just can't believe that they didn't wire them into the rear defroster switch on the '99.5 models where they would probably last the life of the car as pre '97 Audi's did!!!

OF COURSE I was talking about the DIFFERENCE. If anyone read the quote carefully & understood it, wouldn't that be obvious?

I still don't like it. The '96 setup was the best yet with the mirrors linked to the rear defog. Better yet, they should have their own switch as my Subaru SVX did. In the 4 years I had my SVX, I never had to use the heated mirror at all. After a year of owning my A4, I have parked the car outside the garage for a few nights and the mirrors fogged up twice. But, of course, in that year period, my heaters must have burned out, 'cause I drove 45 min. and they still hadn't defogged. So having them on all the time when temps are above 59F seems to still suffer from the burn-out effect over time. Even when the mirrors are fogged, if it had it's own switch (timed would be better), I would guess a 2 minute time interval would defog the mirrors.<p>Also, with their new design, what happens at temperatures from 59F to 77F? From your post it seems that they turn on below 59F and turn off above 77F. So are they on or off between 59F and 77F?<p>G. Hale<br>'98.5 2.8 QMS

It's called hysterisis. You can't spec the switch at a precise temp, there will be variance.

:-)