Do wing mirror heating elements adjust their temperature (heat output) according to the outside temperature?

 

See "heated seats and heated mirror query".

Never heard of that. Would be pretty complex and pointless.

Never heard of that. Would be pretty complex and pointless.

That's similar to what I thought.

 

Pipsypreturns swears it is true in the post "heated seats and heated mirror query" on page 2 at the moment.

I have never heard of this and would have my doubts, however given the level of electronic trickery on modern cars I wouldn't be surprised if it was the case. 

Edited 2 December, 201510 yr by booke23

No they're either on or off , just glass with basic heating matrix at the back , strip them down and you'll see

Edited 2 December, 201510 yr by blueR36

PTC (positive temperature coefficient) heating elements can take different amounts of current/power depending on their temperature (and so take more if the ambient temperature is low). This is handy as they are self regulating and can't get 'too hot'. This may well be what is being thought of, but all that happens is they get a constant 12V and just do what they do, there's no control other than their own characteristics. No idea if the elements in mirror heaters use this technology, but I know that the washer jets in my '91 Golf does, so it's not new.

You guys are welcome to investigate but from what I know the mirrors are heated completely independantly from the rear screen and the mirror knob has to be in the heating position for them to work.

Most newer VAG cars where the mirror heating is enabled either by the act of turning the switch or on ignition come on at full heat for a 2 min period to ensure demisting takes place but only at temps 20 degrees C and below.

Above 20 they dont heat at all....below that temp they heat as required.....I think a feed from the external temp probe and PWM control of the heating elements is how it is supposed to work.

Essentially they are always on but the heat output is only full for 2 mins after first activation/ignition and then as required...but they dont heat at all above 20 degrees.....so in the summer months where the ambient temp is above 20 degrees they ought not warm up.

Ive seen this discussed on a Tiguan forum and comes straight from the handbook. Given the O2 is of the same sort of generation U cant imagine the tech employed is any different.

I believe the heated washer jets work in a similar manner...they only activate where the temp is 4 degrees or below...when the frost warning is activated.

Edited 3 December, 201510 yr by pipsypreturns

...also people wonder why the adhesives fail and the glass drops out on these....its not just age related...if you think about it if the mirrors are constantly heating to some degree at temps 20 degrees and below that'd do the trick wouldnt it.

Personally I think it would be far easier and a common sense approach if VAG just linked mirror heating to the rear demister but they must have their reasons.

Older VAG cars I believe have a timer so the mirrors for example will heat for 10 mins upon ignition on then switch off after the threshold is met if set to heat...the threshold alterable in VCDS. If you then want them to heat again you have to twist the mirror control away from heating and back again to trigger the timer.