heated mirrors - what causes them to power up ?

[X5-D-Sport]

heated mirrors - what causes them to power up ?

Do they come on with the heated rear window ? or is there a temperature sensor that does it automatically ?

[X5Sport]

Heated rear window.

[snrbrtsn]

Mirror heating is individually controlled by the computer modules in each front door - following a program that uses the outside temperature as reported from the OBC. Power is applied in 4 different stages (percentages of time) to give 4 different degrees of heating - all according to temp.

Temp Range % of Time
below -10C 100% (totally on)
-10C thru 0C 75%
0C thru 15C 50%
15C thru 25C 25%
above 25C 0% (totally off)

There is no manual control of their operation.

Also - the washer nozzle heating is controlled in a similar way - but there are either on or off (single stage). They start to heat when the temp drops to +3C (same time as you get the "freezing temp" alert message). They turn off when the temp climbs to +6C.

Both these heating functions, like many other non-essential functions, will be shut down if the battery voltage falls too low (below 11.4) and will not be re-activated till the voltage goes to about 12.2.

Note - if you loose the temperature sensor for the OBC, the reading defaults to -40, at which time your mirrors and nozzles will be stuck in full heat

[X5Sport]

Well the heated mirrors on my E53 (and E71) only come on if the heated screen is on.  Was there an option that changed that to automatic?  I'm almost certain our E46 is the same, but I haven't used it in Winter for a couple of years now so cannot be 100% positive that is the case.

It could of course be that because I tend to put the HRW on immediately and it all happens at the same moment, that it 'appears' that they are all linked to the switch?  I have never driven with a frozen screen and seen the mirrors thaw  :-[

[kkx5]

E53/e39/e46 does is as "snrbrtsn" states, no control over it by us.

[X5-D-Sport]

Now I have the answers - thank you yet again gents - appreciated.

I swapped out both my door mirrors, the drivers OEM with the dimming option still works, but I never paid much attention to it...

What is an OEM drivers door mirror worth to sell it do you think with the dimming function ?

[henrym3]

So, basically in this country they are permanently on. Don't see it above 25c that often At least 15 mins in every hour.

[Huxsta]

[quote="X5-D-Sport Salisbury"]
Now I have the answers - thank you yet again gents - appreciated.

I swapped out both my door mirrors, the drivers OEM with the dimming option still works, but I never paid much attention to it...

What is an OEM drivers door mirror worth to sell it do you think with the dimming function ?
[/quote]
If it's an e70 model the drivers side mirror glass is approximately £320 from the dealership!

[Huxsta]

Also the e70 mirrors are fully automatic with demisting without touching anything else as per e39/e46 etc etc.

[grumpywurzel]

Could've sworn mine came on with the rear heater.... when they used to work  :wall: