Heated Mirrors

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Can someone please advise me how they work, the handbook states "automatic" so are they on all the time, or below a set temperature?

The cars a 1998 SLK 230

Many thanks
 
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roadhog

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On any of my cars they come on when you select the heated rear screen.
 
OP
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On any of my cars they come on when you select the heated rear screen.


The same here, all except for a TT I owned and they were on all the time.
 

matthewm1965

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Not sure about the Mercedes system as I have not seen it working yet ! But when I had the Rover 800, they were on all the time, summer & winter. The ones on the Vectra came on with the heated rear window.
 
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Someone has suggested they come on when you use the screen demist function?
 

Blobcat

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Some cars it comes on with the demist, others (later ones) when it drops below 5'C. Today I had the first frost on mine, however as my screen is very clean inside and out it didn't take very long at all for the demister to clear it and the mirrors.
 
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Some cars it comes on with the demist, others (later ones) when it drops below 5'C. Today I had the first frost on mine, however as my screen is very clean inside and out it didn't take very long at all for the demister to clear it and the mirrors.

Thanks for that Bobcat, I was hoping for a reply like that :D
 

television

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The AIR temp and start up circuits come into this, and all CAN BUS driven. The mirror heater is controlled from the door control ECU and is switched on and off by the outside air temp sensor, they are switched on at temps below 5c and switched off at 10c and above. If the widow is opened,then the mirror is switched off, to save energy.

They also come on automatically with the heated rear window
 

Dec

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The best way of knowing under what conditions the come on is by touching the mirror with the back of your fingers, you will feel the heat in the glass after about 30 seconds.

Dec
 

whitenemesis

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As Malcolm says (on mine at least) mirrors come on with the ignition at temps below 5c and stay on to prevent misting up in foggy weather etc..
 
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I diid have the rear screen on for about 10 mins last night, but didn't notice the glass feeling any warmer

I'll try some other senarios tonight.
 
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Dec

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I have never been able to feel the heat in the back window while the heater is on, I think it is a much slower affair, you can really only tell if it is working when it clears the mist, the mirror on the other hand becomes quite warm to the touch.

Dec
 

television

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I have never been able to feel the heat in the back window while the heater is on, I think it is a much slower affair, you can really only tell if it is working when it clears the mist, the mirror on the other hand becomes quite warm to the touch.

Dec

Purely on mass Dec, the mirror is so small compared to the back window plus the mirror is floating, and the window is attached to the body of the card
 

whitenemesis

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The heater must still raise the temp of the glass above the dew point to drive off the moisture.

A colleague had a rear window explode due to a fault in the heater where it didn't auto switch off
 

Lisa Jayne

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Gave my wing mirrors a touchy feely when I got home and they were both definately warm, outside temp 14.5, no rear screen demister on, so I would think that they are on all the time ;)
 

television

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Gave my wing mirrors a touchy feely when I got home and they were both definately warm, outside temp 14.5, no rear screen demister on, so I would think that they are on all the time ;)

No they are not on all the time, they work as in my post 8 they may feel warm but that is only heat that has worked its way up into the housing
 

Lisa Jayne

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No they are not on all the time, they work as in my post 8 they may feel warm but that is only heat that has worked its way up into the housing

Well my passenger side one was almost hot to the touch so just guessed that the heating was on sorry :roll:
 

television

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Well my passenger side one was almost hot to the touch so just guessed that the heating was on sorry :roll:

Maybe it is stuck on or something,,,we have had this question up many times and it has never been answered exactly,,this morning I spent an hour checking on how they work,,and it is the same for all cars.

I will look, at the 170 specifiably later today
 

whitenemesis

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I must correct myself. The temperature I quote was incorrect, should be switched on at temp below 15c and off at temp above 19c :Oops::Oops:
 
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television

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I must correct myself. The temperature I quote was incorrect, should be switched on at temp below 15c and off at temp above 19c :Oops::Oops:

OK so we do have differences in our cars with the on and off temp,,as I said mine are on at 5c and of at 10c,,the main thing is that we now know how they are turned on and off, even if the temps vary,, just shows Peter how much colder your car is than mine:D

I am pleased you found it in the end:D
 

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