Very frustrating, brand new mirror glass still wont work!

[PJayUK]

I bit the bullet and purchased a new mirror glass last week, and finally got round to fitting it this weekend. Although neither of the heated mirrors work on my W220 I thought I would try and replace the passenger one first as I cant stretch to the ridiculous amount of money MB what for the driver side auto dimming one this month!

Previously (about a month ago) I had metered a healthy voltage across the two black wires that connect to the demister contacts on the passenger mirror glass, with the engine running. There was no voltage with the engine off and ingnition on, but I guess the mirrors only warm up when the engines on, but I got a steady voltage when running.

I was looking forward to a nice simple job just remove the old glass and replace with the new one. I connected up the wires to the rear of the mirror fitment they are both black so I assume there is no polarity to worry about. Started up the engine in anticipation and got my trusty meter out…. And guess what!!

No ****** voltage, at all! Turned off and on again and still no voltage and no heat either! According to the external temp gauge on the dash it was 9 degrees, and as far I remember they should work at temps of 15 degrees and below…. I am really frustrated now, confused and out of pocket!

I was just wondering if anyone can offer any words of wisdom to help me decide where to go next with this, before I chuck the glass in the bin!

 

[television]

If the old mirror was open circuit, then it could be possible to have a standing voltage across the 2 wires , but as soon as a load (mirror) is connected it goes back to zero

 

[Blobcat]

Temp has to be below 5' IIRC. I believe some work with the rear demister as well

 

[bigasotonuk]

Hi,
I concur with Blobcat the mirror heater is off because its not cold enough, though i always thought it was 4' that they would come on.

 

[television]

We do have different systems on this on the cars, depending on when they were built, some are linked to the rear window, on little, or no Can Bus cars, and automatic on later cars for the first start.

 

[PJayUK]

How can I find out definitively how my car is supposed to work??

Very difficult to diagnose when you don't know what is normal behavior!

 

[whitenemesis]

How can I find out definitively how my car is supposed to work??

Very difficult to diagnose when you don't know what is normal behavior!

Turn the rear screen demist on, they should always come with that..

 

[PJayUK]

Ok will try that, thanks

 

[television]

Ok will try that, thanks

Dont forget that its on a timer, and if you are going to check the voltage the mirror must be connected to get a sensible amswer

 

[PJayUK]

What do you mean Malcolm?

What controls the time?

 

[television]

What do you mean Malcolm?

What controls the time?

Heated rear window have to be on a timer, owing to the high current consumed.

 

[BlackC55]

They come on 15degress and below.

 

[PJayUK]

Ok got into the car this afternoon to run it round to the tyre place locally, it was raining and 9 degrees. The passenger side wing mirror looked pretty clear so in my excitement I stopped the car on the A322 and lo and behold it was warm!!!! So the god of the three pointed star must have shone upon me and fixed it!

Seriously I did nothing, it was the same temp as yesterday and now its working. The only difference was that it was raining and the car was moving rather than stationary.

So I seem to recall something about a humidity sensor, perhaps my W220 has one and this kicked in.. So quite a happy chap!

I had think about what I have done to my car in the last month so far:

1 New front discs and pads
2 4 New tyres
3 Rear differential oil change
4 Replaced all the interior LED lights
5 New air filters
6 Replacement passenger wing mirror

Quite a bit really, nothing too major thankfully but should see me through the rigors of the M25 for the next few months!

 

[television]

Ok got into the car this afternoon to run it round to the tyre place locally, it was raining and 9 degrees. The passenger side wing mirror looked pretty clear so in my excitement I stopped the car on the A322 and lo and behold it was warm!!!! So the god of the three pointed star must have shone upon me and fixed it!

Seriously I did nothing, it was the same temp as yesterday and now its working. The only difference was that it was raining and the car was moving rather than stationary.

So I seem to recall something about a humidity sensor, perhaps my W220 has one and this kicked in.. So quite a happy chap!

I had think about what I have done to my car in the last month so far:

1 New front discs and pads
2 4 New tyres
3 Rear differential oil change
4 Replaced all the interior LED lights
5 New air filters
6 Replacement passenger wing mirror

Quite a bit really, nothing too major thankfully but should see me through the rigors of the M25 for the next few months!

Look at it this way it gives you something to do, and us

 

[PJayUK]

Exactly, keeps me out of the pub!

For some reason the car just feels worth it, unlike other I have had where it seems to be a necessity. I really hope something big doesn't need doing for a while, I must say airmatic and gearbox do worry me, now that she's seen 118,000 miles.

Still built to be driven that my philosophy!