C200 rear view mirror assembly

[bog]

Does anyone have pictorial (worth a 1000 words I think) disassembly instructions for the rear view mirror on a Mercedes C200 Part number : A210 810 0317

This issue is that my red LED in the rear view mirror assembly is no longer working; the immobiliser circuit imbalance then can prevent the car from starting.

I would like to mention for those that are stuck as I was that there seems to be a combination of switching the ignition on waiting, switching off the ignition, turning the immobiliser on and off and re-syncing the key fob, (basically about10 minutes of random messing) and you can eventually get a single green flashing led light on the door handle. The car will then start.

I can get the entire mirror assemble off the car ceiling as this is just a sprung loaded clip, pulling straight down or slightly towards one of the doors does the trick. Don’t pull too far down as there is only a short wiring loom attached to the mirror, this has handy male/female connector. Its worth saying that the car will not function at all without the mirror assembly plugged in and it is really difficult to get it back in place as the sprung loaded clip is very strong. To do this I located the left hand side of the clip in place and used a large flat screwdriver to push the other end of the clip back, then a big push from underneath and hay presto…wasn’t easy.

What I need to do is replace the red led but would like to know how to disassemble the rear view mirror unit without damage, also if anyone has the rating for the replacement led that would be fantastic.

 

[bog]

Picture of the mirror assembly, if anyone can help, thanks

 

[bog]

[FONT=&quot]ok never mind the pictures....Any advice on how to get the housing off without damage would be great, at least then I could access the LED...[/FONT]

 

[NW_Merc]

I think there was a HOWTO on it but I cant find it now. Basically if you use something blunt to carefully open up the mirror housing it should unclip, be very careful and patient and it should open up. Don't be too over zealous with prying it open or you'll either snap the housing or damage the mirror inside.

 

[television]

Most of these thing are just clipped together, and by using one of the old bone handle knives round bladed they can be opened.


There are no pictures on this as it is not a normally repairable item.

But as said they can be opened

 

[Diesel Benz]

There are no spare parts for the mirror, the only option then would be that you can fix it. I doubt it would be the led itself and even if the led had failed, it should not make the unit non-functional (you would just not have the indication). There must be something else that drives the led.

But if you can open it, perhaps you can see the issue (cold soldering, corrosion etc.). And if the other option is to buy a new unit, you would not lose anything if you give it a try.

 

[pluggers]

Found it http://mbclub.co.uk/forums/showthread.php?t=32061&highlight=prise

 

[bog]

pluggers and nw_merc thank you.

It is stiff but you just have to be brutal it looks like it was designed to slot together with ease and cause as much grief as possible when taking it apart. I got the same damage being really careful as detailed in the thread and pictures pluggers posted.

Now here’s a thing, I had some LEDS so I played with the dangling electronics before putting it all back together. It works just as well with a new LED as it does totally pulling the old red LED out altogether.

It was just the blown led in place that the immobiliser didn't like!

So if you’re stuck, try just removing the LED. Since then the car has locked and unlocked and started without any errors what-so-ever.

Thanks also to television, yes I tried a stiff plastic spatula but when pushed it just forces the clips further into their respective housings. I had to use a metal knife in the end.

Diesel_Benz, thanks for your input, I take your point on cold soldering. I guess that is possible the base of the red LED looked like a badly soldered repair. This I can't understand as I brought the car from the company I work for and they have owned it from new with all the maintenance done by Hughes at Beaconsfield, (yes, I did ask them to quote for a new replacement unit and I'm still waiting.....)

Anyway a big thank you to mbclub + members for all your help

 

[television]

Thank you for posting back with a happy fix thats the main thing

 

[Diesel Benz]

Great you got it fixed even with some misleading guidance from myself. LEDs like this that would not need to be driven heavily, should live "forever". Would be nice to have the circuit diagram, did you measure the old led with a multimeter, was it short circuited? If it worked without a LED and with a new one, I'm interpreting it does not have a "burnt LED detector" circuit, would not have expected one. I'm guessing the old LED after all was in short circuit mode and was loading the control circuit too much, making it confused.

I guess you'll soon know much you gained from fixing it instead of buying a new unit (the £ part, the experience comes on top).

 

[television]

Great you got it fixed even with some misleading guidance from myself. LEDs like this that would not need to be driven heavily, should live "forever". Would be nice to have the circuit diagram, did you measure the old led with a multimeter, was it short circuited? If it worked without a LED and with a new one, I'm interpreting it does not have a "burnt LED detector" circuit, would not have expected one. I'm guessing the old LED after all was in short circuit mode and was loading the control circuit too much, making it confused.

I guess you'll soon know much you gained from fixing it instead of buying a new unit (the £ part, the experience comes on top).

Just for the record you cant measure LED's with a meter the reading is of no use. the same goes for photo cells. As I am/was working with the things I have only ever replaced 3 in my life, and one was in my own Hi Fi

 

[Diesel Benz]

Just for the record you cant measure LED's with a meter the reading is of no use. the same goes for photo cells. As I am/was working with the things I have only ever replaced 3 in my life, and one was in my own Hi Fi

First, I don't remember if I have ever replaced a burnt LED but when semiconductors fail, they often burn to short circuit mode, then these are more or less a zero (low) ohm resistor and this can be measured with a multimeter.

A reasonable multimeter would also have a diode measurement mode. A led too appears as a diode for this multimeter, at one polarity the meter would measure infinite (high) impedance but at the opposite polarity it would detect the diode conducting. The multimeter in diode test mode would show the P/N-junction threshold voltage, some 0.5 to 0.7 V typically. LED would have a higher threshold like below (from wiki):
Color Potential Difference
Infrared 1.6 V
Red 1.8 V to 2.1 V
Orange 2.2 V
Yellow 2.4 V
Green 2.6 V
Blue 3.0 V to 3.5 V
White 3.0 V to 3.5 V
Ultraviolet 3.5 V

Just took a diode from my drawer and measured 0,5 V forward voltage and 1.5 V for a red led with my multimeter.

Anyway, in this case I was just trying to figure out if the LED had burnt and would then typically appear a short circuit.

 

[television]

First, I don't remember if I have ever replaced a burnt LED but when semiconductors fail, they often burn to short circuit mode, then these are more or less a zero (low) ohm resistor and this can be measured with a multimeter.

A reasonable multimeter would also have a diode measurement mode. A led too appears as a diode for this multimeter, at one polarity the meter would measure infinite (high) impedance but at the opposite polarity it would detect the diode conducting. The multimeter in diode test mode would show the P/N-junction threshold voltage, some 0.5 to 0.7 V typically. LED would have a higher threshold like below (from wiki):
Color Potential Difference
Infrared 1.6 V
Red 1.8 V to 2.1 V
Orange 2.2 V
Yellow 2.4 V
Green 2.6 V
Blue 3.0 V to 3.5 V
White 3.0 V to 3.5 V
Ultraviolet 3.5 V

Just took a diode from my drawer and measured 0,5 V forward voltage and 1.5 V for a red led with my multimeter.

Anyway, in this case I was just trying to figure out if the LED had burnt and would then typically appear a short circuit.

Where as diodes can leak, LEDs well the few that I have had go open circuit. We never measure them the way described it would take too long, If a LED is out, its quicker to measure the voltage present, if voltage there, replace.

I have a HI FI mini on the bench right now where the remote does not work, to get to the sensor is 4 hours, so another job not worth doing.
You cant measure Shotsky diodes that way above as the all have a reverse figure