SL/R129: What is the PCB in rear view mirror area?
09-08-2004, 11:30 PM
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What is the PCB in rear view mirror area?
I would like to know what the very small PCB in the rearview mirror, overhead light switch area does. I suspect it is the timer circuit for the overhead light fade. A chip looks burnt and a new PCB is extremly expensive. I do not want to change it until I know what it does. As the temp sensor is up there as well, it may be for it. My overhead light does not come on with the doors, just manually with the switch.
09-09-2004, 05:13 AM
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1996 SL60 AMG
Rvm Pcb
I thought the PCB in the RVM was a light sensor for the AD (auto-dimming) feature i.e. mirror darkens at night to prevent dazzle from headlights of cars behind you.
09-12-2004, 01:18 AM
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The overhead console constains the lamp switching and the temperature sensor for the air conditioning. There's a small fan (front, centre) which draws air in over the sensor and the electronics is signal conditioning circuitry to translate the sensor resistance (the sensor is a thermistor) into a decent voltage swing which is then transmitted to the air con controller unit in the centre console.
The connector at the rear also supplies power (12v, "Door Open" control line, Ground, Instrument Panel Lighting control) to the lights and the two switches determine which of the two lights is on. The switches each contain two small LEDs which are on when the instrument panel lighting is on to provide a backlight for the switch. There are also connectors on each side to supply the lamps in the sun visors. I do not know if this circuitry also is responsible for the dimming, I would have expected to see more substantial transistors in there to carry the current load of the bulbs if it was in there.
The ony parts you can replace are the lamp lenses/bulbs and the two switches, anything else you need to replace the whole thing and it's expensive, about $250. If you disconnect the connector at the back the air con runs wild (hot) because it's no longer receiving feedback on the temperature.
My housing developed a stress fracture in the housing and because it's so expensive to replace, I put a bead of epoxy resin (on the right) on the inside to hold it together. If you remove this item, it's very important not to overtighten the two screws behind the lamps - the weight of the rear view mirror is carried by its own mounting plate screwed directly to the cant rail so the screws do not need to be especially tight.
The connector at the rear also supplies power (12v, "Door Open" control line, Ground, Instrument Panel Lighting control) to the lights and the two switches determine which of the two lights is on. The switches each contain two small LEDs which are on when the instrument panel lighting is on to provide a backlight for the switch. There are also connectors on each side to supply the lamps in the sun visors. I do not know if this circuitry also is responsible for the dimming, I would have expected to see more substantial transistors in there to carry the current load of the bulbs if it was in there.
The ony parts you can replace are the lamp lenses/bulbs and the two switches, anything else you need to replace the whole thing and it's expensive, about $250. If you disconnect the connector at the back the air con runs wild (hot) because it's no longer receiving feedback on the temperature.
My housing developed a stress fracture in the housing and because it's so expensive to replace, I put a bead of epoxy resin (on the right) on the inside to hold it together. If you remove this item, it's very important not to overtighten the two screws behind the lamps - the weight of the rear view mirror is carried by its own mounting plate screwed directly to the cant rail so the screws do not need to be especially tight.
Last edited by blueSL; 09-12-2004 at 01:30 AM.
09-12-2004, 12:18 PM
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The problem I have is that my interior lights will nto go on with the drivers door, but will with the passenger door. The overhead interior light never goes on and I replaced the switch. Also, the drivers power seat will only work with the key in the ignition, but will work with the passenger door open. So the drivers door switch provides power to soemthing and is not. The switch and wires are good. Do you know what the drivers door switch powers as I need to replace it.
Ron
Ron
