Hello All,

I am trying to fix an off and on front dome light problem. It works sometimes. The buzzer always works if I leave the key in and open the door. I have checked the front door switches. Looking in my electrical Troubleshooting manual I see a solid state relay the that powers the front dome light.

Does anyone know where that solid state relay is located on a 1985 300D Turbo?

BTW, I can turn on the map light. It works all the time.

Thanks,

bsdguy

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1985 300D Turbo CA Fed 223K

Looks like the solid state relay is in the dome light assembly.

Does the car have a delayed "lights out" function? If so, there is a circuit board inside the dome light itself. It's not a relay, it's an electronic timer. These circuit boards are permanently installed in the assembly, and can't be readily moved for inspection or repair. It may be possible to bypass the function if this is the problem.

That dome light assembly was used in the W123 starting in MY83. The same assembly was used in the 126 in 83, 84 and 85 so you might have a good chance finding one in a wrecker. Part number for it is 126 820 10 01.
Does the passenger side work the same as the driver side? The passenger door switch goes directly to the assembly but the driver side takes a detour through the warning module.
If you confirm that your problem is with the assembly, you might be able to perform surgery on it to disassemble. Might be just a bad solder connection or dirty switch. Does tapping the assembly happen to make it act up?

Hello All,

Thanks for the tips and info. I will take a look in the lite if I can. If I tap on the light it does not come on.

Thanks Again,

bsdguy

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1985 300D Turbo CA Fed 223K

Update on my dome light drama. I removed the dome light the see if I can get access to the diode. I then remembered that I replaced the original front dome light with a used dome light from a W201 from eBay. I looks to be a little more complex than the W123 version.

So I think I will replace the front dome light assembly.

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1985 300D Turbo CA Fed 223K