W201 funny domelight problem??? - PeachParts Mercedes-Benz Forum

Jetmugg · #1 10-29-2012, 10:41 AM

Over the weekend, my 190D (later model) developed a strange domelight issue. This is the later style domelight that has the sunroof switch integrated into the overhead console. The car is actually a '93 190E which has been converted to a diesel. Everything has been working fine for several years, until this past weekend.

Anyway, here are the symptoms. With the switch in the normal dome light position (it's a 4 position switch), the dome light will function normally with the key in the ignition switch and the engine running (key in run position). Open the door, light comes on, close the door, light goes off.

However, with the key out of the ignition, or key in ignition, but in "off" position with the key, the dome light will remain ON after closing the door. I started to think maybe there's a problem with the "timer" module for the dome light, as normally the light will remain on for a few seconds after closing the door, but will then shut off. The way it is now, the light never shuts off unless the key is in the run position.

I have resorted to leaving the dome light switch in the "off" position on the dome light control module (overhead).

Has anyone encountered this specific issue? I have read that there is a board which controls the dome light functions, but cannot find a part# or any listing at Pelican parts.

SteveM.

Jeremy5848 · #2 10-29-2012, 12:16 PM

If the 201 dome light is like the one in the 124, and it probably is, the electronics are built into the fixture -- there's nothing located anywhere else. About all you can do is to check all of the connections including the door switches and make sure there's nothing external to the electronics that is making the electronics think a door is open or a switch turned on.

Jeremy

jay_bob · #3 10-29-2012, 12:42 PM

The pins on the fixture are:
30 (battery) note there are 2 pin 30's, one is the power in, the other is the loop through to the visor mirror lights
31 (ground)
15 (switched battery pos II or III)
TK (Tur Kontatk) - door switch - ground this to turn on lights remove ground to start off delay timer.

Jetmugg · #4 10-29-2012, 01:42 PM

Sounds good. I pulled the dome light "cluster" out at lunchtime, and popped the back off. This thing looks as sophisticated as my iPhone. Who knew that a dome light needed an IC chip?

None of the solder joints on the board look bad. I suppose the IC chip or one of the small electronic components (diodes, resistors???) could be bad without any visible signs.

Identifying the terminals is a good start. I'll see if I can do some troubleshooting before I give up and start hunting for a different dome light module.

I pulled both of the driver's side door contact switches. They both "look" good, but I didn't do any diagnostics with a multimeter (yet). I'm hoping that logic will prevail, and that I'll be able to figure this out.

Thanks,

Steve.

Jetmugg · #5 10-29-2012, 01:43 PM

From a pure logic standpoint, I'm betting on the delay timer being the culprit. All other functions work properly.

jay_bob · #6 10-29-2012, 02:10 PM

Note that you have 2 door switches per side up front. One is the dome switch and the other is the power seat switch (allows seat adjustment power if doors open).

If you find the wiring is right, I would be hitting up the p-n-p for a new light assembly...

Jetmugg · #7 10-29-2012, 03:41 PM

Yeppers on the double door switches. I have forgotten which is which (upper and lower), but I believe the one having double sets of red wires is for the seats, and the single brown w/red dots and brown wires is for the dome light.

Steve.

jay_bob · #8 10-29-2012, 04:10 PM

I do not have a diagram for a 201 but there often is a method to the madness.

Red wires are typically constant power
Black wires are typically key switched power
Solid Brown wires are typically grounds, striped brown are the leads going to a switch that grounds the circuit to complete it (like your dome light)

The seat relay switch is on the hot side so it will be red wires
The dome light TK switches to ground so it will be brown wires