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Wiring diagram - Ign Switch / console lights

5K views 8 replies 4 participants last post by  43sqd 
#1 ·
2000 ML320 @141K miles, instrument cluster rebuilt last year. I just got the truck back from my son who had it a college for the last couple of years.

Issue: no center console lights when engine is running (ignition switch in 2 position). Lights on with ignition off and the dimmer works fine for instrument cluster and center console back lighting. Turn on engine, console has no lights. Turn engine off and the lights are back.

I have seen several posts with these symptoms, but none indicate a solution. It seems this could be a relay or split power issue and I need the wiring diagram to trace the circuit.

thanks,
Rob
 
#4 ·
There are three distinct sections:

1. the Instrument Cluster.

2. the Center Section of the instrument panel, which includes the radio, the HVAC controls and other switches.

3. the Center Console runs from the back seat up to the Instrument Panel, which includes cigar lighter, shifter and window switches.

Which section are you referring to?
 
#5 ·
Thanks for the information and link.

I need to load it on the desk top to use the bigger monitors.

The section with on/off lights is the center section with HVAC lights and the shifter window switch lights.

Ignition off and headlights on: there is light, but darkness arrives as soon as you turn the key.
 
#7 ·
Sorry for my lack of clarity.

Ignition switch at 0 (key in or out) and position 1 (rotating one step) AND headlights on:
backlighting on the instrument cluster; center section environmental switches and the MCS switches and MCS screen; and center console window switches and gear position indicator all work. The light intensity is controlled by the dimmer and works. The MCS screen intensity is controlled by the dimmer and steps down from full intensity as soon as the headlights are turned on and dims with the dimmer position. All the lights work and dim properly.

Ignition switch at position #2 (rotated to start the engine or not) - only the instrument cluster lights work correctly and are controlled by the dimmer. The MCS screen is at full intensity, the MCS switches have no backlighting, the center section environmental controls and center console gear position and window switches backlighting is off. The dimmer control has no effect on these switches and only alters the intensity of the instrument cluster lighting.

With the ignition switch in position #2, it as if the center section (including MCS) and center console are not getting the headlights on input.

Driving at night for any distance and I must put a paper towel over the MCS screen as the intensity is distracting.

I printed out the wiring diagram and will tape the pages together as I could not follow the traces on the computer as pages flipped.

All solution ideas are welcome.

Rob
 
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