Strange flashing lights (and other electrical oddness) in W124
 

I've noticed some strange flashing lights in my W124 when I shut off the car. On the centre console, the bulbs in the switches for the rear dome light and headrest release both start flashing as do the lights in the wheels for controlling the air vents, and I don't think I've spotted that before.

There also appears to be something odd going on with my licence plate bulbs. Both bulbs are fine, but only the left one lights up. I checked across the terminals with a meter and the right one seemed to have no current flowing to it. With the bulb not lit, I'm getting the 'bulb out' warning light on the dash :(

Are these two related? I was thinking that the first one was a failing OVP, but I already have the newer-style OVP, but it could be due for a replacement.

Maybe wiring harness is going south... but wait for a more authoritative response.

Ditto on the wiring harness. If that hasn't been changed, time's up. Even if that doesn't solve it, you needed one anyway.

I replaced my main engine wiring harness in 2005, I can't believe that the new and improved version would only last 2 years, or is this a main body wiring harness issue?

I did some more investigation last night. With the engine running, the car in park with the lights off and the emergency brake on, I had no flickering lights. When I pushed on the brake pedal, the lights started flickering, and the 'bulb out' lamp in the dash came on.

Could this be a switch on the brake pedal that needs replacing/cleaning?

More weirdness is happening... my drivers side headlamp keeps blowing, I've gone through 2 in one week.

One of the bulbs over my licence plate is also out, but when I replaced the bulb the new one didn't light up, and the old one works. I tested the terminals and there was no voltage across them.

The 'Lamp out' warning indicator goes on seemingly at random, when I push the brake pedal it goes on, even though all brake lamps light up (even the centre mounted stop lamp).

Is there something obvious I'm missing that could be causing these symptoms? Would a fuse on it's way out cause all of these problems?

I had the flashing lights syndrome at one point on my 300E. Same type situation in that I would start the car, turn on the lights, and as soon as I touched the brake pedal, all the console and dash lights would flash rapidly.

During this time I was also going through quite a few taillight bulbs on the drivers side. After months of this, and hours of looking at the light assembly, one day I noted a very small piece of the wiring had the insulation torn off. The exposed metal would touch something and short out, blowing the bulb.

Once I fixed this issue, the flickering lights went away.

I suspect you may have a similar issue with your headlight assembly.

Good luck.

Check your charging voltage.. Make sure that the ALT is not over charging things.

This is an interesting thought - how would I go about checking the charging voltage?

I thought this might be the problem, but wasn't sure where to start. I'll take a look at the tail light assemblies this evening (assuming it's not raining, or too cold).

have you positively checked your third brake light and your outer right rear bulb?

Yes, all bulbs have been checked and are still good.

I took my car into my local indy yesterday and they had it all day to try and trace the problem. Needless to say, I'm $700 poorer and still have electrical weirdness going on (but my coolant leak is fixed, and I did have the front brake rotors changed). The tech believes it's to do with one of the relays under the fusebox, but didn't have time to completely trace the problem as I needed the car first thing this morning.

Once again, I noticed that some of the lights on the switches were flickering when I pressed the brake pedal when all the lights were off. All the power window switches flickered (in the rear doors as well as centre console), and the rear dome light switch and rear headrest release. Is there a relay that controls power to the lights in all eight switches and could cause my right licence plate bulb holder to not get any power?

I find it really strange that just one bulb holder out of a pair does not get power, are they really on two different circuits?

I noticed one more thing this morning.

With the engine on and lights off, pressing the brake pedal turned the light behind the LCD in the radio off (but didn't turn the radio itself off). Usually I don't have the radio on so I didn't notice it before now.

Is there a common cause for all these issues?

There should be ....
 

some module under the dash that monitors all the circuits that are part of the "bulb out" warning feature. Maybe that has gone bad?

Electronic parts catalog shows ....
 

something called a "lamp control device" which you may want to check. Possible part number is A0135451328

The wiring for the license lamp is broken at the trunk hinge or nearby. This happens because of the flex of the wiring from opening the trunk (classic metal fatigue) . I had this problem and fixed by splicing out the bad section of wire (the insulation was still perfect, however the copper had broken).

I also have the same problem on my driver door wiring, this time it created a short that kept the interior lights from going off. I cut the shorted wire for the door lamp on the inside of the car rather than rip the door apart. My driver-side heated mirror still doesn't work, probably a related issue.

I would guess your interior lights are not related. The only thing I can think of that would "flash" on and off would be the seatbelt warning lamps, maybe it is related to that.