Tail light bulb receptacle not working, any ideas?

[pryce27]

Hi all,

I just had the bulb out warning light come on, and was notified by a friendly police officer last night that my driver side "running" tail light (the one that comes on when you turn on the headlights) is out.

I changed the bulb but it didn't work. I tried taking the bulb from the passenger side assembly and plugging it in the drivers side assembly, that didn't work either. I tried wrapping the bulb in aluminum foil in case it was a ground contact issue, that didn't help either. I unhooked and re-hooked the wiring assembly and tried jiggling all the parts, but that didn't help either.

I have a voltmeter coming tomorrow so will check if there is any current, but I suspect there is not.

I searched the forums, sorry if I missed a troubleshooting guide for this, but didn't find anything. Any suggestions? Hopefully I don't have to replace the entire panel.

Also- I replaced the outer tail light reflectors and lenses a few months ago with the smoke/red ones rather than the stock amber corners. Looks great but I just learned that there is no cut out for the side-facing corner light in the reflector housing. Has anyone just cut out or carved out a notch for that light so that the side corner is illuminated?

Thanks for the help!

 

[Jlaa]

What kind of car do you have?

Assuming it is a US spec w124 sedan, the bulb out warning light will trip if you do not have any rear sidemarker bulbs installed.

Further - to troubleshoot your driver’s side taillight, put a multimeter across the contacts and measure the voltage. If there is no voltage, start with the wiring near the trunk hinge. You could also suspect the N7 bulb out warning relay under the hood.

 

[pryce27]

It is a US spec 1992 500e.
Thanks for your reply.

 

[gsxr]

You'll need to test for voltage with a meter at the wiring back there, to determine if the problem is at the bulb holder, or further upstream.

Euro-spec tails have no cut out for the side-facing corner light. You can either delete both sides by removing the bulbs (which will not trigger the bulb-out warning), or cut the notch if desired.

 

[luckymike]

I've had trouble with the ground in our taillights. The way the bulb holder array is designed, the ground can be sketchy.

 

[IslandMon]

I had a similar problem and it turned out to be the bulb out relay. Got a used one on Ebay for $20. I think I have a spare if you need one and are located in the US.

 

[dionphaneuf]

I had a manner of electrical issues w my rear lights. Taking them part, cleaning w scotch brite and contact cleaner, and ensuring all the grounds (in the tail light bus bars and in the trunk) were clean and making good contact solved this.

 

[pryce27]

Got the multimeter, and indeed no voltage at the bulb receptacle. Will look into the wiring and the bulb out relay. Thanks everyone for being so helpful.

I will also try cutting the notch for the side lights and see how it goes.

 

[Jlaa]

Was this problem ever solved?

FWIW I was reminded of this problem yesterday evening when my front right marker lights went out while I was looking at it.

I inspected then wiring and swapped the bulb - no dice. Then I swapped the N7 Bulb Out Warning relay under the hood for a known good one and the light came back on. The N7 relay was faulty.

So, I re-installed the faulty N7 relay and noted that if I gently tapped on it, I could get the front right marker light to flicker on.

Then I closely inspected it and noted that the backside of pin x3/7, which supplies power to the front right marker light, had a faintly cracked solder joint. I would have never noticed this unless I were inspecting it with a magnifying glass for kicks.

I resoldered the connection and now everything works again. I have attached the pin mapping for N7 here.