light warning

[jano]

The exterior light issue warning light came on in the dash last week whether I had the lights on or off. My high stop lamp was out, so replaced that, but the dash light was still on. Investigated further to find that my right rear fog light was not working. When I pulled the light fixture, the light was missing. Further investigation yielded the entire mechanism appears to be missing... it's just a hole for the light to plug into, but no thingy present where the light's supposed to touch and gets its power from - it's there on the left side, however.

I'm confused.

What's stranger is when I put the fixture back following the investigation, the light in the dash now only comes on when the lights are switched on.

Eh? Electrical issue?

[MDA]

I'm not sure what the issue you're having with the warning light is about, but I believe the "missing" fog light is normal. I discovered this when I noticed the same thing on my car a while back when I was looking at the rear light clusters. My car is completely stock and has never been fussed with so I surmised that's how they were configured at the factory.

I subsequently read somewhere rear fog lights were only installed on the drivers side.

Hope that helps narrow down some of the possible research paths.

MDA

[gsxr]

There is only a left rear fog light - that's normal.

The bulb which is out may be something less obvious like a license plate illumination bulb, or one of the rear corner marker bulbs. Does the idiot light turn on as soon as the parking lights are switched on? Or do you have to press on the brake, or put the car in reverse, etc before it turns on?

[cstratton]

I have had a similar issue and resolved it by using a different bulb to replace one that worked but was apparently not exactly what the warning light would recognize

[jano]

The light stopped coming on for me now. hmmm.

Dave - I'm assuming "idiot light" is the high stop lamp in the back? If so, it is off if the emergency brake is on, and it turns on in reverse or when I brake. All other lights are operational.

I recall the seller telling me he thought the light switch was faulty, and had ordered a new one, but I'm not certain it was installed, he left me with one in the trunk and it could be new or the old one. *shrug* But appears to be back to normal now, haha!

[gsxr]

Sorry, "idiot light" is the dash light - generic term for any of the dash indicator lights (bulb out, low coolant level, low oil level, etc). If it's off now, sounds like you're all set!

[gerryvz]

It's generally good to get proper European bulbs. I try to use Sylvania/OSRAM bulbs where possible as these seem to be of good quality and maximum compatibility.

Often when the "idiot light" for the bulb-out comes on, it's a small light such as a side marker or a license plate light.

Here's what I do for a quick diagnosis:

a) If it comes on only after the brake is pressed, it's undoubtedly a brake-related lamp. There are only a few of these on the car so it's pretty easy to figure out. Good to have a helper to look at the rear of the car though.

b) If it comes on only after the headlight knob is turned, it's an exterior light. Again it's good to do a thorough walk around of the car as it's easy to miss the side markers on the taillights and the license plate illumination lamps. Obviously the running/parking lights at the head/taillamps are much easier to spot.

Just for future reference anyhoo.

[jano]

Thanks G.

I think I spoke too soon, the light came on again while driving home last night, then turned off after a few minutes, and there doesn't seem to be any correlation to events such as braking or whatnot. I researched the other benz related websites, and my next step will be to make sure all the exterior lights are not only seated properly, but the connectors are clean. I may apply a nip of dieelectric grease as well.

[gsxr]

The most problematic bulbs are the corner marker lights, at the edge of the tail lights. Next time the dash light turns on, hop out and check both sides. If one is off, smack the lens with your fist lightly, I bet it turns on. To fix it, you have to tweak the tabs which contact the bulb. I'd be surprised if it wasn't these corner bulbs causing the problem...

[gerryvz]

Sounds to me (if all of your bulbs are working, verified) that your bulb-out monitoring relay is bad. Replace that.

[jano]

Dave was right, side marker - on passenger side. It goes on off, I think it's loose or just needs a little contact cleaning. :) thanks again.

Just for purposes of edumacation - where's the bulb-out monitoring relay?

[arno]

Dave was right, side marker - on passenger side. It goes on off, I think it's loose or just needs a little contact cleaning. :) thanks again.

Just for purposes of edumacation - where's the bulb-out monitoring relay?

it's high on the right side of the engine bay, long and rectangular. good idea
to remove it and clean up the contacts.

hth,
a'

[gsxr]

The bulb-out relay is located along with most of the other relays, behind the fuses... you have to unscrew the cover (5 or 6 screws?) and remove the cover to access it. It's the largest relay in there. Here is a photo showing the internals - I don't have a photo showing the exterior, but you get the idea on the size... roughly 6 inches long I think: