Question on "bulb out" indicator
 

Hi,

On the '94 E320 I have a little problem. I'm troubleshooting the bulb out indicator and it's leading me down a dead end. Here's what's going on:

A few days ago the indicator came on with the headlights. I checked around and one of the rear corner marker lights was out. No problem. I replaced both with the Sylvania Euro bulbs. The number was 5005 if I remember correctly. Fine, fixed it.

The next day I get the light again. Here's the drill: Start it up, no light. Step on the brakes, no light. Parking lights, headlights, no indicator. When I put it in reverse the indicator lights up. Then it stays on until I shut the engine down and restart. The thing is that both backup light bulbs are working. I can't see anything wrong with that circuit.

Any ideas? Also, before it comes up the license plate lights and third brakelight bulbs are all good. This seems to be somehow related to the backup light circuit.

Thanks!

Take a closer look at the back-up light bulbs. Might have one that is fixing to completely burn out. I always give the bulb a quick flick to watch the filament, ones on the way out will usually break at that point.

I had an intermittant brake light problem. The mounting fixture in the trunk was starting to come apart (plastic separating from metal) and therefore making intermittant contact. Almost always people would see the brake lights lit, but the bulb malfunction light would come on...

-brian

The responses by MikeTangas and md21722 would be a cure to the situation...I have had experience with this and one or the other solution would work.

Usually if the light is about to burn out and you can jiggle the bulb back on, the indicator light should go out. If it doesn't, then the metal track inside your taillight housing(s) has indeed shifted enough to prevent one or more bulbs for getting a solid connection with the associated sockets. That would change the total resistance enough to fire up that dash light (which, btw, is exactly how the system determines that there is a problem).

You can usually press against the track firmly with your fingers near the area that your back-up light bulbs reside, and then try again to see if the dash light goes away...

Thanks for the input. Just to be thorough, I'll pick up a pair of new bulbs and make sure everything is clean and snug. I'll report back tomorrow.

Thanks again.

Check the replacement bulbs are the correct wattage, also check the rear light cluster wiring is propery grounded

Solved
 

Okay, the problem is gone. I replaced the backup light bulbs, cleaned and shined everything up. Either the bulbs were ready to fail or the connection had deteriorated. In any case, things are fine now.

Thanks for all your helpful suggestions!