light indicator on dash

[Tom Q]

The light indicator on the dash (the one with an exclamation point) has turned on. The problem is my light switch is still off. Does this indicator turn on even if the light switch is off? I checked all my bulbs and all of them are still ok? Does anyone know why this indicator is on? Is there something else I need to check?

[G-Benz]

You should do a search on this as there are tons of threads on this subject.

But the short answer is that your "bulb out" indicator on your dash thinks it's sensing one or more of your exterior bulbs burnt out, when in fact you have a grounding problem.

What I have discovered at one time is that one of the bulb socket strips on one of the taillight housings had sent a fault to the indicator system. And yes, the headlight switch wasn't on, nor did I depress the brake pedal or hit the turn signal switch.

One of the metal rails in the taillight housing had loosened from vibration over time and wasn't making proper contact with ground. So even though the bulbs in that strip that were seated operated normally, it would still set off the dash indicator.

I took some needle-nosed pliers and crimped along the rail until I discovered where the ground breach was located. I did this near each of the bulb sockets. After I found which one set the dash light off, I crimped it down firmly to make sure it seated properly. No more light!

Note, it took months to even consider this solution, so I hope I saved you some diagnostic time...

[Bigmon]

On my 300E it was the right turn signal bulb that burned out.

[tomq]

I could probably guess which light it is. A few months ago, one of my taillights don't light but the bulb is still good. Once I remove the casing and touch the bulb, it turns on. So I guess I will start there.

Thanks so much for the info and yes this will surely save me diagnostic time and $$$$

[haasman]

Also the "light bulb out" indicator system is very sensitive to poor quality bulbs. I went through this, or been there, done that. The system relies on and expects the bulbs to be of a specific wattage and resistance. Other than bulbs meeting spec will often set the system off.

Cheap replacement bulbs are NOT OEM spec. Often the cheap bulbs are made of brass metals.

While looking at Kragens for bulbs over a weekend I noticed bulb packaging with "OEM spec" on them. I have used these repeatedly with good success.

With each acquistion of a car, I always remove all the bulbs. I look for dull yellowed ones and replace them and bulbs with corrosion around the connectors. I use a rag with a very very light coating of WD40 (which allows electrical conduction) and clean them before putting them back.

I always put new bulbs in the license plate illumination sockets because it makes the car appear well at night. New or non-dulled ones also just make the car look fresh at night.

To further the obsession, I remove the light housings and clean the relectors. On older cars it is amazing how much dust and grime accumulates.

I am sure this probably all goes back to almost running into the back of a car at high-speeds in Colorado years ago. Oh, that car's lights were all on but just dull, dim and hardly appeared. I was very shaken by the event. My friends used to laugh at me when stopping for gas at night, I would wipe and wash off the headlights and tailights.

I never have problems with the reporting system. If the bulb-out light does go on, I know I have a bulb out.

Hope this helps,

Haasman

[Tom Q]

your info even makes it more interesting. Last night, I checked my lights and saw that one of them is less bright than the others. That probably means that the indicator is getting a less wattage signal from that bulb. I'll change the bulb later with OEM specs and observe.

Thanks for the info