I have a problem with my lamp out indicator coming on with no reason. Sometimes it comes on when I start the car, sometimes it comes on while I am driving.

I have checked all the exterior lights including the break, back up and plate lights, and all the lights are working.

Any idea what can be causing the lamp out indicator to come on?

 

The light out indicator works off monitoring the current draw.
Most likely corrosion buildup on a bulb contact somewhere.
Vibration can cause an intermittent high resistance causing the current to drop, Ohm's law.

 

Yup, and I found with my last Roadster (had 115,000 on it) that one of the license plate ("tag") lights had become internally intermittent.

I've also seen the clearance marker lights do that. One thing is for sure, you DO have a light out. If it comes on without the lights even on, odds are it's a brake lamp bulb.

 

I had an intermittent light out indicator also. It would rarely come on, just enough to annoy me. Yesterday I was replacing my license plate light lenses with new ones (Mercedes P/N A 230 820 01 66; only about $10-$12 each from a Mercedes parts place). When one of the bulbs came out, the end fell off. It's like the glue holding the metal cap on the end of the bulb is all crumbling, but the wire is still coming out of the glass. I tested with an Ohmmeter, and what's left of the bulb is still good. So I think the wire was making pretty good contact with the cap, and it would almost always work. Then sometimes it wouldn't work. Every time I looked, I never could spot a light out. Hopefully that makes this mystery solved.

 

Mine recently started illuminating after my passenger floorboard was flooded with rain water from a plugged up cowl drain vent hole. That is now cleaned out but the drying out process has just begun. I am hoping it's simply coincidental that a bulb is going out at this time and not a problem from something getting wet other than a light that is causing current draw or resistance on the lighting system. There is no visible bulb out, yet the light indicates something wrong, time to start testing.
My flooding was bad enough that the fan sounded like a prop in the water when I turned it on.

 

A few days later after I thought I fixed it replacing one bulb, my light out indicator came on again, but stayed on. Oddly enough, the other bulb for the license light decided to burn out ! Glad it wasn't the intermittent issue coming back again.

 

My bulb out indicator was correct and simply happened at the same time as water poured in through the hvac fan. The reason I thought all the bulbs were good is because it was the brake light on the driver side. Replaced through the handy access panel in 2 minutes and the indicator went out and has stayed out.

 

My Crossfire did same thing and I got a flood in the pass side of car . I had pulled up the passenger side carpet and I went to the local Dollar store and bought several of those moisture absorbing boxes WOW they do work great . IT took a month but the box was full of water the bottom of the carpet is like a sponge and it took every drop of water out of the carpet and the spongey stuff I kept the carpet lifted and the box sideway the moisture the box absorbed every drop. was a a couple bucks well spent . hope this helps someone !!