Check panel/reverse light issues

[SeriousBusiness]

Since I have had my E30 (1989 325is) I have had issues with the check panel lighting up different things at random. For awhile it was the brake warning, then the license plate light warning. Seems to be something different all the time, so I am just planning on replacing it soon (everytime it pops up with a new light everything is still working).

Now last week I decided to pull the check panel down and just play with it (found out one of the bulbs were not attached anymore) a bit since I was bored on a lunch break. Once I was done I plugged it back in and slid it about half way back into its slot. What I didn't realize was that I had not plugged the harness in all the way, it was just sort of riding in the socket. The fact that my check light didn't flash at me should have given it away but I didn't think about it till later.

On the way home that day my wife was behind me and called to tell me my reverse lights were coming on and off and flickering sometimes. Once I got home I confirmed this.

Since I plugged the check panel back in all the way the problem has not come back that I can tell (flashing reverse lights) but it seems odd that these two things are related like that. Anyone else ever have this issue?

Also, if a bulb on my check panel goes out will it cause the check light to flash upon startup even though there is nothing wrong with the car?

Thanks guys.

[jlevie]

I don't see how the flashing reverse lights and the check panel could be related. That sounds like a problem with the reverse light switch or wiring.

Intermittent problem with the brake light warning can be from a flaky brake light switch or problems with the brake light bulbs. Use of the wrong wattage bulbs, wrong type (brass based instead of the plated base type bulb), corrosion in the taillight assemblies, or aged bulbs can all cause warnings even though the bulbs light up.

[SeriousBusiness]

Hmm, I replaced the bulbs with new ones which all have copper bases, could this cause the check panel to illuminate for those bulbs? I just think its one hell of a coincidence that my problem with the reverse lights was gone after the check panel incident. Its mind-bottling.

[jlevie]

The Check Panel light warning operates off the current draw through the relevant light. Anything that affects the resistance of a bulb can cause the warning light to come on. The brass based bulbs are a problem because brass oxidizes and the effective resistance of the bulb increases. In a like manner if the glass envelope of a bulb is darkened, the filament has lost tungsten and thus has a greater resistance.

The check panel senses current flow via a magnetic reed relay. It has no direct connection to a bulb circuit and thus can't cause a light to flash. In the case of the reverse lights, there is some other problem unrelated to the check panel.

[SeriousBusiness]

OK cool. I'll keep messing with it then, I just wish I could make the car do shit when I can work on it and not when I'm in the middle of something. Like driving. LOL