check panel quest.

[long tall eta]

guys, what causes the check panel lights to come on only at certain times while you're driving? my rear light and license plate light check lights come on after about 10 or 15 miles of driving even when the light switch is off. the lights are working properly though.

[Mo Brighta]

Welcome to the Check Panel World of Weirdity.

The Check Relay has got a touchy side to it, all BMWs of E30 vintage have a failure mode that throws the occasional false negative for (typically) brake, tail, and license plate bulbs. Could be a bad or touchy ground connection, corrosion at the connectors or bulb itself, weak or failed solder flow inside the LKM relay, or perhaps gremlins?

Reed switch components inside the relay are sensitive and can fail intermittently, and that's all it takes to trigger a warning light. They work on current, so if there's a brief drop in current (bump or jiggle caused), that may set it off.

Solution is to clean all connections, tighten all grounds, bend inwards any bulb terminals for better contact force, replace the relay module, or maybe sacrifice a goat ... in lowest to highest cost order.

Trivial solution is to frequently check the lamps it says are out, reassure yourself they do work, then apply electrical taope over the offending warning light ;) (jk, works OK for a Chevy or Jeep)

Another solution is replace the relay from a parts yard and hope that does it.

Mine (E28 535i) has good months and bad months, I just do a visual check when it's having a bad month and that lets me sleep at night.

[Steve Corbett]

Also make sure you have the correct "brass" base light bulbs, not the cheapo silver colored made in China ones.

[reelizmpro]

I think it's the other way around. I find that most problems are caused by corrosion or the wrong base bulbs.

[Steve Corbett]

Your right, my bad!