tail lights operating randomly

[wzimmerman]

Hi all. 1st post - please be gentle!

My daughter's 2003 Grand Prix SE has a ghost in the machine. The tail lights have been coming on randomly when parked. Has been happening for the past couple weeks. Sometimes they'll stay on all night. Last night, I looked outside and seen that they were on. While walking over there to look at it, they shut off. A little later, I noticed they were on again. Opening and closing different doors didn't shut them off either. Obviously, this isn't doing the battery any good.

I've only done the obvious - like checking fuses, battery connections, etc. Where do I begin to start? Is there a relay which operates only the taillights? Is this something to do with the alarm system? I'm about at the point of tracking down the wires that go to the tail lights and installing a darn switch there just to shut 'em off/on - because I'm getting tired of jumpstarting her car when it's zero degrees outside....

I'd like to try to do something myself because I'm pretty sure a trip to the local GM dealer to fix this is gonna be a $500 bill or so. Anyway, thanks in advance!!

[consultIII]

try jiggling the muti-function switch when the problem is present. If it goes off it might be a bad switch.

As the bulb in question has 2 elements; a bright turn signal/ brake lamp and dimmer tail lamp side, be aware of which element is being turned on.

[wzimmerman]

Originally Posted by consultIII

try jiggling the muti-function switch when the problem is present. If it goes off it might be a bad switch.

As the bulb in question has 2 elements; a bright turn signal/ brake lamp and dimmer tail lamp side, be aware of which element is being turned on.

Seems like a good idea! When it happens, the rear lamps are not the brighter brake lamps. Though, I can't understand why the front lamps aren't on too? Come to think of it, she said that that the headlights actually went off while driving at night last week (yet another grey hair for me). She said she flipped the hi-beam on/off and they came back on. Yep, seems to be a good starting point for troubleshooting. Now, to catch it when it's on....

[richtazz]

I was going to suggest checking the brake light switch on the brake pedal, but since you say it's the lower wattage filament that is lit, I agree the multifunction switch is where I would start.

[wzimmerman]

Apparently, the moon and the stars have to be in proper alignment for the problem to reappear when the vehicle is sitting in my shop. I figure I've already saved a hundred bucks by not having the dealer tell me "we couldn't find anything wrong with it"... so, I'm still waiting...

[wzimmerman]

I almost forgot to update this.

richtazz had it right. Although it appeared that the rear lamp illumination was less bright than the brake lights, it actually WAS the brake lamp filaments that were on .... they just weren't fully bright. The illumination of the third rear window brake light should have been a clue for me.

Nah, I didn't figure it out. I ended up taking the car to a GM dealer out of frustration. They replaced the brake pedal switch. Total cost: $62 which included 1/2 hour of labor. Can't beat that price with a stick! Anyway, thought I'd put this out there in case someone else runs across this problem.