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Bulb warning light-new thread[200/87] posted by Jason Baugh on
Monday, 9 November 1998, at 2:50 a.m.
Just purchased an '87 240DL. I read the previous thread on the "matching bulb" fix, but it didn't work. Same initial symptoms. Now, when the headlights are off, the dash light comes on only when braking. When the headlights are on, it stays lit continuously. When braking, with the headlights off, the brake lights work fine. When braking, with the headlights on, the right brake light will not come on. All taillight bulbs have been replaced. Observation: the CP32-3 assembly on the problem side is white, while the left side unit is black. Does this signify anything? Is there a mismatch in the wiring? Or, is the assembly bad?
Regards, Jason
Re: Bulb warning light-new thread[200/87] posted by Don Foster on
Monday, 9 November 1998, at 9:05 p.m.
Jason --
There's probably a buncha things to go after -- here's one: Check the entire ground path throughout the taillight assembly (right side, I think you said -- and it's probably one of those stupid, irritating, worthless, useless piece-o-crap flex circuits). Also check to be certain the ground circuit ties solidly to chassis ground. Those flex circuits can be very flaky where they plug into the wiring harness -- I've had to bridge across those connectors with soldered jumpers.
While you may not have a failed ground circuit, you might have poor ground with resistance.
Monday, 9 November 1998, at 9:15 p.m.
Dan,
Thanks for the info. You're right. Today I discovered a bad connection where the harness comes into the assembly on the right tailight. That took care of the brake warning, now the warning light just stays on when the headlights are on. All front bulbs work fine. What do I check now?
Thanks again, Jason
Re: Bulb warning light-new thread[200/87] posted by Don Foster on
Monday, 9 November 1998, at 9:44 p.m.
Jason --
Again, I'd say to check the connections. First, the plug on the bulb. And then back up the harness I think there's another connector -- it might be for ground. Check that for corrosion -- if yes, clean it out and use some synthetic grease to seal it from the weather. Check the ground connection to chassis.
As I tried to explain before, you might have a problem where there's a tiny bit of resistance on one side. This would cut the current by, perhaps, 10% which would trip the warning light, but you wouldn't notice it in the headlight brightness.
Have you recently replaced a headlight bulb? Mismatched bulbs, or even mismatched ages can sometimes create slight current imbalances, triggering that warning light. Does the light stay on with high beams?
--Wednesday, 11 November 1998, at 4:57 a.m.
If cleaning up grounds/contacts doesn't work then try swapping the low beam bulbs left-right. Sometimes the bulb integrity sensor and older vehicle wiring will result in a slight left-right bias. The sensor can tolerate a slight amount of imbalance, but not always. As no two bulbs will ever be 100.000% identical you can often luck out and get back within thetolerance.
Re: Bulb warning light-new thread[200/87] posted by Dave Farrington on
Wednesday, 11 November 1998, at 6:08 p.m.
Hey - those buld integrity sensors themselves do go bad, you know. I've had them exhibit similar symptoms which went awy when the sensor was replaced. fixed the problem, but it was a big mistake. First was the fact that it wern't cheap - try a junkyard first! Second was that it was repairable. Curiosity got the cat and the integrity sensor was opened up. Visual examination faound the slightly browned spot. The ohm-meter said there's no continuity here! Funny thing was that remelting that solder connection and the sensor worked fine.