Bulb Out Warning Light Won't Go Off


Been having some issues with the light. For some time, it seemed to be taking longer and longer to go out, after the headlights were activated. Then for awhile it seemed to operate normally. Now it has come on, and won’t go out whenever the headlights are on. I have checked all external lights and they are all operating normally, so I am puzzled why the warning light won’t go out. :confused: A week or two ago I did install LEDs for the inside back side lights. I also tried to install LEDS for the high stop brake light bar, but they weren’t the right type, so I had to put the old bulbs back in the strip. However, I think the warning light problem started even before then. Also, IIMU, that those lights are not on the failure warning circuit, being interior lights.

So, assuming one of the BFMs has gone bad, do they usually do so with the heated metal strip in the “light on” position?

(Kirbert - author of the Book, former owner of an '83 XJ-S H.E.) #2

Yes. They are “normally” in the warning light on mode, and the heat from the current causes them to bend and open the circuit.

One mode of failure of anything with a bimetal strip – which is what those BFM’s have inside – is that one side of the bimetal strip can corrode completely away. It still looks intact because the other half of the strip is still there, but it will no longer distort with heat. Something to think about in a vehicle this old.

As has been mentioned before, the BFM’s are adjustable. Long slender threaded screw sticking out the bottom. Turn on the lights, let them sit long enough until everything is warmed up, then adjust the screw just until the warning light goes out.

(Aristides Balanos) #3

I think that they are at least four of them, so you have to short each one until you find the bad one…
If you have no luck and you can’ make them work by adjusting them, I have some spare ones.
PM for details.

(sixcyl) #4

Double check that the two number plate lights are working correctly, one of those out will trigger the bulb failure unit.


Did that. Yes, ALL outside bulbs check out. Thanks, though.