The bulb-out lamp. On my son's 1982 (did I tell you guys we bought another one?) The bulb-out lamp comes on when brake lights are activated, even though the brake lights are good.

Here's what we've tried so far to correct the issue:

1. Found two different brand brake bulbs were in the car, with slightly different resistances. Replaced them with new ones of the same brand.

2. Cleaned the sockets for the brake lamps.

3. Disconnected and cleaned the grounds for the tail lamp assemblies.

What are we missing here? Bad warning module? Where is that sucker? (I should mention, it works fine for the overall bulb-out warning...on for ten seconds, then off.)

Thanks,

Lou

 

Is the parking brake on? Or is the parking brake switch stuck making the system "think" the parking brake is on?

That will do it.

With the parking brake on you hit the brakes and the warning lamp comes on. That tells you that the brake lights are working.

Geeeez. Doesn't *everybody* know that ?? :-) :-)


Cheers
DD

 

Well, yes everyone knows that! But the parking brake is not on, and neither is the parking brake lamp....? Could the parking brake switch still be the culprit somehow?

 

Maybe the parking brake warning bulb is blown? If that's the case, the switch might be "on" but you wouldn't know it.

Anyhow, the switch is on the handbrake lever itself. Removing the plastic cover is tricky but doable with the seat in place if you have a right angle screwdriver. Once the cover is off you can check/clean/lubricate/adjust the switch. The little hold down screws have to be loosened for adjustment...really tiny....like 3mm or 3/64s or such.

You'll see how a little rod actuates the lever arm of the switch. Sometimes just spraying everything with WD40 to loosen the crud and then a good aerosol lubricant will do the trick. Spray the whole mechanism....even down the shaft of the handle. With the little red straw nozzzle thingy you can get some in there at the edge of the opening where the knob pokes thru. In fact, try this before attempting a switch adjustment.

Cheers
DD

 

The parking brake lamp works fine, as normal. Is it still worth it to go to the trouble of cleaning the switch, could it still be the cause even though it is working OK?

 

I'll get back to ya tonight after scratching my chin a bit :-)

Cheers
DD

 

there is a microswitch at the back of handbrake it can be adjusted and or lubed.If its stuck you'll get those symptoms as Doug said
Les
88 1/2 XJ-S

 

Ok, I've mulled. I had to pull out the schematics on this one.

I'd go ahead and clean and/or adjust the parking brake switch on GPs. Can't hurt, and it's free.

However, my gut feeling is that the bulb failure lamp is being turned on by the light green/pink wire from "Brake light failure unit", which is in the console. I'll bet the wires are in a plug which would make pulling just that one wire out difficult. Yould could snip the wire and see waht happens...but snip it where you can easily aplice it back together.

The schematics don't show the inner working of the BLFU so I'm really just guesing.

Cheers
DD

 

You mean it's under the black plate where the shift lever & window switches are? Should I look for a little plastic box with a pink wire, as you state?

Thanks for the help, Doug!!!

 

Hmmmm. Been a long time. I *think* it's actually under the console cubby box, not under the shift lever panel.

DD

 

Doug, you were right, it's at the front of the console/cubby box.

It's made by Smiths not Lucas so I figured there was a prayer of figuring out how it works.

I took it apart. Amazingly simple, really. Two coils (one for each brakelight) wound around two reed switches. When current flows through a brake bulb, it induces electromagnetism in one coil, closing the reed switch for that bulb. If one or the other bulb isn't working, then that reed switch stays open (they are wired in series) and it turns on a transistor (BC337, NTE123AP) which energizes the warning lamp.

Problem: Transistor shorted. But....Having found said module on Ebay for three bucks, it was cheaper to buy a whole module than replace the transistor! At least if all else fails, I can fix this one. Might just do it out of curiousity, anyway.

Thanks,

Lou