As said in the title, what causes the brake warning light coming on when the brakes are applied. The bulbs work and the brake lights come on.

It's a 1992 4.0 semi-facelift.

Where is the stoplight brake failure unit and what does it look like. I found one uder the left hand dash but it only has three connectors as opposed to the 5 that are shown in captain cats circuit diagrams. When i pulled the wires off it made no difference.

Confused!!!

 

When you find out let me know. My '84 5.3 is doing the same thing - the brake lights work fine but the bulb failure light comes on when I apply the brakes. Not all bad though, I lost the indicators recently, checked the fuse which was OK, replaced the flasher unit, still no go. Discovered the fuse holder was oxidized, cleaned that (yours has the later fuses) and I was back in action briefly. I noticed that the indicators weren't clicking and then the bulb failure warning light wasn't coming on when I applied the brakes (they are on the same fuse) so I knew I hadn't done a good enough job cleaning the fuse holder - I have now. I wouldn't have known as quickly if the bulb warning light wasn't coming on when I applied the brakes.

 

Anjum. By "brake warning light" are you referring to the red "BRAKE" light on the dash? If so, that could be an indication of a bad accumulator.

 

It sounds like your "brake lamp" check system is active. When you get the "bulb failure" warning lamp as the brake pedal is pressed the system is telling you that the brake lamps are OK.

Weird, I know :-)

However, this should happen only when the the brake pedal is pressed WITH the parking brake being set. The switch on the parking brake lever has a feed going to the bulb failure unit for this purpose.


So, it could be that your parking brake is on or the bulb failure system "thinks" it's on.

Does your parking brake warning lamp work?




The system is sorta confusing yes.

Cheers
DD

 

I've had that happen when my parking brake was not fully disengaged. My bulb failure light works in that situation; my parking brake warning light does not work (that's on the "and when it goes in again" to fix list *sigh*) so the bulb failure light coming on is sort of useful for me. Right now, it's coming on when I put the headlights on since one of the license plate lamps' bulb is out.

 

No it wasn't the brake warning light, would have been worried then!!! The brakes work fine.

Just the bulb warning light so no biggie, the brakes and lights work.

Interesting about the link to the parking brake but too late to do anything about now as it's gone to it's new home.

 

Have you installed LED bulbs in any of the lights as these will cause bulb failure warning.

 

No, the only led bulbs are in the interior lighting.

Haven't found any led replacement tail stop bulbs which say they are brighter than filament ones.

 

The brake lamp sensor is a small module about an inch by half with three wires on it, one monted each side in the trunk near the lamp assembly.
They work by passing the lamp current through it heating up and bending the sensor contact to signal the bulb is working. I have had to pull mine apart as it was not making good contact on the sensor lead, and was also able to adjust it by turning the adjust screw in about half a turn.
No false errors in the last 6 months.

cheers.