Bulb Out Warning Light When Brakes Applied??

[Laird Scooby]

Originally Posted by Steve 940

Re post from Ginger Magic.

The mention about the towbar got me thinking, not always a good sign......

When I picked the car around a month ago there were no lights on the dash, but after hitting my shins on the tow ball a few times, I noticed it had a lever, and simply removed the tow ball, popped on the plastic cover that I found in the left hand boot cubby hole, all sorted and no more effing and jeffing about skinned shins.

Is it possible that the bulb warning sensor somehow is expecting a signal of bulb in the towing electrics?? If so, any pointers to identify would be greatly appreciated.

As far as I know, I didn't touch the socket for trailer electrics when I removed the ball hitch.

Cheers
Steve

If the towbar electrics have been wired in correctly, the tail and brake lights will take their feeds from upstream of the BFU so shouldn't effect it either way. That means when you are towing, the BFU will still work on the car only.

However if someone has decided they can simply splice into the light circuits in the back of the car, they may have caused problems, not least with the BFU itself.

[kiloran]

Re towbar electrics. I don't think so, based on the fact that a blown brake light bulb on my bike carrier (standard 7 pin electrics, factory-fit towbar) didn't throw a warning light on the dash.

[Laird Scooby]

Originally Posted by kiloran

Re towbar electrics. I don't think so, based on the fact that a blown brake light bulb on my bike carrier (standard 7 pin electrics, factory-fit towbar) didn't throw a warning light on the dash.

It won't if the towbar electrics have been fitted correctly - see my comment above.

[Skyedriver]

Just to add to everyone elses post, my car has done this for the last 5 years or more off and on. Happens about once a month. Just accept it now, all the lights work correctly.

[deeman940]

i had this problem, was due to an aftermarket rear light and the bulb holder not seating properly and one of the contacts arcing out....solved it by buying a s/h genuine unit with holders

[Laird Scooby]

Originally Posted by deeman940

i had this problem, was due to an aftermarket rear light and the bulb holder not seating properly and one of the contacts arcing out....solved it by buying a s/h genuine unit with holders

Any idea what brand the aftermarket cluster was Damo?

[loki_the_glt]

Don't forget that you can check th brake lights with the ignition off; all you need is a dark location and check your mirrors for a red glow. That eliminates the tail lamp element of the dual-filament bulb from the equation.
It's a simple point and one that's often forgotten when testing stop lamp circuits.

[Laird Scooby]

Originally Posted by loki_the_glt

Don't forget that you can check th brake lights with the ignition off; all you need is a dark location and check your mirrors for a red glow. That eliminates the tail lamp element of the dual-filament bulb from the equation.
It's a simple point and one that's often forgotten when testing stop lamp circuits.

While that's true, it only gives a simple go/no-go test for operation, it doesn't give the opportunity to observe slight differences in brightness that the BFU is picking up on due to slightly different currents running in each leg of the circuit. A useful test nonetheless. A broom can come in useful too, handle through the steering wheel onto the brake pedal, adjust the seat backrest to push on the head of the broom to operate the brake pedal to bring the brake lights on. (A similar length of wood can also be used, a broom is a good descriptor for visualising though)

[Badger vs Bodgers]

I had this exact thing earlier; turns out I'd knocked the earth contact at the top of the rear light cluster. It was fairly loose anyways, so that may have contributed.
I used a small screwdriver to gently reshape the contact so it clamped better and it seems to have sorted it.

[AllHailKingVolvo]

This was an issue on the NS rear cluster on my petrol 940 until recently and has just started happening on the Derv also.

I chased my tail for a bit cleaning contacts etc but eventually solved it on the petrol car by replacing the Lucar connectors on the cluster-the old ones were loose and one of them must have gone high resistance somewhere. Zero problems since the fix.

I’d suggest looking into that next as you’ve already cleaned up the bulb holder connections. The whole assembly tends to be a bit finicky connections wise when they reach a certain age!!