Brake Lights, but not as we know them.
Discussion
Hi
Having recently bought my Chim I have been over the moon with it, until this afternoon.
Soon after taking delivery I noticed pressing the brake pedal would illuminate the dashboard dials, however the brake lights still seemed to work fine so I put this down to some quirk or other and promised myself I'd look into it soon. This afternoon I realised these were not my brake lights at all but are, in fact, the rear side lights. It appears pressing the brake has the same effect as turning the light switch to the first 'on' position: the dash dials light up and the front and rear side lights come on. The only difference is that the brake switch's power source is ignition switched also.
Since I cannot drive the car at night (lights on = no brake lights), and in the day I will be flashing my front lights every time I hit the brake, the car is now off the road.
Does anyone have any idea what may have happened here? Some incorrect rewiring or other at a service/repair?
As far as I know the car electronics are standard, except for a fan override switch that has been fitted on the steering column. The car is a '99 500.
Looking at the wiring of the brake pedal, the wires from the switch come together with another from the bulkhead and another that dissapears into the side body work through a big lug hole. This loom then heads up behind the dash.
Any help would be greatly appreciated!!
Thanks,
Winters.
Having recently bought my Chim I have been over the moon with it, until this afternoon.
Soon after taking delivery I noticed pressing the brake pedal would illuminate the dashboard dials, however the brake lights still seemed to work fine so I put this down to some quirk or other and promised myself I'd look into it soon. This afternoon I realised these were not my brake lights at all but are, in fact, the rear side lights. It appears pressing the brake has the same effect as turning the light switch to the first 'on' position: the dash dials light up and the front and rear side lights come on. The only difference is that the brake switch's power source is ignition switched also.
Since I cannot drive the car at night (lights on = no brake lights), and in the day I will be flashing my front lights every time I hit the brake, the car is now off the road.
Does anyone have any idea what may have happened here? Some incorrect rewiring or other at a service/repair?
As far as I know the car electronics are standard, except for a fan override switch that has been fitted on the steering column. The car is a '99 500.
Looking at the wiring of the brake pedal, the wires from the switch come together with another from the bulkhead and another that dissapears into the side body work through a big lug hole. This loom then heads up behind the dash.
Any help would be greatly appreciated!!
Thanks,
Winters.
Two of the most common faults with brake/side lights are:
1) Putting a single filament bulb in a twin filament hole. (The brake signal will run back down the sidelight circuit illuminating the dash)
2) Bad earth. (Brake signal can't find the normal earth so earths down the sidelight circuit instead). Your brake lights and side lights would illuminate faintly at the same time. (Hard to see in a twin filament setup)
HTH,
John.
1) Putting a single filament bulb in a twin filament hole. (The brake signal will run back down the sidelight circuit illuminating the dash)
2) Bad earth. (Brake signal can't find the normal earth so earths down the sidelight circuit instead). Your brake lights and side lights would illuminate faintly at the same time. (Hard to see in a twin filament setup)
HTH,
John.
Edited by jhfozzy on Sunday 3rd August 21:45
The only common place I know off for both circuits is the rear lights themselves. I would check you have the correct filaments fitted, they should be dual 5/21w units (two coils inside) with two pins on the end cap, which can be easily forced in the wrong way round too. Then check you have a good earth return path back as both circuits share this through the casing, you may find it is getting an earth back through the side lights.
Hope this helps,
Cheers
Andy
Hope this helps,
Cheers
Andy
jhfozzy said:
Two of the most common faults with brake/side lights are:
1) Putting a single filament bulb in a twin filament hole. (The brake signal will run back down the sidelight circuit illuminating the dash)
2) Bad earth. (Brake signal can't find the normal earth so earths down the sidelight circuit instead). Your brake lights and side lights would illuminate faintly at the same time. (Hard to see in a twin filament setup)
HTH,
John.
Doh! 1) Putting a single filament bulb in a twin filament hole. (The brake signal will run back down the sidelight circuit illuminating the dash)
2) Bad earth. (Brake signal can't find the normal earth so earths down the sidelight circuit instead). Your brake lights and side lights would illuminate faintly at the same time. (Hard to see in a twin filament setup)
HTH,
John.
Edited by jhfozzy on Sunday 3rd August 21:45
Excellent. Back in business!
I looked at both bulbs and realised they looked very similar but not identical. By process of elimination I found the bad one, and replaced it with one identical to the good'n which I found in the previous owner's spares set. Put that in and it was back to normal.
The duff is marked 12V21/5W (B13)299BAY150. Any idea if this is the wrong one/for something else, or is the bulb just knackered?
Thanks John, Ian and Andy.
Had worried it was something more sinister, so will sleep a little easier now!
Cheers.
I looked at both bulbs and realised they looked very similar but not identical. By process of elimination I found the bad one, and replaced it with one identical to the good'n which I found in the previous owner's spares set. Put that in and it was back to normal.
The duff is marked 12V21/5W (B13)299BAY150. Any idea if this is the wrong one/for something else, or is the bulb just knackered?
Thanks John, Ian and Andy.
Had worried it was something more sinister, so will sleep a little easier now!
Cheers.
jhfozzy said:
Two of the most common faults with brake/side lights are:
1) Putting a single filament bulb in a twin filament hole. (The brake signal will run back down the sidelight circuit illuminating the dash)
2) Bad earth. (Brake signal can't find the normal earth so earths down the sidelight circuit instead). Your brake lights and side lights would illuminate faintly at the same time. (Hard to see in a twin filament setup)
HTH,
John.
Excellent advice... think this should go on the FAQ section....1) Putting a single filament bulb in a twin filament hole. (The brake signal will run back down the sidelight circuit illuminating the dash)
2) Bad earth. (Brake signal can't find the normal earth so earths down the sidelight circuit instead). Your brake lights and side lights would illuminate faintly at the same time. (Hard to see in a twin filament setup)
HTH,
John.
Edited by jhfozzy on Sunday 3rd August 21:45
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