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Blink

Front Lights On When I Brake

27 posts in this topic

Hi sorry if this has been posted before, I think this may be a common problem according to search engine results, but fixing it is driving me mad!

Driving home I noticed in the reflection of the car in front when I applied the brakes, dim lights were coming on, now its a bit darker I can now also see the dashboard lights are coming on under braking too. When I turn my side or headlights on my brake lights are on permenantly....unless I open the tail gate then the problem goes away? My reg plate lights are now not working either, cant seem to see if they have a separate fuse?

Brake light bulbs look ok both doulble filament and it seems impossible to put them in the wrong way round.

Any help on this is greatly appreciated.

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Hi sorry if this has been posted before, I think this may be a common problem according to search engine results, but fixing it is driving me mad!

Driving home I noticed in the reflection of the car in front when I applied the brakes, dim lights were coming on, now its a bit darker I can now also see the dashboard lights are coming on under braking too. When I turn my side or headlights on my brake lights are on permenantly....unless I open the tail gate then the problem goes away? My reg plate lights are now not working either, cant seem to see if they have a separate fuse?

Brake light bulbs look ok both doulble filament and it seems impossible to put them in the wrong way round.

Any help on this is greatly appreciated.

i would put money on it being a bad earth connection somewhere

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i would put money on it being a bad earth connection somewhere

Thanks for the reply, any usual suspects (bad earth) to look out for?

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I would start with disconnecting the battery and cleaning the terminals along with the earth line that runs off the negative terminal onto the bodywork. This is quite a common "bad earth" point that can corrode and/or get badly contaminated.

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I would start with disconnecting the battery and cleaning the terminals along with the earth line that runs off the negative terminal onto the bodywork. This is quite a common "bad earth" point that can corrode and/or get badly contaminated.

Those look ok, checked fuses & bulbs, now when i brake rear side lights not brake lights are coming on, I hate electrics! What am I missing?

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Those look ok, checked fuses & bulbs, now when i brake rear side lights not brake lights are coming on, when I turn side\headlights on nothing is coming on at the rear, I hate electrical problems!

Found a severed wire, top right of enginge bay, disappears under the plastic whch covers wiper motors...I assume, anyway repaired it but has made no difference so not sure what that did?

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The bad earth (if it is that) will be at the point common to the brake / tail lights to cause this problem, i.e at the bulb socket. If its not a bad earth the next likely suspect is one of the rear brake / tail bulbs itself, the filaments may have shorted.

Take the bulbs out, one of them should be causing the additional lights to come on.

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Bit of an update..... Have replaced both stop\tail lights and licence plate light units which are still not working. Smoke has started to appear through the back of the steering wheel cowling! I turned car off, removed the lower plastic so I could see the pedals and wiring, the wires from the brake plunger (for want of a better term) become extremely hot when brake pedal is pressed (I know it is because there is current going through but seems excessive)I think it may be melting wires hence the smoke? now I dont know what to do.....

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Bit of an update..... Have replaced both stop\tail lights and licence plate light units which are still not working. Smoke has started to appear through the back of the steering wheel cowling! I turned car off, removed the lower plastic so I could see the pedals and wiring, the wires from the brake plunger (for want of a better term) become extremely hot when brake pedal is pressed (I know it is because there is current going through but seems excessive)I think it may be melting wires hence the smoke? now I dont know what to do.....

sounds like a short circuit in the system somewhere. it might be time to speak with a professional auto spark now before this gets very expensive or possibly causes a fire

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sounds like a short circuit in the system somewhere. it might be time to speak with a professional auto spark now before this gets very expensive or possibly causes a fire

You're right but funds is the problem....the car is not being used until sorted.

I feel the reg plate lights not working is no coincidence having fitted brand new ones today with no affect, will be tracing as much wiring as I can tomorrow. I just hope that the damage hasn't already been done. If anyone has any other input or ideas to check or try please post

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I would try to isolate which circuit the fault is on.

You could pull the brake light Fuse 54 in the central fuse box behind the glove box.

Then check if the other lights work.

If the fault is still there try putting this back in and pull the side lights Fuse 22 in the engine compartment box and try again.

Have you tried the high level brake light? try disconnecting this and see what happens.

I would have thought that as the brake light circuit is taking too much current Fuse 54 would have blown.

You might consider putting a lower rated fuse than the 15A in here until you find the fault.

I have an estate and there is a multi-block connector above the nearside rear wheel arch but I don't know where this is on the hatchback. This could have had water ingress.

Roger

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I would try to isolate which circuit the fault is on.

You could pull the brake light Fuse 54 in the central fuse box behind the glove box.

Then check if the other lights work.

If the fault is still there try putting this back in and pull the side lights Fuse 22 in the engine compartment box and try again.

Have you tried the high level brake light? try disconnecting this and see what happens.

I would have thought that as the brake light circuit is taking too much current Fuse 54 would have blown.

You might consider putting a lower rated fuse than the 15A in here until you find the fault.

I have an estate and there is a multi-block connector above the nearside rear wheel arch but I don't know where this is on the hatchback. This could have had water ingress.

Roger

Morning Roger

Thanks for post, I too have an estate......minus a lot of interior trim as I check the length of the car, will try your suggestions mate let you know how I get on.

When I bought the car the brake light fuse had blown, put another in and all seemed ok till now? Mechanics im fine but when it comes to electrics im a bit of a simpleton so fail to understand what the symptoms are telling me.

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On inspection of fuse 54 (Brakes) the plastic surround looks as though it has melted a little but for some reason the fuse has not blown? With the fuse removed turned on side lights still nothing at rear, fuses for these seem ok?

Also found fuse 32 (light switch) had a 20 amp instead of a 10 and this had blown, replaced but no difference.

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Sorry - where I got fuse 22 for the side lights I don't know!.

Fuse 47 [lhs] and Fuse 48 [rhs] in the central fuse box are the side light fuses.

These supply both back and front side lights so is it just the back ones not working?

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Sorry - where I got fuse 22 for the side lights I don't know!.

Fuse 47 [lhs] and Fuse 48 [rhs] in the central fuse box are the side light fuses.

These supply both back and front side lights so is it just the back ones not working?

Lol, did wonder about fuse 22, did work out the right ones though.

you're correct, front sidelight work, rears dont?

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I've just looked at mine - there are two multi-plugs behind the panel above the rear wheel arch.

The blue connector has an Orange and an Orange/white leads - these are the side lights.

Have you got a multimeter? Can you check if you are getting power on these?

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I've just looked at mine - there are two multi-plugs behind the panel above the rear wheel arch.

The blue connector has an Orange and an Orange/white leads - these are the side lights.

Have you got a multimeter? Can you check if you are getting power on these?

I havent mate, just switched hazards on to check, these do not work on rear either, so safe to assume I have nothing on working on the rear of the car?

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Not having a multimeter trying to trace electrical faults is a problem...

Alternatively, if you have a soldering iron you could solder a couple of wires onto a 12v bulb and use that for basic tests.

Connect one side to an earth point and carefully touch the other lead on the pins of the multi-plug and see what you get., make sure you don't short across the pins.

There is the possibility of course that the wiring loom is damaged before it gets as far as the plug but at least this will confirm this or not.

Failing that the only thing I can suggest now is to unplug both rear clusters and the high level brake light and plug them up one at a time and see if anything works.

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ok......

I made up a simple light bulb circuit as suggested, went to the multiplug at the rear, all dead.

I believe (please correct me if im wrong) these then connect through the car to another main plug at the front passenger footwell underneath some trim. At this point they are live. (Bulb lit up and flashed for hazards)

So I THINK the wiring loom is ok at least to here, and there is a break from the plug in the footwell to the plug at the rear of the car?

That make sense?

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Scrap that, multi plug in passenger foot well is fine, has to be screwed in to make connection......school boy error!!!!

Rear indicators and sidelights including reg lights are ok.

I havent attempted to insert another fuse into brake system yet.....

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Scrap that, multi plug in passenger foot well is fine, has to be screwed in to make connection......school boy error!!!!

Rear indicators and sidelights including reg lights are ok.

I havent attempted to insert another fuse into brake system yet.....

Good...at least you are getting somewhere!

So it is just the brake lights now? which brings us back to the clusters and the H/L brake light.

I would still say to unplug both rear clusters and the high level brake light and plug them up one at a time and see when the fault occurs.

Roger

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With all brake lights unplugged it blows fuses the second I touch the brake pedal. I removed the brake plunger mechanism and inserted a wire to both contacts to complete the circuit still blows so plunger itself is ok.......any ideas?

It also seems to have blown the light switch fuse again.

Edited by Blink

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If you undo the multi-plugs at the rear of the car does it still blow fuses?

If it does the fault is somewhere before them if it doesn't the fault is in the rear wiring somewhere.

Divide and conquer!!

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before I disconnected the rear multiplugs the wires leading into the light switch were very hot (too hot). I disconnected the blue plug fuse blew, reconnected and removed the grey plug, all ok with no heat in the light switch wiring, so problem is at rear of the car?

looking at the grey multiplug there is a green wire with yellow stripe, it appears to have fused itslef to a couple of other wires where it has touched them. Anyone know what this wire operates?

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I would say it definitely is.

The two normal brake lights go through C50 [the blue one] and the high level through C48 [the Gray one] I think.

Just to confirm this, when you disconnected the grey one do the cluster brake lights work OK?

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