General Wreg (2000) JTD S- weird lights fault-pls help

[Thomas P]

OK everyone..........Who knows the answer to this one........?

For no apparent reason this problem has started....Engine running, lights off - I depress the footbrake and the front sidelights illuminate and so do the instrument lights (as do the brake lights)

Engine running, lights on (sidelights or headlights makes no difference) - the brake lights are on all the time (when I depress the footbrake there is a slight change in intensity (v slightly brighter)

I have tried to identify the problem without success. I thought it may be the light switch on the steering column but when it is disconnected the front sidelights (and the brake lights) still illuminate when I depress the brake pedal.

I thought it might be the footbrake switch so I had a look to find there are two switches that operate when the brake pedal is depressed. There is also a third switch that operates in the same manner when the clutch pedal is depressed. I presume two of these are engine management features and one is the brake pedal switch but I am not sure.

The rest of the car is working perfecty in all respects.

Can anyone help with this?.....It may be a bad earth somewhere but I cannot find one, but then the car is in really good condition so it is a bit early for bad earths and such like.

I'm sure, though that someone will recognise this fault........Any help would be very gratefully received........(possibly one of the brake pedal switches gone faulty?)

I know this is a good forum so if you know my problem please say. I don't want to visit FIAT as they will just charge me a fortune for what must be a simple fault.

thx anyway

Tom

 

[Pat H]

Sounds to me like no earth on teh rear light asemblies.
When the brake light gets power it's uising the sidelight circuit to make ground.
Put a meter on the earth for the rear brake light and the bodywork. Get somebody to push the brake peddle and see if you get a volt rise. If you do try grounding it out and see if it comes good.
If it is ok then you need to trace back to where the rear assemblies get their grounding.

 

[Thomas P]

Pat H

Thanks very much for the knowledgeable and helpful reply. I appreciate it..............I have just spent another 1.5 hrs messing about with this problem to discover that I think I have a faulty stop/tail light bulb!!! Never heard of that before.....I did what you said and didn't really notice a difference (perhaps 0.1 volts - the meter couldn't really make up its mind). I examined the light fitment and could detect no problems either

I tried by substitution removing one bulb then the other but the suspect bulb was faulty when I tested it on both sides of the car and the non suspect bulb wasn't faulty. When all the bulbs are connected up and operating the fault is still there but when I remove tha suspect bulb the fault disappears immediately. Therefore would you agree that the bulb must be faulty?........or could it still be a dodgy earth that can't carry enough current for two bulbs?

The glass of the suspect bulb is more smoke burnt than the other and not too long ago I did replace both stop tail lights because one had blown.

I think it may be worth just adding another earth return to both rear lights.

I thank you again and would like your comments on the above.

Tom

 

[Pat H]

Well you can test the bulb with a wire sraight on the battery.
Strange for it to give that fault unless it internally has a broken earth.
For the cost of a new bulb (you should ahve a aspare anyway) I'd try that.
An extra earth shouldn't hurt anyway.

 

[Thomas P]

Thx again Pat H

I have just tested both bulbs with my tester....The dodgy one shows 0 resistance between the earth surround and the two lead connections at the base. Mind you the non suspect bulb only shows 1 ohm and 3 ohms resistance. I hope my assumptions are correct ..........

Your comments?

I used to love doing cars but I just find them annoying these days....

I will let you know
thx again
Tom

 

[Thomas P]

Pat Horridge

I love you and want to have your babies.....................(just joking, not really).

Everything now back to normal two replacement bulbs and everything now works A1.......I must say I have never heard of a faulty bulb like that....still I suppose you get what you pay for (Halfords.......bloated prices and crap quality)

Thx again and good luck.
Nice to see there are people out there who can help

Tom

 

[Pat H]

Well it is wierd to get a bulb with a fault like that. but as sherlock holmes used to say. When all the obvious things are eliminated even the what evers left, however starnage must be true.
"well maybe I paraphrased!"

 

[anh167]

Hi, just browsing through the different threads posted, and I had an electrical fault at the rear of my wifes:worship: Ulysse, and it may be worth while you checking to see it the fault is the same with yours.

If you open up the tailgate, at the top near the hinges, you will see rubber channelling that the different wiring passes through for things like central locking, lights and the wiper etc. After a period of time the wires can become brittle and snap, as was the case with the earth, and a wire for the n/s fog light and wiper relay feed. This lead to 'pretty' light shows and a lot of head-scatching, but once I repaired the wires, problems seemed to be sorted out.

Hoping you have some joy rectifying yours