Electrical fault - stumped

[gmdh555]

Hi,

 

I still can't get to the bottom of my fuse problem (discussed here)

 

To date, I have...

 

...opened up the brake and reverse light enclosures and checked for damp etc - the condition of them is excellent, but I still added some insulation tape over the screws holding the reversing light to the body;

 

...opened up the pedal box and checked for interference between the clutch pedal pin and the brakelight switch;

 

...checked the wiring to the terminals of the reverse light switch - no damage is apparent and there is already some foam padding stuffed in between the terminals and the transmission tunnel;

 

...tried a higher rated fuse.

 

At this point I've run out of ideas - changing the bulbs was suggested but I'm not sure this would be any use. I haven't changed any bulbs since I got the car, but this problem has only recently started occurring.

 

Any further advice gratefully received - my blatting is being restricted and the sun came out again today ☹️

 

Cheers,

Gareth

 

Yellow and black 1.8 VX, pics here

 

[F355GTS]

Gareth

 

On Robmar's car it was simply a badly seated bulb causing a short in the reversing lamp

 

Mark

[Nigel Riches]

First off DON'T INCREASE THE FUSE RATING, if it's the correct one for the application, more serious and permanent damage may occur.

 

Have you checked to see if the wiring is in good order where it passes through any of the panels?, all the grommets are in place and not split or missing, are there any pinched wires caught under washers or similar?, the lens mounting screws are not biting into the wiring in the light clusters?,

 

It could be one of lots of things, it will be hard to find and really only quite minor in nature, but don't increase the fuse capacity, fuses are cheap, easy to replace, car wiring loom fires are not funny, sorry for the heavy stuff, stick with it you'll crack it, Nigel.

 

1982. 5 speed, clamshells. B.R.G / Ali. The True Colours.

[Mike Molloy]

Intermittent problems are always annoying, but as with all things electrical it's easy if you apply logic. The old Sherlock Holmes quote applies - "eliminate the impossible, and whatever remains no matter how improbable must be the truth".

 

So - some questions:

1) Do you have a wiring diagram for your car, can you read it and are you adept with a DVM?

2) The fault is only that F1 (Brakes/Reverse Lamp 10A) blows?

3) The fuse blows at random intervals i.e. not immediately you brake or select reverse?

 

Assuming the wiring loom is similar to the standard K-series, then F1 is supplied by unfused Ignition power (white wire). From the other side of the fuse comes a Green wire that goes forward through the tunnel to the brake light switch in the pedal box. This wire is commoned at the switch connector and another green wire goes back to the reverse light switch on the side of the gearbox. If point 3) above is correct, then the problem is most likely to be caused by one of these two wires having chafed so it is intermittently touching the chassis. Obvious problem areas are where the main harness bundle goes through the tunnel top, and where the brake switch wires come through the side of the pedal box into the footwell. If you have missing or worn grommets it's easy for the wire insulation to wear through and short on the ally panels. You'll need to get under the car to have a look at the wiring in the tunnel. Make sure it's not flapping around.

If you have a DVM, remove F1, disconnect the green wires from the brake light and reverse switches and connect your meter (on ohms) between the green wires and a good chassis earth point. Then waggle the harness around and see if you can get the short to appear.

Tell me how you get on.

[gmdh555]

Thanks for the comprehensive responses - I really appreciate your time

 

Crossed fingers all round, but hopefully it's sorted. I went over the car again last night looking for chafed wires etc. I messed with a couple of things, one of which seems to have done the trick.

 

Firstly, the reversing light bulb didn't look particularly secure - that's a dodgy bulb holder if ever I saw one! Anyway, I reseated the bulb and also bent the terminal "spring" in a bit to hold it more tightly against the bulb.

 

Secondly, I found a wire with a bare connector floating around in the passenger footwell. It looks like it's been disconnected at some point and just wrapped around some other wire to keep it out of the way. I have a vague recollection that this was originally hanging from under the dash, and that I tidied it away out of sight behind the trim a while back. Anyway, potentially in that position it was catching the ali panel.

 

Frustratingly I don't know which of these was the culprit. Even so, after a hard blat last night and a commute to work this morning the brakelights are still working - halleluyah

 

Thanks again for all your help,

Gareth

 

 

Yellow and black 1.8 VX, pics here

 

[Mike Molloy]

Is the dangling connector connected to F1? If not, you haven't cured the problem. Sorry, but crossing your fingers isn't going to do it... ☹️

[Phil]

I FEEL THE PROBLEM WITH MOST ELECTRICAL PROBLEMS ON CARS IS A BAD CHOICE OF EARTH POINT OR A DRY CONNECTION,

DRY CONNECTION MEANS THAT EVEN THOUGH THE CONNECTION IS TIGHT IT MAY NOT BE A GOOD CONDUCTOR, SIMPLYB SAND DOWN THE CONNECTIONS AND RELOCATE IF NEEDED.

MY RECENT PROBLEM WITH REAR LIGHT AND THE FOG NOT WORKING WAS DOWN TO A BAD CHOICE BY THE BUILDER EARTHING ON A BOLT GOING THROUGH THE ALLY BODY WORK, NOW ON THE CHASSIS AND IS PERFECT.

BATTERIES AS WELL SUFFER BECAUSE THE SMALL CHARGE BACK FROM THE ALTERNATOR IS LOST BY THE OXIDATION ON THE LEAD TERMINALS , CAR STARTS OK AS LARGE AMOUNT OF POWER GOING ACCROSS TERMINAL BUT YOU END UP WITH A FLAT BATTERY.

 

X/FLOW 1700 DD 1990

ROAD USE ONLY..SO FAR