Help needed, weird problem with MK6 rear foglight.

[Adrian_Justice]

The rear fog light is permanently on and even stays on when I unplug the switch.

 

The light on the switch seems to illuminate for a while every now and again, it comes on all by itself and when on is unaffected by switching.

 

It started with the prolonged rain after Christmas and afraid I just removed the bulb. Forgot all about it until I went for the MOT today and it failed.

 

Any advice on how I might fix it would be appreciated.

[shawdreamer]

you maybe experiencing a common fault with the rear bootlid wiring that's caused by the wires feeding the rear fog and wiper deteriorating to a point were the cable coverings crack and comes away allowing lives and earth's to cross over to each other.

 

typically the deterioration occurs around the and inside the rubber tube duct at the top of the boot were the wiring passes from the bootlid into the main cabin roof space were the wiring is forced to flex when using the bootlid itself.

 

I had a similar issue with my rear fogs (On my previous Si Id made the second redundant light functional) which first manifested itself by occasionally making the fogs unusable until the bootlid was opened and the tube was given a shake, it later bizarrely developed another symptom were whenever the rear wiper was used the lights would dimly illuminate when the wiper arm was coming up the rear window.

 

It didn't go away till I took on the annoyingly fiddly task of stripping all the bootlids wiring out and replacing it with a good loom,

 

Id advise for the time being you pull the plug off the rear fogs bulb until you can figure out the cause to stop it coming on when not needed.... my local rozzers atleast love throwing about 60quid fines for that kinda thing.

[scottybo]

Could just wire in ur own switch if u cba for takin the boot apart. It would only take an hour or 2. Even if you redid it properly at a later daye. At least u wld get thru the mot

[Adrian_Justice]

Thanks for the help shawdreamer and scottybo. I guess you were right about a couple of wires lost their sheath and are making contact somewhere between the switch and the bulb.

 

Thought I'd report back in case it helps anyone in future, I tried cutting the positive to the fog light and connecting a cable to each side of the cut and running the two cables back to a new switch on the dash therefore allowing me to open & close the positive to the lamp, strangely this caused the once permanently on fog lamp to refuse to come on at all when switched!

The final solution was to take the positive input to the original switch, cut it and solder it to the new switch and the switched output directly to the live of the lamp, I found an old push button switch that had a coloured bit of plastic inside which mechanicly pops into a clear window on the top of the switch when pressed into the on position, RS components sell these and it saves the hassle of wiring up a seperate indicator lamp needed for the MOT.

 

Passed MOT today!