Rear Fogs not working

[cavalier1990]

So this got flagged up in last MOT so thought I'd have a look.

First thing I noticed was the switch felt a bit flaky, it would click in but on pressing it again it seemed to stick, plus the light wasn't coming on, so I thought ok I got spare switch I'l try that, no difference. There is a 12v supply on I think it is bottom right terminal of switch, if looking forward at switch.

So then on to the rear lights, I checked supply at cluster, only for rear lights, nothing at other pin for fogs. Same thing with spare switch the little light doesn't illuminate.

I had a look at your run through of the fuses Robsey and didn't really understand what the bridge wire is for, never touched it or anything looks out of place, fuse 9 - counting from top left to right, looks ok.

Anything else I can check, I'm assuming if there is power at the switch then the relay is ok but nothing passing switch so possibly switch again? Seems odd though.

Cheers
Andrew

[Robsey]

Daft question, but
Did you have the side lights on.?

Fogs only come on with the side lights on.

If you have checked the fuse, and you have the relay bypass wire fitted, then that end should be right.

At the rear,
I assume all other lights work, so we can rule out a bad earth.

It is quite a simple circuit.

Voltage in from side-light circuit to the relay.
Fuse is okay - try a new fuse just in case.
From fuse to X6 connector in passenger footwell,
Then wire from X6 to the rear light clusters.

Have you done any body repairs and cut a wire (near side sill).?

[cavalier1990]

Daft question, but
Did you have the side lights on.?

Fogs only come on with the side lights on.

If you have checked the fuse, and you have the relay bypass wire fitted, then that end should be right.

At the rear,
I assume all other lights work, so we can rule out a bad earth.

It is quite a simple circuit.

Voltage in from side-light circuit to the relay.
Fuse is okay - try a new fuse just in case.
From fuse to X6 connector in passenger footwell,
Then wire from X6 to the rear light clusters.

Have you done any body repairs and cut a wire (near side sill).?

I had the lights on when testing as I knew fogs only come on when sides/hlights are on.

No body repairs to near side sill or in about the big connector. Closest would be floor pan/support and that was a while back.

All other lights seem to be ok, including sides. If power is at switch that is the voltage from relay, so it must be after that. I can take a look at the x6 connector. If there was break in wire after that you should still see a voltage appear on the switch outlet wouldn't you, not sure what pin but will check wiring diagram.

What crossed my mind was the work I done for the reverse lights if you remember. Maybe something there but that was in about the other x5 connector.

[cavalier1990]

Further checked operation of switch, old switch between pin 3 and 4 doesn't make any difference to ohm reading only open circuit, spare switch it goes between continuity and about 100 ohms when pressing switch. Also tried other 10A fuse.

[cavalier1990]

So, I'm totally stumped now, that's 2 other switches I've tried, I've tested continuity to the fog lights themselves, then removed bulbs to prove it broke the circuit (tick), supply being fed to the switch when lights on, nothing seems to be going through switch, surely I can't have 2 spare faulty switches. Tested both assumed good switches between pin 2 and 3 and getting a circuit, pin 3 being the supply from relay, then open circuit when I cycle the switch (off). The original switch is goosed, it's just open circuit all the time, originally I thought that was the issue but it's something else.

I'm thinking by the colour of the wire on the bridge this is where the dayrime running relay would have been, so where does the fog lamp relay come in to this? From looking at the pin 3 this is coming from pin 30 of the fog lamp relay, but there's no power at it only at pin 4, which suggests the fog lamp relay aint working, does that sound right? I should have voltage at both pin 3 and 4. Currently only got it at pin 4.

[cavalier1990]

Ok so I've figured out where this screwed up, I'm thinking lets look at the list of fuses again on the other thread, looked at the fog light fuse being fuse 27, I'd been checking fuse 9 Duhhhhhh don't know where that happened, but I then checked the fuse 27 and guess what - no fuse - ffs!

Plugged in spare fuse and voila, we have fog lights! Pays to check the simple things first as they always say, although I was going down the wrong garden path thinking fuse was ok!

Why fuse 27 was missing well that's another story.

[Robsey]

I never thought to confirm you were looking at the correct fuse.

I simply expected it to be something more complicated

I just pulled up the fuse list...
Fuse 9 is instruments and number plate light.
Fuse 27 is for rear fogs.
Although fuse locations and functions did change dependent upon model year, and model configuration (trim, engine and optional extras fitted in the factory).

Ah well - another item ticked off from the pre-MOT repairs list.

[iangsi]

In my 1990 GSI only the drivers side one works, someone has run a cable from the live output of the switch to the rear & spliced it into the loom.

[ilovedmymantas]

Ok so I've figured out where this screwed up, I'm thinking lets look at the list of fuses again on the other thread, looked at the fog light fuse being fuse 27, I'd been checking fuse 9 Duhhhhhh don't know where that happened, but I then checked the fuse 27 and guess what - no fuse - ffs!

Plugged in spare fuse and voila, we have fog lights! Pays to check the simple things first as they always say, although I was going down the wrong garden path thinking fuse was ok!

Why fuse 27 was missing well that's another story.

I'm sure we've all done it, the fuse cover layout's not the clearest, more ikea than airfix

You've got me intrigued though, how did the fuse vanish? Let us know if you work it out.

-----------------------

In my 1990 GSI only the drivers side one works, someone has run a cable from the live output of the switch to the rear & spliced it into the loom.

Old-school 'get it through the mot at no cost' option, I must admit I'd have at least have tapped a wire across to the other light in the old days...

….ahh, simpler times

[cavalier1990]

In my 1990 GSI only the drivers side one works, someone has run a cable from the live output of the switch to the rear & spliced it into the loom.

Looking at the wiring diagram the feed to the lights splits into each light so both should come on, unless of course the splice is done beyond the wire split and is only onto one of the feed wires.

[cavalier1990]

I never thought to confirm you were looking at the correct fuse.

I simply expected it to be something more complicated

I just pulled up the fuse list...
Fuse 9 is instruments and number plate light.
Fuse 27 is for rear fogs.
Although fuse locations and functions did change dependent upon model year, and model configuration (trim, engine and optional extras fitted in the factory).

Ah well - another item ticked off from the pre-MOT repairs list.

It's ok because I didn't even question it at first so I thought the issue was after the fuse. It's only when I thought there is power to switch, power to fuse (the wrong fuse) and nothing is happening I decided to go back to basics!

[cavalier1990]

Ok so I've figured out where this screwed up, I'm thinking lets look at the list of fuses again on the other thread, looked at the fog light fuse being fuse 27, I'd been checking fuse 9 Duhhhhhh don't know where that happened, but I then checked the fuse 27 and guess what - no fuse - ffs!

Plugged in spare fuse and voila, we have fog lights! Pays to check the simple things first as they always say, although I was going down the wrong garden path thinking fuse was ok!

Why fuse 27 was missing well that's another story.

I'm sure we've all done it, the fuse cover layout's not the clearest, more ikea than airfix

You've got me intrigued though, how did the fuse vanish? Let us know if you work it out.

-----------------------

In my 1990 GSI only the drivers side one works, someone has run a cable from the live output of the switch to the rear & spliced it into the loom.

Old-school 'get it through the mot at no cost' option, I must admit I'd have at least have tapped a wire across to the other light in the old days...

….ahh, simpler times

I'd been mucking about with reverse lights and associated wiring about a year ago (although not so much about fuses then), and also the cig lighter fuse blew a couple times a while ago (think it had been shorting in the back of the ashtray on something) and I'd been playing about with fuses then, so probably at one point then it happened. If you take a fuse out and then are not sure where you pulled it out that's when the fun begins lol, especially if it's not sitting inbetween other fuses so you don't have a reference where it went!

[iangsi]

In my 1990 GSI only the drivers side one works, someone has run a cable from the live output of the switch to the rear & spliced it into the loom.

Looking at the wiring diagram the feed to the lights splits into each light so both should come on, unless of course the splice is done beyond the wire split and is only onto one of the feed wires.

Using that logic it should back feed & both should light up I need to look at it in more detail, but as said it passes the MOT so good enough.

[cavalier1990]

Theoretically it should although there may be issue with wiring where splice was put or a problem before this.