Urgent Wiring Problem

[Bludger]

I've just had to replace the rear fog light because the last one was full of rusted water and sludge and had stopped working.

I picked up a bog standard one from Halfords, and fitted it last night.

However, every time I switch the fog light on, it blows the fuse to the side lights. There is obviously a short somewhere, but cannot find it.

The other problem is that I have my MOT tomorrow, so have to try and sort it tonight.

As far as I can tell, the fog light wire connects to the side lights SUPPLY load and the GND, runs to a switch on the dash, then runs along the driver side to the light. When the light is disconnected and the switch and side lights on, my testers are saying there is 11 - 13 V running along the wires.

As soon as I connect it up, I get a spark and the fuse blows.

CAn anyone suggest where I might be going wrong? If the wires have rusted a bit at the ends, would that cause a short? I tagged some 8amp wire onto the ends to get the right length, so could this be the problem? Do I have to use 5amp?

What about increasing the size of the fuse?

Any ideas would be greatly received.

[Apache]

I had this a bit ago when I fitted twin foglamps. Do you have the little round switch to the right of the steering column with a small LED that lights when the lights are on?

If so, check that all three spade connectors are fitted securely, and in the right place as mine weren't! They fall off easy and someone must have replaced them in the wrong order when they put them back. Pressing the switch resulted in connecting +12v and earth together with the obvious result!

Pop the switch out and get a continuity meter on it. You can work out how the switch functions. Then check the three cables to it for +12v continuous (the feed), 0v (the earth). The other is the feed to the lights. Connect them back up to the switch in the right order and you should be away.

Sorry if this is 'teaching grandma to suck eggs BTW. HTH

[Sancho]

If so, check that all three spade connectors are fitted securely, and in the right place as mine weren't! They fall off easy and someone must have replaced them in the wrong order when they put them back. Pressing the switch resulted in connecting +12v and earth together with the obvious result!

I had that on my 2.4 too. Except they had bypassed all those boring fuses and relays so pressing the switch resulted in smoke billowing out of the dashboard and some very hurried battery disconnecting. I'm still too scared to use the foglight on my V6......

[MattF]

I had that on my 2.4 too. Except they had bypassed all those boring fuses and relays so pressing the switch resulted in smoke billowing out of the dashboard and some very hurried battery disconnecting.

I'm not alone then. Buggers did the exact same thing with mine. Straight to the battery with no fuse inline, then connected it wrong.

[Wild Thing]

I've just had to replace the rear fog light because the last one was full of rusted water and sludge and had stopped working.

I picked up a bog standard one from Halfords, and fitted it last night.

However, every time I switch the fog light on, it blows the fuse to the side lights. There is obviously a short somewhere, but cannot find it.

The other problem is that I have my MOT tomorrow, so have to try and sort it tonight.

As far as I can tell, the fog light wire connects to the side lights SUPPLY load and the GND, runs to a switch on the dash, then runs along the driver side to the light. When the light is disconnected and the switch and side lights on, my testers are saying there is 11 - 13 V running along the wires.

As soon as I connect it up, I get a spark and the fuse blows.

CAn anyone suggest where I might be going wrong? If the wires have rusted a bit at the ends, would that cause a short? I tagged some 8amp wire onto the ends to get the right length, so could this be the problem? Do I have to use 5amp?

What about increasing the size of the fuse?

Any ideas would be greatly received.

The way it normally works is, power from the sidelights runs to the fog light switch, then from the switch to the light, the earth for the light is usually to the bumper or body at the back of the car, some of them earth through the fixing bolt for the fog light.
If what you are saying that the live is ok to the light until you connect the light, then the fault is within the light.
Some fog lights have 2 wires + and - which is also earthed to the bolt fixing, so if you put the feed wire from the switch to the wrong wire it would create a dead short to earth via the bolt.
The best way to check all is ok is to put a bulb on the end of the wire from the switch, and touch the other terminal of the bulb to the bumper/body, it should light up without blowing the fuse.

[paulh]

The way it normally works is, power from the sidelights runs to the fog light switch, then from the switch to the light, the earth for the light is usually to the bumper or body at the back of the car, some of them earth through the fixing bolt for the fog light.
If what you are saying that the live is ok to the light until you connect the light, then the fault is within the light.
Some fog lights have 2 wires + and - which is also earthed to the bolt fixing, so if you put the feed wire from the switch to the wrong wire it would create a dead short to earth via the bolt.
The best way to check all is ok is to put a bulb on the end of the wire from the switch, and touch the other terminal of the bulb to the bumper/body, it should light up without blowing the fuse.

Spot on Gary

[Gizmo]

1st of all make sure you are connecting the spade connectors to the correct connectors. I found that when I replaced the fog light i had a lapse in concentration and had put the connectors on wrong way round