Front fog lights

Captain Jack · Post by **Captain Jack** » Tue Mar 27, 2007 9:33 pm

jameslxdt wrote:i could have sworn theres a relay for the fog lights, have you checked the bulbs?

Yeah the bulbs LOOK ok. Gonna have to see whether there's any activity around the fog light fuses - once I find my bloody multimeter!

Captain Jack · Post by **Captain Jack** » Sat Mar 31, 2007 4:55 pm

Welp, I checked for current in the fuses and there's nothing there. I can't find anything in the Haynes manual as to the location of the relay.... Can anyone help me locate it?

mjb · Post by **mjb** » Sat Mar 31, 2007 7:03 pm

If they aren't on, there won't be any current! Try checking the voltage across the pins of the light connector with them turned on

Looking in the Haynes there's no need to check the fuses because the 3 the fog lamps rely on all run a load of other stuff as well (note each lamp is run off a different fuse)

Going by the EPC, the relay will be one of three identical black relays that are on a raised area in the corner of the pile of relays by the drivers right knee. Part number "6555 HJ". The three are for "Turning motor", "front fog lights" and "daylight running lights" so i'd suggest yanking them one at a time until you get the right one, then check the voltage coming in on pin 1B which should be at around 12V while the foglamp switch is on.

Captain Jack · Post by **Captain Jack** » Sat Mar 31, 2007 7:12 pm

mjb wrote:If they aren't on, there won't be any current! Try checking the voltage across the pins of the light connector with them turned on.

Yes, of course they were switched on. I am not that much of a muppet

I tested my theory with the main beam lights, which are fuses next to the front fog ones and I am getting 12v on those with them switched on, but nothing on foggies ones. I'll check the voltages on the relay pins see if I am getting any activity on those.

mjb · Post by **mjb** » Sat Mar 31, 2007 8:49 pm

Captain Jack wrote:
mjb wrote:If they aren't on, there won't be any current! Try checking the voltage across the pins of the light connector with them turned on.
Yes, of course they were switched on. I am not that much of a muppet

I meant if the lights weren't lit, there'd have to be no current! If there were current in the circuit with the bulbs unlit, it would indicate a short circuit which would mean that by inserting the ammeter across what would certainly be a blown fuse, completing the circuit, you'd be creating a fire hazard and/or blowing the main 50A fuse F3 which runs a good proportion of the car...

I=V/R

Current (amps) = Potential difference(volts) divided by Resistance (ohms)

So you get 12v divided by resistance in a foglamp circuit with a short (ie. very low resistance, way under 1 ohm) means an extremely high current, which makes things smell and go bang/ignite

Methinks you may be confusing current with potential difference (a.k.a. voltage)

I tested my theory with the main beam lights, which are fuses next to the front fog ones and I am getting 12v on those with them switched on, but nothing on foggies ones. I'll check the voltages on the relay pins see if I am getting any activity on those.

OK Back to basics question. What exactly are you putting the voltmeter/multimeter probes on? If you're measuring between the 2 pins of the fuse socket, it'll only register a voltage of around 12v if it's working or if the circuit between the fuse and the bulb is shorting to earth. Not good. You need to test that there's continuity between ground and the lamp side of the fuse, and that there's 12v ish between the relay side of the fuse and ground. Chances are the ground continuity will be there but the 12v won't be, in which case I'd try replacing the relay with one of the others that are the same.

Captain Jack · Post by **Captain Jack** » Sun Apr 01, 2007 2:07 pm

Sorry, I should have been a bit clearer. I have been measuring voltages rather than currents (makes more sense). I have put the positive terminal on the fuse itself (the bit where you see whether it's blown or not) and the negative one of the body of the car. Obviously with the lights on, the voltage would flow over the fuse (pushed by current

), which is where I can measure it to see whether there's anything there. Since there was nothing there, I would assume either I fit the wrong type of relay or there's some other problem...

It's pretty sunny outside now, so I am gonna go crawl around some more and see what else I can find/blow up.

Captain Jack · Post by **Captain Jack** » Sun Apr 01, 2007 2:47 pm

OK just been under there and I am even more confused. I have checked the voltages across the pins and two of them are permanently on, regardless of whether the front fog light switch is in on or off position. One of them is the ground, and the other one is completely dead - I am assuming this one to be the one that takes the 12v feed from either one of the 12v sources and feed it to the lights. I would assume, that one of the 12v feeds would be off depending on whether the stalk switch is on or off, but they both remain on

I wanted to test whether the lights work at all by feeding the 12v into the 'dead' pin, but kind of chickened out in case it's something else (and I left my Haynes at home).... er.... any ideas?

And this is the relay I am using in that brown socket

jameslxdt · Post by **jameslxdt** » Sun Apr 01, 2007 3:10 pm

thats a 5 pin relay, it wont work, i did say to use a 4 pin relay

Captain Jack · Post by **Captain Jack** » Sun Apr 01, 2007 3:18 pm

Blah... OK

jameslxdt · Post by **jameslxdt** » Sun Apr 01, 2007 3:22 pm

make sure you fit the relay the right way round when you get the right one

Captain Jack · Post by **Captain Jack** » Sun Apr 01, 2007 3:25 pm

Well, I think that you can only fit it one way as one of the pins is positioned 90 degrees from the other 3

jameslxdt · Post by **jameslxdt** » Sun Apr 01, 2007 4:10 pm

ooops yes, very true

Captain Jack · Post by **Captain Jack** » Tue Apr 03, 2007 7:53 pm

Welp, bought a 4 pin relay and .... nothing

I stupidly left my multimeter at my folks place so I won't be able to measure anything for a few weeks. What type of relay do I need for this? This is one is a normally open type, which sounds like what I need....

jameslxdt · Post by **jameslxdt** » Tue Apr 03, 2007 7:55 pm

thats the correct relay, you need the meter and a haynes manual to check the connections from start to finish ideally

Benner · Post by **Benner** » Tue Apr 03, 2007 7:57 pm

Ok I was thinking about upgrading to front fogs, but after all the prob's Captain Jack has had fu*k that!!!