View Full Version : fog light wiring

17-02-04, 06:36 PM
I checked the fog lights today and found that it doesn't work. Quite bizarre really as i'll explain. The blue/red wire (feed) goes to a switch, then to a warning light then to the white/brown which goes to the fog light, as per pilgrim diagram, all clear so far? When i turn the fog light on (with the ign on and the lights) the warning light comes on but the Fog light doesn't. The bulb is ok. There is 12v at the bulb at the rear. Now it gets strange. If i take the bulb out or if i disconnect the wires at the bulb the warning light stays on so it's finding earth somewhere, PLUS if i put the main beam on, the fog warning light goes off!
I have a basic knowledge of electrics but the way i see it is there must be a short circuit between the warning light and the bulb??? Can anyone confirm this from the description I’ve just given? So, why would the warning light go off when the main beam goes on? I can't see from the wiring diagram how the two are connected. Has anyone come across this before? If so what’s wrong and how do i fix it?

17-02-04, 06:55 PM

I think you have a main fog bulb earth problem.

The feed for the power to the fog switch should be from the low beam headlight circuit - the fog light is only allowed to come on on low beam. When you switch to main beam it should go out. Go and try it on your daily runner, that's the way it's supposed to be.

The fact that your warning lamp goes out on main beam suggests the power feed is correct.

The warning light should also be earthed seperately to the main fog bulb otherwise if the warning lamp blows the fog light won't work. Your description suggests that is correct also.


Purple AK
17-02-04, 07:28 PM
I'm with Russ on this one, Check the earth on the rear fog light, also check any crimped connections inside the light unit, they are nomally machine made and sometimes the core of the wire breaks although the connection looks ok. Did you actually power up the bulb to check it?
Cheers :tu

17-02-04, 07:59 PM
I wired up the fog light to the reverse circuit so know that the light unit works ok, also wired the reverse light to the fog circuit and that does'nt work. i checked earth at the fog light to ground via a continuity tester and that seems to be ok. are you both convinced it's an earth problem rather than a feed problem? how can i check?

Thanks guys :tu

17-02-04, 09:35 PM
Just to clarify, feed comes from light relay, then goes to switch, to warning light carries on to light unit. the warning light is in line, no seperate earth. so if the warning light lights up there must be earth somewhere along the wire. even if i disconect the light unit completely so the feed wire is not connected to anything the warning lights still lights up so am i right in thinking that the feed to the light unit must be earting somewhere between the warning bulb and and the light unit?


18-02-04, 08:36 AM
sorry mate that won't work. I dont know why the relay feeds the switch for starters, but that aside, if you have 12V on the switch then you feed that through 2 bulbs your effectively putting 6V across each bulb. But lets say the warning lamp has a much higher resistance than the fog light bulb, (which it will have) then youll be dropping a larger voltage across the warning bulb, so it will light, and a much smaller voltage across the fog light, so chances are it wont be noticable that it is lite,

Keith S
18-02-04, 11:01 AM
If you are using the Europa switch you may find the attached useful.
I got it from Mike at Pilgrim,:tu :tu

18-02-04, 11:11 AM
As Philip says that won't work. What you need to have is the feed from the switch going to both the warning light and the fog light, i.e 1 connector out of the switch to 2 wires, one to the indicator light one to the fog light, then both earthed separately.

Kev :tu

18-02-04, 04:07 PM
Thanks Phill and Kev, absolutely correct, all sorted now

Cheers :tu :tu :tu