Rear fog lights and tell tale light not working...

[ajt1503]

Hello
I would appreciate any ideas on the following problem.
I have a 1987 VW t25 which failed the mot due to no rear fog lights and no tell tale light.

So far we have:
We changed both the fog light and headlight switch for new ones.
We don't have any instrument lighting either so maybe this is tied up.
I have a test meter and have checked the continuity from the fuse to the switch (white & grey wire) and then from the switch to the rear light cluster. It's all good. Also, have checked the fuse and we are getting 12.77v supply so not quite sure where to go next.
We have removed the rear light cluster there is only one fog light bulb on the offside we have tested this and it has continuity.
Because there is no front fogs there is no relay in the fuse box.
A previous similar forum message said verify you have power going into the switch, can anyone confirm if you do this by putting one test meter probe on the positive terminal of the battery and the other probe across the switch??


I'm now going to trace and then check the continuity of the grey & yellow wire. This is a real head-scratcher! Any suggestions would be appreciated.

[Oldiebut goodie]

The power for fog light switches should come via a relay/or maybe direct from the headlight switch - a legal route so that they can't be put on on their own without headlights.
To test for power at the switch - red lead to the point you are testing and black lead to chassis/earth nearby.

[1664]

Because there is no front fogs there is no relay in the fuse box.
A previous similar forum message said verify you have power going into the switch, can anyone confirm if you do this by putting one test meter probe on the positive terminal of the battery and the other probe across the switch??

Does the indicator light on the fog light switch illuminated when the switch is in it's furthest position, i.e, rear fog ON? If so there is juice at the switch.



The relay has just been bypassed. Here's the Haynes diagram



Frankly I'd check the earthing at the rear light cluster since both the fog and side light are out. You can check there is +12v at the actual bulb holders with your meter positive probe and the negative probe touching a good sound earth on the engine block (with the appropriate switches on of course). Right, it's my birthday so I'm off out

[1664]

I've also just noticed that the fog and rear light share the same earth point which is just too coincidental in my mind.

[ajt1503]

The power for fog light switches should come via a relay/or maybe direct from the headlight switch - a legal route so that they can't be put on on their own without headlights.
To test for power at the switch - red lead to the point you are testing and black lead to chassis/earth nearby.

thank you both for the advice.

The tell tale light is not illuminated when the switch is put to the on position. This is a brand new switch from just kampers. We also put a new switch on for the headlights. The headlight switch is working fine and the lights go on/off. There is no tell tale light illuminating on the fog light switch.. oldiebut goodie. I read something earlier on the forum that said you only need a relay if you have front fogs, we havent got front fogs this ties in with the absence of the relay in the fuse box.

We will go try what you suggested about testing for power to the switch and see what happens. Many thanks!!!

[ajt1503]

The power for fog light switches should come via a relay/or maybe direct from the headlight switch - a legal route so that they can't be put on on their own without headlights.
To test for power at the switch - red lead to the point you are testing and black lead to chassis/earth nearby.

Oldiebutgoodie, we have power to the fog light switch... But the wiring diagram we have in our Haynes manual is a typical wiring diagram for front and rear fogs but we don't have front fogs.any others ideas... Do you think we should have a relay?The van passed the mot last year and nothing has been added or removed electrically from the van

[ajt1503]

Problem solved! We moved a relay from number five to number seven and the rear fog works. We just need a replacement for number five which is the heater. Can get mot done now