I've had the car for it's 1st MOT in 3 years and it failed on the rear fog light not working and have spent days trying to figure it out.

 

I have tested the relay and it works fine.

 

Fuse is fine as is the bulb

 

Switch is fine, and linked out the 2 pins on the circuit board to make 100% sure

 

I get power to the fuse and relay, so guessing the switch completes the ground circuit rather than supplies power?

 

Now if I ground pin 1 on the relay the fog light comes on, should that be correct?

Also if remove the relay and I link pins 1 & 2 then 3 & 5 then put 12v to pin 1 it also turns on the fog light?

Under both circumstances the switch doesn't alter whether it's on or off.

 

I have a basic electrical understanding but it's getting beyond me at this point and need some guidance, any suggestions what to test?

Your car is a UK spec (from a previous post you made)? This is the FSM wiring diagram for the rear fog lamp:

 

el-60.pdf

 

Assuming it is good, does the tell-tail light (under the boost gauge) come on when you press the fog light switch?

yes I've looked at the drawings but I'm not great at reading them!! haha

 

No life from the telltale but it illuminates when I "force" the fog light on

Can you confirm that you have the headlights switched on?

yep headlights are on

I've updated the FSM wiring diagram to include the pin numbers on the relay.

 

el-60.pdf

 

I get power to the fuse and relay, so guessing the switch completes the ground circuit rather than supplies power? Correct, switched GND to pin 2.

 

Now if I ground pin 1 on the relay the fog light comes on, should that be correct? I assume you mean pin 2? If you ground pin 1 you will blow the fuse

as it is permanent +12v.

 

With the relay in place, if the rear fog light and the tell-tale light comes on by grounding pin 2 that shows relay is OK and that the "load" side of the circuit

is working. The fault is on the switched GND circuit from pin 2 back. E112/M59 to M14 diode pack and then back through the rear fog lamp switch and the

lighting switch (in the headlights on position).

 

hi thanks for the help, been working late nights so not got much of a chance to look at it lately.

Found there is a break in the ground wire running to pin 2 on the relay, going to splice in a new one when I get a chance