Relay Reconnection

[E-bmw]

Penelope Stopit said:

Sometimes a person will wire the switch to switch a negative to the relay

Correct, and don't forget that one, it is more common than you think but you will find that out when you start testing, hence why I said check switch in & out.

[Macski]

Again many thanks for your replies
.
Today took the switch out and found only two wires attached to the switch, a ground and a wire that becomes live when the headlights are switched on, I presume I am missing a feed to the relay.

Question do I really need a relay, would an in line fuse not be sufficient?

[Penelope Stopit]

In which case there is a very good chance that the side/head switch switches negatives

The relay has been fitted to send a positive down to the rear fog light

In summary........

Relay should have

Terminal 30 - Fused battery supply

Terminal 87 - Cable to rear fog lamp

Terminal 86 - Fused battery supply (Link it with short cable to Relay Terminal 30)

Terminal 85 - Switched negative from fog light switch

Other side of fog light switch should be connected to side/head switch that becomes negative when switching lights on

[Penelope Stopit]

There could be another option

Listen while you turn the sidelights on/off and you may well hear a tail lights relay clicking behind a kick panel where the fusebox and relays are located, the tail lights relay switches a positive down to the number plate lights and tail lights (first position of side/head switch)

You could pick-up the switched positive from the tail lights relay and wire it to a rear fog lamp switch, now you would be able to switch that positive down to the rear fog light

[Macski]

Thanks for everyones advice.

Fixed it yesterday, started tracing the wire from the fog light to the switch, The switch was disconnected from the fog light, the wire was 2ft to short to reach the light switch!

Looked up its MoT history, it failed its MoT for non operating fog light in 2009, wasn't MoTed 2013, 14 and 16

[Penelope Stopit]

Nicely found