hi i have a premier wiring loom fitted to my robin hood with zetec engine im trying to wire up the oil warning light at the dash end i have two wires black and brown and green both connected together for the light i think i have to add a earth and at the sender end i have a green and brown
with it all connected the light is on but will not go out it could be a dodgy oil switch can any one tell me what happens withthe switch does it earth when in use the not earth when oil presser come in any help would be great cheers ian

It's usual for the oil light sender to be earthed until it sees pressure, then it becomes open circuit. Can you temp fit a gauge to check you have pressure or use a bike/foot pump to apply pressure to the switch to see if it's working?

Brown/Green should connect to the oil sender and the other end to the lamp. The other side of the lamp is black.

Without the engine running the lamp will be on and when the engine is running (if everything is ok) should go off.

The circuit earths through the sender.

So to check the wiring pull the wire off the sender and lamp should go out, touch it to earth it should come on, if that's ok you need to check the sender, it may be bust or could even have incorrect pressure rating i.e. its switching point is higher than the lowest oil pressure of your engine at tickover.

A few oil pressure switches work the opposite way that is N.O ie pressure switches the connection. These were mainly fitted to cars with electric fuel pumps including many 1980s Rovers and Landrovers.