Hi all ! I'm having problems with finding out which wires are positive and which are negative on my locust ! It has a Sierra wiring loom and I need to know which wires are positive going to the rear indicators ! The two wires on the passenger side are red and black which seems obvious but on the drivers side the wires are black and green . I've looked at various wiring diagrams but don't really understand them . I assume the red wire on the passenger side is positive but on the drivers side is it the black wire or green please ? Cheers - Nick

Usually black is always earth.

I would guess black is earth as it is there both sides. Why not use a multimeter and check for continuity from the black wire to the chassis / somewhere connected to the battery negative.

A small test light is easiest, connect the crocodile clip to earth and touch the wires with indicator switched on and see which wire lights up the test light.

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I would be tempted to say 'don't assume anything' if you weren't the one to put the loom in! Just because the original car was colour coded doesn't mean the builder didn't reuse a length of the wrong colour because that was all he had left.

Testing would be my first port of call.

Lol welcome to my world.

Currently stripping and replacing previous owner's wiring. Funny thing is it must have all been wired correctly at first (went through iva OK) but then the engine was swapped and I suspect that's when problems have crept in.

On Saturday I discovered that the fan isn't working because it's wired to my indicator stalk!

This also goes some way to explaining why indicators aren't working...

Not the end of the world but a drawn out process to trace and test the wiring. Continuity checking and a test bulb will help but if your problems run deeper you'll need to strip the wiring so that you can trace individual routes as colours may well change a number of times from a switch to the bulb/ancillary depending on what the builder had to hand.

Ford used brown as the negative on the Sierra loom.
The coloured wires you have may all be positive feeds to the side lights, indicators or brakes with the earthing done via the fitting itself. Best bet is to do a full check with a multi meter.

Get yourself a cheap polarity tester.....never trust cable colours !!

.......or try and make a cheap one......

https://m.youtube.com/watch?v=EoK2TrKmMeg

Thanks for all the help . I checked the wires with a multimeter and job successfully done