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MG MGA - Wiring Harness Grounding Points

I'd be grateful for an answer from someone who has installed a wiring harness. Simple question - are the various grounding points which spur out of the harness at various positions, as well described by Barney, all interconnected between the separate pieces of harness, or do they just each ground a group of electrical components supplied with power by that portion of harness?
Bruce
B Mayo

Three grounding points are all independent, not interconnected. One is on the firewall near the fuse block, screw through the bulkhead with hex nut. One is in RF corner, originally on the second fender bolt (extra length) up from the air pan with a hex nut. The third is near RR corner on a tab under the frame very near the fuel tank sender unit. Disconnect the bulkhead ground and stuff on the dash may not work, as well as the charging system, heater and wipers. Disconnect the front ground and the front lights and horn fail. Disconnect the rear ground and the rear lights fail.

There are a few things independently grounded on the chassis. The fuel sender unit grounds on the tank which (originally) grounds through the steel fuel line to the fuel pump which has a ground wire to the frame. engine starter motor and distributor ground through a heavy cable to frame, originally across the left motor mount.

On the dash, the turn signal warning lamp and map lamp ground on the steel dash panel. Instrument lamps originally ground on the instruments (which in turn ground through the harness). Some recent replacement harnesses substitute bayonet base bulb sockets, each having a ground wire that must be connected to the dash hardware.
Barney Gaylord

I think I'm right in saying there a 4 proper earthing points. One on the screw that holds the flasher unit, that's the main earth for the regulator and windscreen wipers. An earth for the front lights which uses one of the wing bolts. There another earth for the instrument panel but I can't remember where that is earthed without looking. The fourth is for the rear lights and that is picked up from one of your cable fixing lugs. If you have a heater fan there is a fifth earth but I don't know where that comes from as I haven't got one. When I fitted my new harness it was pretty straight forward when you layed it out on the car and looked at the diagram, because it was exactly as the diagram is drawn. I did have to "buzz" some of the same colour wires out that go behind the dash, red ones I think they were, as you can't see where the go once they dissappear into the form.
Lindsay Sampford

Wiper motor grounds at the control box, which in turn grounds at the bulkhead. Heater motor and dash ground wires all go to the bulkhead screw. Only one grounding point for everything in the middle of the car.
Barney Gaylord

All is clear. Many thanks Barney.
Bruce
B Mayo

This thread was discussed on 23/05/2009

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