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MG MGB Technical - Wiring help behind radio panel

I've got a 1973 MGB. My cigar lighter and courtesy light do not work. I tested the courtesy light on a battery and know it works ok. There are several wires hanging loose from the wiring harness, especially near the top of the harness. Can someone please tell me how each of the wires hooks up. I looked at the Haynes diagram, but am afraid I don't quite understand it. Also, what is the canister shaped metal object that is attached to the screw that holds the wiring harness clamp? It has three wires connected to it by spade connectors.

Thanks in advance.
JG Bowman

The best bet is to spend a bit of time looking at Pauls site, he has the diagrams in a nice easy format, then you can tie them up with the Haynes. The metal canister is probably either a nuclear firing pin, or the indicator flasher relay.
Try http://www.mgb-stuff.org.uk/
Tatty

Thanks for the help. This BBS is invaluable.
JG Bowman

Ok Tatty, I looked at Paul's site and it is helpful. However, I did not see diagrams dealing with some of the wiring that I have. If anyone could tell me how theirs is wired it would be much appreciated.
Specifically, I have a red/white double wire with a spade connector hanging loose at the bottom of the harness and two purple wires unconnected near the top in behind the radio. Finally, as I recall there is a disconnected double green/white wire.
JG Bowman

The two purple wires connect to the courtesy light. There should also be a black ground. I think the red/white goes to the rearwindow defogger if you have one. Purple wires and brown wires are always hot. Red wires and white wires are hot with ignition on. The Haynes manual diagrams this very well. You may have to get used to how its layed out. Use the "key" to find the item you want then track wires from the item like the courtesy light, to its source and wherever else it connects to. ItTs normally recommended you take it to Kinko's or similar and have it blown up larger then laminated so you can write on it to track wires.
william fox

So the purple/white wire on the back of the courtesy light does not connect to another purple/white wire?
JG Bowman

Let me check the book real quick.....Ok the purple wire is the main power coming in. The purple/white wires go to the door switches which ground the circuit and make it work. Black wire to the light grounds when the switch on the light itself is used.
william fox

The purple wires are the power supply (fused) to the courtesy light and cigar lighter. The door switch put a ground on the purple/white to light the courtesy light, loose wires come from each side into a double connector by the bracing strut behind the dash which is where the two loose wires come together, and also to another purple/white that goes into the loom for a few inches and out to the light. The red/white is the illumination for the cigar lighter which comes on with the side-lights. White/green is for a radio and carries power when the ignition switch is in the 'auxiliary' and 'run' positions.
Paul Hunt

Thanks, Paul. That tells me I have everything hooked up correctly. I checked the fuses and cleaned up the connections to the fuse box, but my cigar lighter and courtesy light still don't work. The only connection I haven't checked is the door switches, but I thought that even if they are unhooked that the light would work on the switched position. Additionally, that wouldn't explain the lighter.
JG Bowman

JG

The canister behind the radio panel is probably the flasher unit for the 4 way hazard flasher. The flasher for the turn signals is behing the glove box.

Jim
74B Roadster
James Conner

I have a 67, what are cigar lighters and courtesy lights????
Bud G

JG - you need to put a voltmeter or test-lamp on the purple at, say, the cigar lighter and check that you have 12v both with the lighter out and pushed in. Both the lighter and light need ground wires as they are mounted on the plastic console. If you have 12v on the purple check on the black with the lighter pushed in. If you see 12v here as well then the ground is bad. You can do the same thing on the coiurtesy light using the manual switch on its top. Only bother about the door switches when you have the manual switch working.

Your OO (original owner) must have been a cheap-skate, Bud, they were optional on the 67.
Paul Hunt

JG, If you haven't already done so, follow the electrical help link on the site. Rick has done a super job of breaking down and explaining the electrical system. and all of the diagrams are in colour. I have printed the whole thing and keep in in the workshop right next the the Haynes book. Between them I have been able to get a pretty good understanding of the Lucas mind.
Bob Anderson

This thread was discussed between 06/06/2002 and 08/06/2002

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