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MG MGB Technical - Electrical Issues - Driving me Mad

I have had my 1980 LE in storage for a while and I am trying to get her back into shape to hit the road. She is actually in pretty decent condition except for a a few wiring issues that has made me replace the main wiring harness. I still have the problems though. So here is what is still not working. Brake Lights, Heater Fan, Turn Signals, Wipers, and Dash Gauges, radiator fans. What does work are hazards, front head lights, and dash lights, fuel pump, and car starts and runs.

Any ideas? Any "silver bullets?"

Also, When you start the car. Does the Brake Warning Light in the center of the dash come on when the car is cranking?
Mike Howard

Did you change the fuse box? The contacts often corrode from behind causing multiple problems.
Steve Postins

Yes. I replaced the fuse box and fuses with new ones.
Mike Howard

Mike - Start looking at the bullet connectors. They all have to be clean, with no corroaion and the sleeve portion should not have any of the sleeve broken off. Once you have cleaned a connection, put a dab of dialectric grease in the sleeve, push the bullet in and then smear some of the grease around the end of the connector (where the wire enters) to keep out moisture. Also check ALL of the ground points associated with the components you say are not working correctly. The ground connections have to be clean, with no corosion around them to work properly. See my article on ground point preparation at: http://www.omgtr.ca/technical/General%20Technical/grounding.htm
I suspect that you have several marginal connections rather than one thing that is causing all of your problems. Good luck - Dave
David DuBois

Hello Mike,

I read you're message this morning and decided to have a look at the schematics. I just did and I think I found where you're problem is.

There is a white-green wire running from the ignition switch to a line fuse. After the line fuse this wire changes in a green-pink wire. This wire feeds most of the parts you name that do not work, the parts that do work are fed by another line.

First check the line fuse (I don't no where it is but in the schematic it's close to the wiper motor). Then check the Ignition switch and other contacts in this line.

Hope this helps you,

Siert
Siert Wieringa

Hi,

I had a look at my dad's car. The line fuse is close to the 4-way fuse box.

A 35A one is fitted there but I don't known if that is right value

Siert
Siert Wieringa

Hi All,

Thanks for your replys.

I think I'm running into a bigger issue.

When I turn the iginition key to the open position. Isn't there suposed to be power that goes through the other three fuses in the 4-way fuse box besides the one with the thick brown wires hooked up to it? I put my volt meter on these and get a big zero for current with the car in the on position for the rest of the fuses on the 4-way fuse box?

Shouldn't these have power since the switched power source is on? What could be preventing this?
Mike Howard

The top two fuses are fed by a common red feed from the light switch. Makes the park/tail/side work, one fuse for each side.
The #3 fuse is fed by a W/N from the IGN relay in front of the fuse box, controlled by the key. That is all the key on stuff, TS, Brake lights, wipers, gauges, heater.
If you replaced the harness, you should have a diagram, study it, learn it, follow it.
FRM
http://www.usachoice.net/gofanu
FR Millmore

Hi All,

Again, thank you for your responses.

I found the problem. Bad starter relay. I replaced the original Lucus relay with a Hella relay that I had in my garage. Everything works now.
Mike Howard

Mike,
That must have been the IGNITION relay in front of the fuse box, right? The START relay is behind the fuse box. It gets most confusing for all when folks use the wrong term for something, especially if the word used belongs to something else!
FRM
http://www.usachoice.net/gofanu
FR Millmore

This thread was discussed between 11/06/2004 and 15/06/2004

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