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MG MGB Technical - Electrical Fault

Lost wipers, turn signals, tail lights, temp, tach, fuel. Was doing just fine, been out on a damp day, started the car and let it run, shut it off and restarted several times in a short period of time. Checked fuses, they look ok. Don't see any lose wiring, at first glance.
What gives?
THANKS!
Mike
Mike

Cars as old as ours often build up corrosion. With the battery disconnected, wire brush the fuse holders and clean the spade push-on terminals as best you can. (I have a small points file that just fits). Some tuner-spray will help. You could also have corrosion in some of the connectors. Most of them are just ahead of the firewall on the right-hand side. You can clean these up to make better connections, although new connectors are often cheap insurance.

If some connections are going bad, it is likely that others will also. There's also a cluster of them in the trunk, right side.
Dan

Mike - Check those fuses with an ohmmeter or by replacing them. Fuses can look good and still be bad. Good luck - Dave
David DuBois

Mike,
All your inoperative components are on the same fused circuit, the 3rd fuse down from the top. If the fuse is good, then the current is not getting through. I suspect the terminals on the fuse block are corroded. You may be able to clean them up, but a new one is cheap and will save you hours of chasing electrical gremlins.
Regards,
Gary
Gary Wiggins

Mike,
Sounds to me like your fuse box needs a good cleaning. I like using a fine wire wheel, but househould ammonia willalso work well. Make sure when you reinstall the box that the connected fuses are upper most (you can put the box box on upside down.

Dave
David Kalp

Let the car sit over night and dry out. Pulled the fuse this morning all looked clean and making good contact. Put the fuse in, checked and have electrics again.
Mike
Mike Razor

To state the obvious, it sounds like you had enough surface corrosion between fuse and holder that it finally lost conductivity. Then, removing the fuse to check it disturbed the surface glaze enough to get your electrics back. I'd go back and clean the fuse and holder with a small wire brush or scotch brite pad to hold off future problems.

Best, Joe
Joe Ullman

And, to amplify on Joe's and Dave's good advice for fuses also know that the internal connections for the runners in the fuse block are all riveted and equally subject to corrosion. If your fuse block looks original and pretty sad from a corrosion standpoint, it might be cheap insurance to replace it.

If you choose to do that, remove the battery ground strap, and then move each wire from the old to the new fuse block one at a time to avoid confusion. Also, before you make the wire exchange, it is smart to get some silver bearing solder or rosin core solder and apply solder to the rivet connections on the backside of the new fuse block. This will not only ensure a good electrical connection but prevent corrosion at those points in the future. If you want to really ensure that it is well protected back there, simply "pot" all the soldered runners/rivets with some silicone seal. Once all that is done, it should last you a very long time without hassles.

The wiring connections can be protected with something like vaseline or silicone grease, as well as the clips for the fuses.

Good luck!
Bob Muenchausen

Mike,
One thing I do know. Electrical problems on old British cars do not fix themselves. They only hide so they can resurface later. Usually late at night, far from home, during a thunderstorm, when all your friends are out of town. And next time it may be the fuel pump that stops working. Do yourself a huge favor and fix that fuse box.
Good luck,
Gary
Gary Wiggins

the fuse box and ancillary (sic) wiring appears to be in good shape. It was raining quite a bit when I had the car out. I wonder if dampness could have caused the problem somewhere in the wiring harness?
This fuse box has a plastic cover over it and it took a few minutes to find the fuses. I guessing that this was on a new MGB.
Mike
Mike Razor

All those circuits are powered from the 2nd fuse up. Put a test lamp or voltmeter on both sides of that fuse, and the spades on both sides, and check for 12v with the ignition on. Late 70s cars got an ignition relay (brown/white wires on the fusebox instead of white) so if you have no 12v anywhere on the 2nd fuse it could be that. It should click when you turn on the ignition.
Paul Hunt

I have a similar problem. I have no clock, radio, horn, or map light. I cleaned the fuse box and checked for loose connections, but still nothing. Is this an issue of a bad ground?


Adam
A.M. Keller

I also had a similar problem and found the tacho,fuel etc was off one earth which can be located on the cigar lighter it then splits off to several devices.Mine had come adrift giving strange results.
All electrical circuits will naturally try and find ground.check your lights again you may find a very faint glow which truly indicates an earth problem.
richard gallagher

Clock (late car?), horn and map light (early car?) are on the bottom fuse (purple circuit, always hot). Courtesy lights are also on this circuit.

The radio should really be on the accessories position of the ignition switch (white/fgreen), if you have one, in which case it should also have its own in-line fuse behind the radio.
Paul Hunt

Unfortuantley I am waiting until next weekend to look into this further, but thanks for all the info. I'll be sure to post my victory on the BBS. I also should have mentioned that it is a 79 B.

Adam
A.M. Keller

By the way. For those of you that say electrical faults don't fix themselves.....

Had a '71 B one night a righteous amount of smoke came out from under the dash one night while I was driving. Parked it for a few minutes and could not observe anything peering up into the dash. Started it up again, no smoke continued drive. Owed it for another two years, never smoked again! Everything worked. These cars are possessed.

She (the car) was probably jealous as that was when I started seeing my 'steady' girlfriend. Girlfriend tried driving the car but it always broke down on her. It never broke down while I was driving.
Luis Azan

This thread was discussed between 21/03/2002 and 27/03/2002

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