|The MGA With An Attitude
GROUNDING POINT Preparation & Cleaning - ET-103B
At 02:18 PM 4/28/05 -0400, William Mitchell wrote:
>".... Shorts seemed to be happening more and more often. "
Ow! If you have any short between wires inside of the harness jacket, it's probably time to throw the harness in the trash. Wires inside of the harness will never fail unless something externally shorts out causing high current flow which may melt the wire insulation. Otherwise ALL harness problems will be resolved at the end connectors. Never cut open a harness jacket unless you have verified with ohm meter or test light the wires are broken or shorted together.
Loose connectors and bad grounds are almost endemic in these old cars. You can learn to fix those things, and with some finesse fix them so they (mostly) do not happen again.
For screwed in place ground connections, sand down to a clean bare surface, and attach securely with clean plated fasteners. For good measure a little dab of silicone grease can help prevent corrosion where you just exposed bare metal, but even without grease, rust should never spoil the ground connection if the fastener was properly secure. I have seen amazing cases where rust has eaten all metal away completely around a screwed together ground connection, but there remains a solid ring of sheet metal within the screwed together joint.
If you don't want to remove paint, an alternative is to use an external tooth star washer to cut through the paint to contact the base metal. This requires a new star washer with very sharp edges, and should be checked with an ohm meter after installation to assure a good electrical connection after it cuts through the paint. A dab of silicone grease is highly recommended to prevent corrosion, as the contact points are very small (and the grease helps prevent corrosion from creeping under the paint). Internal tooth star washer is not recommended, as the teeth are usually too small or thin to do a good job of cutting through the paint. However, you might sand off a small spot of paint around the hole where the internal teeth could get a bite, then add dab of silicone grease, and it could work while leaving nice appearance around the fastener.
For bullet connectors, chemically clean the male bullets, install a new female connector shell, and fill the thing with silicone grease. The bundle of bullet connectors aft of the right rear tire may be tape wrapped to protect it from road splash. Use harness wrap tape with no adhesive.
For the "gawd I hate" Lucar spade connectors, throw them all in the trash and solder the wires together. Otherwise chemically clean all contacts, crimp the female connector a bit to be a very tight install, add a dab of silicone grease, and put it on your preventative maintenance list to re-check them all at least once per year. High current circuits will give the most problems, like battery supply to (aftermarket) ignition switch, headlight circuits, and dynamo output. As far as I know, there is no such thing as a permanent connection with a Lucar connector.
For screw post connectors, clean once, assemble securely, and forget it forever. Gotta love those grub screws and hex nuts. I have never known one to fail, short of breaking the wire.
There are two lamp fixtures on the MGA dash that do not have a ground wire and rely on contact with the dash panel for grounding. The turn indicator warning lamp housing grounds on the flat back surface of the dash with minimal contact pressure (secured by the screw-in plastic jewel only). The back of the dash must be clean to bare metal here. I cleaned the paint off after restoration in 1986 and haven't had any problem with it for 20 years. The latest replacement lamp assembly from Moss Motors includes a grounding bracket with a screw for a supplemental ground wire to be used if the dash is made of some non-conductive material such as wood or fiberglass. See: Replacement Parts. The map light lamp socket plugs directly into the steel dash panel. Here you only need to clean paint off of the perimeter of the hole in the panel where the bulb socket spring fingers make contact.
I installed a new harness with (the first) restoration of my car, and had virtually no problems for about 5 years 50,000 miles. First problem was the bullet bundle aft of the RR tire. About the second time I had to crawl under there I cut off the bullets and installed gas tight crimp-on butt connectors, and no more problem there. Common automotive crimp connectors are sort of hit or miss, depending on your skill and experience with the crimping tools. I'm pretty good with it, but lots of people aren't. I have never had harness grounding problems, but there may be some issues with body ground for the corner lamps. For a while some replacement front parking light fixtures were being supplied with no ground wire.
There are some other connection issues related to lamps in particular. For plug-in light bulbs, filling the bulb socket with silicone grease can eliminate 90% of all lamp fixture problems. For the three-spade headlamp connector, a good cleaning and filling the sockets with silicone grease helps a lot, especially if you do it when the socket it new. Otherwise these connectors are much like Lucar connectors, so when they go bad it's best to replace them.
The really pesky connections on the MGA are the little curled female bullet receptacles in the tail lights and license lamp (and sometimes a ground in the front parking lamps). Those carry enough current to overheat with the slightest corrosion, and once heated will loose the spring temper and are permanently shot. The only cure is replacement of the lamp fixture. Best prevention is to clean the parts, assure the tightest possible mechanical joint, add a dab of silicone grease, and keep the covers and gaskets and rubber boots in good condition.