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MG Car Repair/Wiring issue

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Question
I am restoring a 1972 midget that ran before I started working on it. I purchased a new wiring harness and starter from moss motors and also a brand new battery. After installing the new starter and hooking up the new harness I am having major trouble. The ground wire coming off of the ignition switch shorts out the second I try hooking it up. Also possibly related or not if I try to hot wire the starter solenoid I get a loud click from the starter but it wont turn the engine I am at a loss and any help/ideas would be greatly appreciated.

Answer
Hi Donald,

Have been faced with that type of problem many times in dealerships when a new harnes was not exactly like the one we were replacing.

It made it necessary to use a "In-line" fuse between the battery and the battery cable. It can be put on either the positive or the negative side. This method allows you to test each item in the electrical system without the worry of melting the new harness or making a lot of sparks when there should not be any. The only item you can't test with this in place is the starter (That should be tested last anyway).

You need a 12v test light (or a volt meter) and a wiring diagram of your car. Following your wiring diagram connect up ONLY one circuit at a time and confirm that the color code of the wires being connected match the color code on the diagram. If one does not match STOP!! do not connect it. I start by laying out the harness where it is suppose to go and I then connect my "In-line" fuse and the grounds (black wires), then I look at the diagram and pick a circuit to connect. This usually means you need to connect the fuse box wires and usually a switch that operates the first item. For example a heater fan or the head lights. Then I test that switch to see that the item works. If the item does not work use the diagram and test each junction in that circuit only to see where you lost either power or a ground. When you get that item working move to the next item that you chose.

Soon you will have every item working except the starter motor. And the charging system because you can't test it until you get the engine running.

To test the starter motor (after you have the whole car wired and tested) Take the 12v test light and confirm that you have power on the large battery cable on the starter solenoid. Then turn the key to "Start" while you have the test light on the large post on the solenoid that goes to the starter motor. When the solenoid goes "Click" the test light should light up. If it don't light up the solenoid is bad and if it does light up brightly and the engine did not try to turn over then you have a bad starter motor. (sometimes you can just remove the starter motor and remove the end plate and clean up and free up the brushed and take Emory paper and clean the comutator on the armeture to correct a starter that has been setting a long time. Also you should put the car in 4th gear and rock the car forward and backwards to confirm that the engine is not locked up from surface rust on the cylinder walls.

In the dealerships we often received cars that had been stored for some time and were locked up.

Let me know,

Howard

MG Car Repair

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Howard M. Fitzcharles III

Expertise

MG from 1956 (USA versions only) up and Engine theory.

Experience

Dealership line mechanic on MG, Triumph, Jaguar for 15 years, Instructor in commercial mechanics school 2 yr. Product information manager for piston and valve manufacture, Instructor & hotline answer man for import car parts importer 15 yrs.

Organizations
Associate member SAE EAA member

Publications
Import Car magazine

Education/Credentials
ASE Master Auto with L-1 certification up to 2000

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