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MG Car Repair/no power to the instruments 78 mgb


i have a 78 mgb my problem is there is power to the bottom fuse but no power to the other circuits. i have checked the fuses, jumped power to the green wires and all of the instruments worked fine. i checked the other circuits and have no power from the ignition relay to the fuse block. i have been using your wiring diagram as a guide but have reached an impasse. i know i'm missing something just don't know what.

Hi Seth,

I learned that you should forget about trying to diagnose any electrical problem by symptoms. Concentrate only on ONE circuit that does not operate. I always start at the load (item that does not operate) and with the diagram take your 12v test light and check one joint connection at a time heading toward the source (battery).

Most of the time when you have several circuits that don't operate when you correct the ONE you are tracing, it will correct the others too. Do not try to think what it might be.

Using this method, it is impossible to fail to correct the problem. When you have several circuits that have failed pick the easiest to trace and ONLY trace that ONE circuit. If you correct that ONE circuit and it does not correct the others just pick ONE more and do it again.

This method is a 100% fix rate.


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Howard M. Fitzcharles III


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


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.

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