MG Car Repair: Wiring Short in MGB loom, alternator problem, brown wires

Question
I have a 1978 mgb.  I was installing a new alternator and forgot to unhook the battery.  There was a small arc now after putting another Alternator in, the battery drains over night. Where is the "best to start looking for the short.

 Thank You,
Jim

Answer
Hi Jim.  I would start by unplugging the alternator.  If that stops the battery from draining overnight then you have blown one or more of the diodes in the new alternator.

If you still have a drain with the alternator unplugged then you will have to trace the leakage.

Was everything OK before you had the alternator problem?  I ask because usually a slow drain is caused by something else such as the light in the boot (trunk) staying on.

There are two thick brown wires that both go directly from the alternator to the starter motor.  It is just possible that one of these wires got so hot that it melted the insulation.  Unfortunately, you would have to unwrap the loom and check those two wires individually.

Please let me know what you find.