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Wiring overheats on ammeter circuit (1967)

New User
Posts: 7
Joined: 03/09
Posted: 08/28/15 01:10 PM

I replaced my old dash harness, installed fog lights and pertronix. Started car and wiring was smoking. When I disconnect ammeter everything is fine. What am I overlooking?  

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Posts: 269
Joined: 08/11
Posted: 09/01/15 01:16 PM

The stock ammeter circuit was barely capable of working with stock loads. If you've increased charging system capacity (larger alternator) or dramatically increased the load (electric cooling fan, high wattage lighting, etc.) it will push the ammeter circuit to failure.

The stock ammeter circuit is very dangerous as wired from the factory on the '67 and up Mustangs and honestly it is best to leave it disconnected and wire ends protected. If you REALLY want something to show charging system details, have your ammeter converted into a voltmeter and wire it back into the circuit. You'll be safer and will be able to monitor charging system load easily.

Mark Houlahan
Brand Manager
Mustang Monthly Magazine

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