I just replaced the alternator in my 67 I-200 Mustang, and it is constantly charging, and boiling my battery.

Any suggestions on how to start trouble-shooting this?

Is the blue box behind the left headlight bucket the voltage regulator, or is the voltage regulated internally?

Thanks!

Drew

 

Check your wiring carefully. If you put 12v from the battery to the Field terminal, you will essentially be performing a "full field" test which provides maximum output from the alternator for testing purposes. This is not good if it happens for very long. You could see over 16v while this is happening. My guess is you are either full fielding it, or you have a bad regulator, but I don't think the regulator would cause it to boil the battery.

 

You didn't say, but I assume you replaced with the original type alternator, right? Not a one-wire or some universal type? It is the original Ford style for that year right?

 

I purchased an alternator that looks exactly like the one that was on it from O'Reilly's.

I asked for a 1967 Mustang six cylinder alternator and it is what they gave me.

I swapped it over, wire for wire from the original.

 

they should have tested your old alternator before selling you a new one and they should have tested the new one as well ...

 

It still sounds like you are getting full field from somewhere. Have you measured the voltage at the battery while the car is running? Up to 14.6 is normal. Beyond that and you are likely overcharging. Like I said earlier, if you are seeing in the neighborhood of 16v, you either have a misplaced wire or a short to power on the field circuit.

 

So, I pulled off the old (original) regulator, just out of curiousity. One of the thermistors on the back of it had been burned completely through and the amount of corrosion in the burn indicated it has probably not worked for a decade or more.

So, a new regulator and I am back pushing 14.5V.

Here is my theory: The alternator was in such poor shape that it probably wasn't providing a full 14 V, which allowed the dead as doornails regulator to not matter that much. I showed it to a mechanic and he had the same theory, without prompting.

 

The reason I pulled the old one was that it was shucking a bearing with extremely noisy enthusiasm.

This is a survivor car that has been mainly parked since 1987. Now that I've started driving it, all the accessories have taken a physical dump in sequential order.

So the only thing original up front is the engine. Which is running really well, btw...