93 Mustang Charging Issue - Intermittent

emba129_98

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Hi all, I was driving my 93 cobra last weekend in the 90 degree weather. went to a few places. On the way home, the battery light came on and the volt meter was barely above 8VDC. The battery is brand new, but got drawn down to the point of the car quitting luckily just when I got it home.

When the car is cold, the alternator is charging properly at about 13.8v. Seems to happen when the car is hot.. intermittently.

The alternator is a remanufactured Motorcraft. I assume a stock 75A unit. I dont know how old it is, but the car has only 64K miles on it. Seems newer. See pics

Im going to bring it to Autozone for a bench test. I am suspecting it will show good since I think the failure is high temp related. Im suspecting the voltage regulator is bad. Would you recommend replacing just the regulator or a new alternator. Looking for recommendations on good replacement parts/brands for both.
 

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Mustang5L5

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That's not a stock 2G 75A. That's a 3G 130A alt. 94-95 Mustang GT would be the application

While i would supect voltage regulator here, your wiring is also suspect. Was that how you received the car? The double 10G wires crimped into a single loop crimp should be cut back, taped up and tucked back into the harness and not used. They are undersized for 130A and a fire hazard if used.

Instead, you want to run a 4G wire with crimped ends from the power stud over to the starter solenoid. That will give you safe wiring.

Also, the blue spade style butt crimp fits over the stator plug on the regulator which essentally turns it on/off. If this connection is loose, you will have regulator issues, so you want to make sure the connection is clean of corrosion and tight.

If you want the correct connector for that plug, this is it

When undersized wiring heats up, it's resistance increases which contributes to voltage drop. Is that what's happening here? Hard to say, but regardless, running the 3G alt with the two #10 wires only is a potential fire hazard. I would correct the wiring, and then see if the voltage drop issue still exists. If it does, then i would replace the regulator.
 

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