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external voltage regulator replacement and wiring ?

greenthumb's Avatar
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04-21-02, 12:21 PM   #1  
external voltage regulator replacement and wiring ?

re: 1969 Mercury Cougar.
351-2v engine.
Automatic transmission.
Equipped with A/C, but not functioning.

After an engine replacement, the ALT light remains on. (Sometimes, after a lengthy drive, the light will go off.) I am fearful that wiring to the external voltage regulator may have gotten mixed up when the engine was replaced. The repair shop that did the engine also replaced the alternator and the voltage regulator. A second alternator was installed, with the same results. Now I wondered if the first alternator is even bad...

The battery is charged with a charger each evening and the car does "okay" the following day as long as the lights are not used. But the ALT light remains on for 98% of the driving.

I am ready to replace the voltage regulator again, but I am concerned about which wire goes to which terminal. The Chilton manual that I have is too generic and does not address the wiring details.

Prior to the engine replacement the car had NO electical problems.

I have a multi-meter that reads ohms and volts, but I am not sure how to use it to assist in trouble-shooting this problem.

Your assistance is much appreciaited !!

jeff from costa mesa, california

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marturo's Avatar

Join Date: Jun 2001
Posts: 1,448

04-21-02, 01:53 PM   #2  
Voltage Regulators

Hi greenthumb

I work on 67 to 72 Chevy Cars & Trucks. The External Voltage Regulater is dead I use the internaly regulated modern one wire, Alternator with a $27.00 Inside veltage regulator. Then you just hook one 12ga wire to POS side of Batt and the POS terminal of your Alt, and never worry again about any external stuff.

If you don't have a modern Alternator laying around, you can order one ready to go, from http://www.summitracing.com they offer this one wire alternator, for a direct replacement for older & newer cars & trucks. This $27.00 inside one wire, voltage regulator, will not work with any externaly regulated Alternator, only the newer Alternaters that have the voltage Reg inside. In Chevys I think it's 73 or 74 and up

I have tried all the hybrid new type plug in from the outside to get closer to modern type voltage regulation. Get the One wire Alternator, and just replace your front and rear bearings, and brush & brush holder once in a while, & that's all the Maint there is to do. I have one on my truck that I have rebuilt twice & no problems with the voltage Reg. Every 30,000 I replace my Bearings and Brushes for all of $15.00 small price & easy job keeps my batteries happy with long lives.

Make sure you match your amp output, like any car or truck with, AC it needs the higher output to work the extras. If you don't know what Amp size you run, just buy the one for the AC models. It won't hurt to have more wattage, it just won't make it if you don't need it.

Happy charging

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04-21-02, 05:04 PM   #3  
I agree with Marturo, and especially so if originality is not a concern on this vehicle.

Ford's charging systems have always been hokey with those external regulators (an old design they perpetuated for years).

Also, just because you got a new alternator doesn't mean it's not defective. Auto parts store rebuilts can be bad out of the box...I rebuild my own like Marturo states in his post.

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