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Voltage regulator trouble?


Dan Reed
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I just replaced the alternator and voltage regulator on my "64 Cadillac. Everything seems to be charging correctly (12 volts at bat. with car off, 13-14 volts when the car is running) Odd problem is that the volt. reg. is causing the GEN light to come on while driving at certain rpms, it blinks on as I slow to a stop. Then blinks on again as I take off from a stop, but stays off while cruising speed. Then when I park and turn the car off the GEN light comes on! I can only get it to go off if I disconnect the four wire plug on the voltage regulator. What's the deal?

 

Dan

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4 hours ago, Dan Reed said:

I just replaced the alternator and voltage regulator on my "64 Cadillac. Everything seems to be charging correctly (12 volts at bat. with car off, 13-14 volts when the car is running) Odd problem is that the volt. reg. is causing the GEN light to come on while driving at certain rpms, it blinks on as I slow to a stop. Then blinks on again as I take off from a stop, but stays off while cruising speed. Then when I park and turn the car off the GEN light comes on! I can only get it to go off if I disconnect the four wire plug on the voltage regulator. What's the deal?

Dan

 

If you are using an OEM-type 3-coil mechanical regulator, then this may apply. 

If you are using a more modern solid-state regulator, then never mind.

 

It sounds like the 3rd coil (battery cut-off) may be sticking closed, or has another method of maintaining contact (conductive debris at the points or something similar).  It could also be that the coil spring tension is adjusted slightly off. 

 

If this is what's happening, the battery would stay connected to your generator after you turn the engine off.  This causes the GEN light to go on.  Please be aware that if this is whats happening, your battery could be draining...fast.  This is a real fire danger.

 

When the RPM is low, the 3rd coil points should open if your generator output is too low, so again, the GEN light will go on.   Fickering is very common for these type of systems.

 

That's my guess at this point, so-

1.

Until you know for sure what the problem is, and because it could be a fire hazard, disconnect the battery when the car is not running.

2.

Open the regulator case and visually inspect the coil contacts (points).  Does the 3rd coil tend to stay closed?  Is there any debris?

3. 

If faulty, fix the issue, but only if you know what you are doing!  Otherwise, get another regulator.

 

Diagnosing via internet is slippery slope.  Electrical  is even tougher.  Good luck.

 

 

 

 

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 Real steel is on the ball. Why not just replace the alternator with a  Delco 15 S1  65 amp or 90 amp alternator with the integral regulator  ? Leave the old mechanical regulator in place . You will be able to use the same wires from the block and wire the new alternator and keep the old antique look. Playing around with the old mechanical regulator is trouble. The electronic one cannot be repaired and must be replaced. 

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These Delco  alternators are fairly inexpensive and widely available. Most alternator rebuilders are actually throwing them out in the garbage. It is the most reliable alternator ever built except Leece Neville. I rebuilt dozens for transport  tractors.

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Thanks everyone. Trini, I took your advise - I picked up an internally regulated 3-wire alternator and wired it up this morning. Charging correctly and all systems seem good to go. Car ran fine and GEN light operates as it should coming on momentarily only at startup (or if key is turned to run position).

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You will never regret it. The alternator will  also charge at lower engine speeds and if you want it to  charge at still lower speeds you just have to use a smaller pulley. Before I forget I would like to tell you something.  Look just below the bearing (wire side) and you will see a small slightly oval hole about 1/8 size. By pushing a stiff wire hard inside ,and at the same time grounding it to  the frame you will be grounding the field and the alternator reading will shoot right up. Use a volt meter to do that check. That is the way to diagnose a sick alternator. Which I hope you will not have to do a for a long time.

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