1938 Cadillac Viltage Regultor adjustment

My battery is being overcharged, as I can see water coming out vent caps, and hissing when engine running!.

8.6 Volts at idle, 9.0 at speed, and 6.6 with engine off.

Maybe my Voltmeter is off, all all readings are in spec, if I deduct 1 volt for meter error.

In any case, any help understanding VR setting will be appreciated.

Bob Martin

First off what model voltage regulator are you running? In general Delco Remy voltage regulators are adjusted by putting a variable resistor in series with the battery or by replacing the battery with a 3/4 ohm resistor and then adjusting voltage regulator by bending the spring hangers or if voltage regulator has them turning the adjustment screws. This is shown in the shop manual.

Not sure, will have to take off to see. Cant see any markings on it. Its the original one on the car.

Can I just put Volt Meter on Battery, and adjust Voltage Regular for spec numbers, which I have,

Thanks, Bob

In a word, No. The reason that resistors are used is to get a constant load. The amount of current a battery draws will vary as the applied voltage is changed. The regulator is adjusted with the generator supplying a constant current. There is a test to find out if the over changing is caused by the voltage regulator or by the generator/wiring. Run the engine at about 20 mph. Remove the wire from the regulator field terminal. If the changing rate now drops to zero, the regulator is at fault. If the high changing rate continues with the wire removed from the field terminal of the regulator, the generator is faulty or there is is a grounded wire in the wiring harness.

Replaced the Voltage regulator. Charge back to normal. Thanks, Bob