Rusty Nuts Data Page

One-wire Alternators 


One of the best articles that I have found to explain the GM/Chevy Alternators is at :

Be sure and check it out before you wire your street rod or custom.

Below are a few comments  that were sent to me a couple of years ago.

Q – How do I hook up a one-wire alternator if my stock alternator was an externally regulated alternator? What do I do with the regulator and wiring harness?

 A The only thing required to electrically hook up a one-wire alternator is to run a charge wire from the battery terminal on the alternator to the positive terminal on the battery (or any positive battery source).

The external regulator can either be totally dismantled from is current location or left in place. If you leave it in place, be sure to disconnect the wiring harness from the regulator. The harness has to be disconnected from the regulator or the indicator light on the dash will remain on. NOTE: If the car is equipped with a indicator light, the light will no longer be functional when running a one-wire alternator. 

QWhy do I have to “rev-up” my engine to get my one-wire alternator to come on?

 A A one-wire alternator has a turn on point (sometimes referred to as “cut-in”) that is typically around 1200 engine RPM ‘s.  This is the speed where the internal sense circuitry connects the battery to the voltage regulator, thereby turning the alternator on.  Once the voltage regulator turns on, the alternator will remain on and charging until the engine comes to a complete stop.  If the engine idle speed and pulley ratio combination does not allow the alternator to come on to this point during starting, the engine will have to be revved up to turn the one-wire alternator on. 

Q Will aftermarket pulleys (power pulleys) affect the output of the alternator?

A Yes!  Especially when using a one-wire alternator.  Changing the pulley ratio of the alternator by slowing it down will generally keep the one-wire regulator from “cutting on”.  This may also produce a low voltage problem at engine idle speed depending on the amount of reduction.  Alternators are tested with a 3:1 pulley ratio in mind.  This is the recommended street pulley ratio and is used in most OE applications.