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Voltage Regulator Test

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  • Voltage Regulator Test

    I had a mechanic replace my VR as a "bad part" but I suspect it is fine. I still have it. Is there a way to test it out to confirm it is good/bad? Or would it require it being hooked up to a car and really not worth the effort? Either way I will hold onto it as I suspect it may be ok.

  • #2
    It's difficult to test the regulator without it being on the car. However I also think it's probably ok. Going by the picture of your engine compartment it appears it may be an original Fomoco regulator. If so it's worth something even if it's just for the cover. It may also be an aftermarket regulator with a repro sticker put on. Either way I would keep it.

    John Pizzi - Squarebirds Administrator

    Thunderbird Registry #36223 856-779-9695


    • #3
      Notice the back of your regulator has two long resistors. They are extremely fragile because they are brittle. When mounted, the resistors are protected but many are destroyed when handled.

      I got a kick out of a YouTube video where you can hear the novice mechanic crack one of these on camera. He had the same idea of testing the regulator on a bench but wasn't careful.

      YES, regulators can be tested but you need to know a few things:
      • What are the resistor values? Are the resistors open?
      • Are the solder connections solid? <--VERY important
      • Have the contact points been dressed and properly aligned?
      • Are the three coils open/shorted or do they pull-in their armatures?

      OEM regulators are all mechanical. They work with either polarity because there are no solid state components.
      I bench test mine using a headlamp for a field load and a battery that is partially drained. If you have questions regarding their operation, please ask. - Dave
      My latest project:
      CLICK HERE to see my custom hydraulic roller 390 FE build.

      "We've got to pause and ask ourselves: How much clean air do we need?"
      --Lee Iacocca