Alternator / Regulator

I have a Piper Cherokee 140/150 1964 28-200119
I just rebuilt the engine and put in a new alternator. Prior to the rebuild I had an infrequent problem of the battery not charging. I thought the new alternator would fix the problem. It has not. Today the battery did not charge during flight. I check the belt and it is tight. Any hints on how to trouble shot this? Thx


  • Hi Pat,

    Sorry to hear about your problem. You might start with some ground run up checks. Running at 1500 with the alternator on, you should see positive flow on the current meter, and 14+ volts on the main bus with a multimeter.

    If these checks don’t pass, problem is likely either the voltage regulator or the over voltage relay. Some of the earlier 140/150s have a mechanical regulator which requires routine adjustment and TLC. You can check the troubleshooting chart In

    Starting with section 4B1

    good luck, and let us know what the problem was.


  • edited June 10

    Pat - I completely agree with Seneca38173. Check the regulator, over voltage relay, and voltages first.

    You mentioned in your original post that the problem was "infrequent". Occasional or sporadic electrical problems may indicate a loose, corroded, or intermittent wire or a bad ground. Also check the alternator switch, and the wiring going to it. It sounds like the problem is probably elsewhere, but don't rule out the possibility that the new alternator may be bad.

    Jim "Griff" Griffin
    PA28 - 161
    Chicago area

  • Senneca and Jim
    Thanks for the direction .. much appreciated. Will be a task for the rest of the week.

    If it is the voltage regulator ... where is it? The parts manual isn't real clear... I believe it is under the panel on the co-pilot side
    either lot's of contortions or disassembly of the panel.


  • Pat, I've seen them under the cowling on the firewall as well as under the panel on the co-pilot side. Yes, the ones under the panel will require you to do some contortions to gain access. Removing the passenger seat helps a lot.

    Jim "Griff" Griffin
    PA28 - 161
    Chicago area

  • Bob, Jim

    It was on the outside wall under the pilot side
    Had to take out both seats for this old body to crawl under ... but got it replaced and working fine now. Thanks for the help


  • Glad to hear it, Pat!

    Scott Sherer
    Wright Brothers Master Pilot, FAA Commercial Pilot
    Aviation Director, Piper Owner Society Forum Moderator and Pipers Author.

    Need help? Let me know!

  • Best news all day. Thanks for the update!!

  • Good job Pat, glad to hear!

    Jim "Griff" Griffin
    PA28 - 161
    Chicago area

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