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Thread: Over Charging Issue, PA-22 Colt 125

  1. #1
    Join Date
    Nov 2014
    Location
    Blue Ridge
    Posts
    5

    Default Over Charging Issue, PA-22 Colt 125

    While flying, noticed amp meter rose to a positive charge of 10amps. Previously amp meter would register very little change from "0" charge or discharge while flying. The over voltage fried the VAL-760 radio apparently. Checked voltage at battery. Battery voltage 12.6 without engine start. As plane is started, all OK. After 1500 rpm, voltage at battery starts to climb and at 2000-2200 rpm, voltage is over 15. Replaced voltage regulator with older style auto regulator to test system (had been Zeftronics). Still over voltage at battery. Will be replacing field wire at Generator to master switch. Have master relay switch on order. This is a 61 Colt with 0290-D engine that has had no electrical problems in the last 5 years. Concord battery less than 3 years old and test OK with load tester.

    Any other suggestions?

  2. #2
    Join Date
    Jan 2017
    Location
    Cashmere
    Posts
    7

    Default

    Dan,
    Here is an article describing a full fielding test for a generator. I haven’t done it on an aircraft, so I can’t add much wisdom there. It does raise the system voltage, so be sure to have avionics and electronics off (not sure what else is necessary).
    http://www.aerotechlou.com/ts_alternators.shtml

    Also, do you have the correct generator on your Colt?

    My Colt has the opposite problem at the moment: My generator doesn’t charge my battery very well. Good luck!
    Just curious, how high of an RPM does it take for you to register no charge or discharge on the ammeter?

    Smooth Flying
    Zander

  3. #3
    Join Date
    Nov 2006
    Location
    Mason, Ohio
    Posts
    352

    Default

    Dan,
    My guess is that you have a short between your generator output and your field wires. This is not uncommon since they are typically run together out to the generator. What typically happens is that the field shorts to the generator output cable so that when the generator turns on, the field is seeing the max voltage and over drives the generator causing it to put out maximum voltage. I would replace both your field wire and your generator output cable from the regulator out to the generator. The field wire runs from the generator back to the master switch under the seat so you may want to splice it someplace inside the cockpit. If the wire isn't the problem, you have a problem in your master switch or with the wiring in the box under the seat. That assumes your regulator is OK which you indicated you checked with another regulator. Make sure all your avionics are off when you test it. By the way the generator typically doesn't put out positive voltage until the engine reaches at least 1500 RPM.

    Tom Anderson

  4. #4
    Join Date
    Nov 2014
    Location
    Blue Ridge
    Posts
    5

    Default

    Thanks to Tom and others who have helped me. First of all, I've been flying for about 50 years, and I still think electricity is black magic. But, I found the problem. After replacing the field wire from Generator, replacing the VR with a "65 Chevy" VR for testing purposes, I still had problem. So, I get advice that I've got a grounding problem somewhere in the cabin. I check the wiring down to the master relay (switch). Anyone try to remove the pilot seat and the master switch? Well don't try, it's impossible. So, while I'm in the cabin, I turn on the master switch and nothing happens. Electrical does not light up. So, I'm thinking. While deep in thought, I put the battery box cover back on the battery box. Suddenly I have electrical power. Removing cover, I don't have power. I play this game of placing the battery box cover on and listen to the gyros wind up, then remove the cover and listen to them unwind. I remove the battery and see about 2 tsp or so of fluid in the bottom of the battery box. The Concord battery (about 30 months old) was leaking somewhere. The battery box was grounding out through the system, at the grounding strap probably, and causing the high voltage requirement from the VR to the Generator. I drove to Spruce, purchased a new Odyssey battery. Cleaned and repainted battery box, built out box to accommodate the new smaller battery, tied up everything and fired it up. Voltage at battery, with no power on plane was 12.65. With idle power 12.86. Full power only 13.45. Before, the voltage would climb after 1500 rpm to over 15 volts.

    I test flew the plane and measured voltage at battery and did not get over 13.5. Amp meter did not register more than +2-3 with strobes on.

    Notes:
    1. Start trouble shooting at battery when electrical problems occur -- not necessarily at generator.
    2. Call all your friends to help with the "thinking"
    3. Repair your VAL 760 radio at VAL Avionics rather than replace if money is a concern. They are great people who fixed my fried radio for a reasonable cost. By the way, the radio has an internal fuse that will fail when voltage is over 18-20 volts as I understand.
    4. Buy Odyssey battery when you need replacement.

    So, I'm back up and flying again... Thanks to all who helped me through this problem.

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