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Thread: Electrical Charging Question

  1. #1
    Join Date
    Jan 2020
    Location
    Tiffin, Iowa
    Posts
    3

    Default Electrical Charging Question

    Original dual-throw master switch. PA-22-150 Tri-Pacer will start but with RPM advanced may not show a charge.

    Tested generator and voltage regulator and am confident they are good.

    Initially thought "wiggling" the generator CB would produce a result on the ammeter so replaced the generator CB with the same version. Worked for a while.

    Now, again sometimes ammeter showing no charge at cruise RPM. Fiddling around with the master switch I now think I can cause the ammeter to show a charge and then subsequently with more fiddling it will show discharge.

    My question now is what is the general experience with opening the master switch box? It is likely the switch can be cleaned or repaired? What are the chances that an identical replacement can be found, what is the part number, what does it cost and where can it be obtained?

    Thanks

  2. #2
    Join Date
    Nov 2006
    Location
    Mason, Ohio
    Posts
    350

    Default

    My guess is that you have a loose / broken / ready to short field wire. I would start by checking all the wires in the box under the seat. Aslo, do you get the same result with the switch in the alternate position (up versus down)? A new switch from Univair is about $130, but my guess is that it's a loose or almost broken field wire or a connection that has worked loose. If the field drops out you should see a discharge. You can find the new switch in the parts catalog in the Maintenance Data Depot, which you get to through the web site. The parts catalog is now the interactive version which is linked to Univair if you click on their part number. The standard Piper part number is also given.

    Tom Anderson

  3. #3
    Join Date
    Jan 2020
    Location
    Tiffin, Iowa
    Posts
    3

    Default

    Tom,
    Again today I had a long time when no amount of changing switch positions or "fiddling" would cause the ammeter to show a charge. After a number of times switching form the top to the bottom position, suddenly I got an ammeter charge. How much trouble is it to open the box? Does one remove the box from it's mount or open the box in place? I wish it were warmer in the hangar.

  4. #4
    Join Date
    Nov 2006
    Location
    Mason, Ohio
    Posts
    350

    Default

    Opening the box is simple. There is a small latch screw in the front center lip of the box. Give that screw a half turn to the left and the box lid should slide out and can be lifted off. You may want to remove the pilots seat if you are going to do much work in the box, but you can just move the seat all the way back for some better access if all you are going to do is look. If you get into moving wires or disconnecting wires you may also want to disconnect the battery to prevent any shorting. There isn't much room in that box. Make sure you understand the wiring diagram that is in the owner's manual before you get into the wiring issues. Also, I am sure you know that the two main fuses for the electrical system are there as well.
    The switch is a double pole double throw switch and there is a connection to each of the 6 terminals. There isn't any way to lubricate the switch, so if it's bad, you will probably have to replace it. My guess is the switch is OK, but you have a loose or shorted wire going to it. You might also check the wires going to the regulator and the field and armature wires coming from the generator to make sure they are not broken or shorted. Also, if you have a standard generator you should know that it doesn't start putting out until at least 1200 - 1500 engine RPM.

    Tom Anderson

  5. #5
    Join Date
    Jan 2020
    Location
    Tiffin, Iowa
    Posts
    3

    Default

    I opened the box per your instructions and found all wires look good and all connects are solid. I did not take anything apart.
    If I have to open it up, how do I disconnect the battery?

  6. #6
    Join Date
    Nov 2006
    Location
    Mason, Ohio
    Posts
    350

    Default

    The battery box is under the front seat. The wiring diagram is in the owners manual. If you need a copy, it is available on the Maintenance Data Depot under Miscellaneous. I suggest you study the owners manual or find someone that knows something about short wings. While this stuff isn't rocket science, it helps to understand the systems before you try and troubleshoot them.

  7. #7
    Join Date
    Jun 2019
    Location
    Marana, AZ
    Posts
    10

    Default

    My Tri-Pacer seems to do the same thing. I have found that the amp gauge really just shows the amps the generator is pumping into the battery. When I first start out it will show that the gen is pumping amps to the battery, but after awhile it will show nothing, but my little gauge in the cig. lighter still shows 13 +. The gauge is basically telling you what the gen is doing, if the batt. is fully charged then the gauge is pretty neutral, but if I throw on the Landing lights then the gauge will show that draw.
    I have learned that if the gauge is showing neutral then my battery has been charged and the regulator is working on keeping the battery charged and not trying to over charge.

  8. #8
    Join Date
    Oct 2005
    Location
    Graham, Texas
    Posts
    901

    Default

    Sounds like to me Coastie13's generator system is working correctly.

  9. #9
    Join Date
    Sep 2017
    Location
    Lynchburg,Ohio
    Posts
    1

    Default

    I recently replaced my Colt master switch. This is the second switch I've gone thru. Univair sells them $120 or so. I got tired of that so this time I installed a switch /circuit breaker in place of the original. I think it was 30 amp about $40. The 8 or wires coming off the original can be intimadating. A Colt schematic is a nice source. Most of those wires meerly connect the top switch with the bottom switch on the original. They are jumper wires. My one big fault was not recognzing 1 theminal connects the generator field with the bus bar. That's in case the generator decides to put out 15 volts so you can turn off the master and turn off the field at the same time. When you flip the switch it turns on the 12V to the field and it is ready to charge. After I isolated the field wire I ran it to a 5 amp circuit breaker on my circuit breaker panel. Its a pull breaker so If I need to turn it off due to overvoltage I can just pull the circuit breaker, Also is an over voltage occocurs the circuit breaker will trip, throwing the field off the circiut. If you have an alternator it may be some different. Now you know enough to be dangerous! Keep flying. Ralph Widman

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