Club Homepage Forums Classified Ads Buy & Sell - Everything But Airplanes Need an alternator for an O-200-A

My 1500-or-so hour-since-new alternator crapped out on me today, so I need a replacement. I'd appreciate any suggestions about where I might be able to get either a new or rebuilt one, or even a surplus used one. Or, if that's not possible in a reasonable time, where I might send it to be rebuilt. It's got about 12 volts on the field terminal but isn't charging the battery. Based on auto experience, I'd guess it's a bad diode, but I don't have any evidence for that.

It's a 60 amp gear driven unit. Although my plane is a 1967 G model, the engine is just a few years old if that makes any difference.

Thanks!

Roy

Plane Power has some good troubleshooting flowcharts. It'd be good to work through the appropriate flowchart to verify it's the alternator and not some other component that's causing the charging issue, before throwing money at repairing or replacing it.

https://planepower.aero/aircraft-alternator-support/troubleshooting/

Aerotech of Louisville and Aircraft Electrical Components in CA can rebuild them. Alan

Thanks, I really appreciate that. But it confirmed what I'd concluded -- that if the alternator field terminal has about 12 volts (the troubleshooting guide said that 1 to 1.5 volt drop through the regulator from the supply voltage is ok) and the alternator output (battery) terminal has (the abnormally low) bus voltage, then it should be putting out current to raise the bus and battery voltage. Of course, that's also assuming that the battery and alternator grounds are intact which they are. I'd be really, really happy if the problem was something else, but no matter what else might or might not be going on, the alternator flunks the basic test.

Roy

If it's the alternator, you can decide between overhaul or repair as needed. Either way, you could pull it apart to see what's wrong with it before sending it out.

If it was a car alternator, I'd take out the brushes to see if they were too worn and not making contact anymore. They're so cheap (and I once got stuck in the middle of the Arizona desert towing an airplane wreck), that I replace them every 60,000 miles as a preventative measure on my cars. A few years back, just to see, I took some aircraft alternator brushes into a local shop and was handed a new pair for $3.58. Since it was an experimental aircraft, that was a cheap repair.

I have a confession to make.

When I bought a new engine a few years ago, it came with a new alternator. I was working with my mechanic on the installation, and was attaching the field wire to the alternator -- and sheared the protruding bolt! After 60 years building countless homebrew projects as an amateur radio operator, several as a military radar technician, and repairing all sorts of electronic, electrical, and automotive products, I know how tight to torque a #6 or #8 nut! And never before in my life have I ever overtightened one enough to shear it. I disassembled the alternator to see if the bolt could easily be replaced, but it was a very strange custom bolt that served other functions internally. We went to reassemble it, but neither of us could overcome the challenge of holding some items in place while putting the cover on -- it apparently required a specialized jig or some trick we couldn't figure out. We ended up sending the pieces to a rebuilder who replaced the bolt and reassembled it.

That was very humbling. Many years ago I had an alternator problem in my '61 Dodge, disassembled it, located a shorted diode, got a replacement, and managed to extract and replace the pressed-in diode. The alternator ran flawlessly for many years after that. But after the experience with this alternator, I'm not going to mess with this one.

But this caused me to recall the experience, and I'll try to dig up the name of that rebuilder. He did a good and prompt job for what I recall was a reasonable price.

Roy

Ordered mine from Aerotech 3 days ford DOFF101300-F.

Aircraft Spruce for a service exchange.

https://www.aircraftspruce.com/catalog/pnpages/07-06415.php

They give you core on the old alternator.

Thanks very much, everyone.

I decided against an Aircraft Spruce overhauled unit because numerous reviews of several different types they sell claimed that they failed after a short time. And they do have a new Hartzell ES-4001 (which is what I'm replacing) in stock for only $250 more than the overhauled DOFF10300FR. I called the company that repaired my alternator six years ago about an overhaul, and it would take 2-3 weeks and probably cost around half what a new unit would. But they had a new ES-4001 in stock they could ship immediately, at about the same price as Spruce's. Much as I love doing business with Aircraft Spruce, I chose to go with the smaller company who also provided super service in the past. That company is Aircraft Accessories of Oklahoma.

Thanks again!

Roy

The alternator is on and working. Thanks again for all the info.

Roy