O-290-D Alternator Conversion

[8359]

Circling back here, does anyone have the Alternator Conversion STC they'd be willing to look over for me? Just wondering if there are any provisions for other engines? Or if I'm chasing another dead end. I'm getting a little restless waiting for the FSDO to re-open.

Unfortunately the auto-electric shop gave away their voltage regulator tester a couple years ago and they didn't want to touch it. I opened it up, cleaned all the contacts and re-gapped everything per the delco-remy bulletins (Thanks for the help offline Edd). I then bench tested it and it appeared to be opening and closing as spec'd. However once I got it back in the airplane I had zero response from the system when rev'ed up to higher RPMs. I think I may have permanently damaged something :/ I think I may have reached the end of the road here.

Thanks for the help everyone. Hopefully the gov re-opens soon and they aren't so back logged that it takes months to get back in the air.

[6643]

I think I may have reached the end of the road here.

Are we talking about the generator here? Have you tested the generator? I thought you had the system working. Now it seems you're saying it's not functioning at all.

Do you know if the regulator is providing the ground for the field winding, or the hot? (Is it a Type A or a Type B generator?)

Oh, by the way, I'm not sure what STC you're looking for, but it is extremely unlikely you'll find an STC for the 120/140 that covers both the C series and the O290.

[8359]

If you go back a few pages you'll see that I was able to test the system and got full output from the generator when the I grounded the field. So that lead me to the voltage regulator as the problem. I (incorrectly) tried to re-polarize the system and after that haven't been able to get it working again. I then removed the voltage regulator (details in post above) in an effort to try to fix it, but have had no luck.

I was looking for the STC that called out the C120/140 to see if there was any room to be able to apply it to my motor, but I think that's a dead end.

I know this is turning into a train wreck. Anyways, thanks for the help. I think I just need to be patient and wait.

[6643]

OK, so grounding the field wire makes (made) it go to full output. You have a type "A" generator. (Same as the Continental setup, in fact, you could be using the same regulator.)

1) Take all the wires off the generator. Put a volt meter between the "A" terminal of the generator and ground. Set it to a range no less than 15 volts, DC. Start the engine. The meter should read something like +1 volts. The exact value is unimportant. The polarity is important. If you get a positive voltage, skip to step 3. If it's negative or zero, go to step 2.

2) Negative voltage indicates the generator is polarized backwards. Zero indicates it's not polarized at all or it's bad. (If this is the second time through this step and you still have zero, it didn't work the first time and it won't work now; the generator is bad.) To polarize the generator, put a jumper wire from the field terminal to ground on the generator. Briefly connect a jumper between the battery + and the "A" terminal (2-3 seconds). Repeat 3 times. Go back to step 1.

3) If you got a positive voltage in step one the armature is good and the generator has enough residual magnetism to self excite. Connect a jumper from the "F" terminal of the generator to ground. Connect the volt meter as before, from "A" to ground. Start the engine and observe the voltage. It should follow engine RPM and should exceed 14 volts by about 1500 RPM. If it does then the generator is working.

The case of the regulator has to be grounded. It is mounted in rubber but there should be a tab that provides a connection to one of the mounting screws. Be sure it is there. With everything off, your meter (Ohms or continuity function) should show a connection between the "F" terminal on the regulator and the case. When you open the contact points of the voltage regulator coil (the one with the fine wire winding) There should be several ohms resistance between "F" and ground.

Let me know if you get this far.

[6643]

If the system is working at all then it doesn't need to be "polarized". Generators are self exciting. The pole shoes of the field retain some residual magnetism which allows it to generate enough current to feed the field coils, which allows the voltage to build up to the point where the battery can be brought into the picture. Otherwise, the battery would discharge through the generator whenever the generator output fell below the battery voltage.

The polarizing process (called "Flashing the Field") feeds current from the battery through the field windings in the normal direction and magnetizes the pole shoes. If you feed the current backwards the poles will be reversed and the generator will reverse polarity. The regulator will never connect it to the battery as the results would be spectacularly disastrous...

[8359]

Thanks for the detailed response John. I'll try to get to the airport in the next couple days and see if I can get it worked out and report back.

[4004]

Tamer, I wrote a detailed response but erased it all in trying to edit!!!
Note John C diagram - V and I reg points closed until engine running, air gap is for operating state.
Any fuses blown?

Edd

[8359]

Tamer, I wrote a detailed response but erased it all in trying to edit!!!
Note John C diagram - V and I reg points closed until engine running, air gap is for operating state.
Any fuses blown?

Edd

Sorry about that. I will go back and double beck those gaps. Thanks for posting.

No fuses blown.

[6643]

The regulator has three functions: voltage regulation, current limiting, and reverse current cutout.

The voltage regulator is the coil with many turns of fine wire.The points will be closed until the generator voltage output reaches the set point, about 14 volts, at which point they will start to vibrate. When the points are open there is a resistor introduced into the field circuit that drops the output. The mount of time spent closed relative to open controls the average current through the field windings and hence the voltage.

The current limiter is necessary since the generator supplies its own field current, and, if the load is too high, may self destruct trying to maintain the set voltage. The current limiter works the same way as the voltage regulator, except it responds to current output. It is the coil with a single heavy wire winding. The current limiter has to be matched to the generator's rated output.

The reverse current cutout prevents the battery from discharging through the generator when the generator output voltage is lower than the battery voltage. It is the coil with two separate windings. It is open when generator output is low and closes, connecting the generator output to the battery (and bus) when the generator is producing enough voltage to prevent the reverse current flow. If you watch your ammeter as you slowly advance the throttle you'll see the meter suddenly jump toward the positive side when these contacts close.

[8359]

Well after all this I wasn't able to get my current system working. And after the government shutdown I finally got verbal approval from the FSDO for the field approval of the B&C Alternator kit. Fingers crossed it'll be installed on Friday and I'll be airborne again.

I have to say I'm very impressed with B&Cs attention to detail, documentation and customer service. I'll keep you guys posted on the progress, and I'm happy to share my signed 337 if it helps anyone else in my situation.