Lately I've noticed that it takes a brief rpm increase to about 1800 to get my alternator to output. The other day I noticed in flight around 2400 rpm that my battery was discharging. I changed rpm as much as I could in level cruise and no dice. So I landed and it started charging again.

I checked my wiring and found and fixed a loose connector this weekend when I changed my oil, but then on my leak check it requires an rpm increase to start charging again.

What should I look at next in troubleshooting? Does this sound like something you might have seen before?

I have spent many hours trouble shooting charging issues. Each time it usually results in this order ( but, not exclusively) resulting in several cumulative faults...

Order of testing and replacement ( I believe I'm have replace every item at least once):

* Wires and crimps (vibration takes its toll)

* Voltage regulator

* Relays

* Master/alternator online switches

* Alternator bearings/ brushes. / diodes (external rectifier)

* Charging instrumentation amp/voltmeter

* Bad house battery

* battery temperature sensors

* slipping belts (Lycoming)

Very common. Little airplanes are pretty simple and cheap. No start generator, no standby generator, no AC, no APU, no customer bleed air, no Herman Nelson, etc. Pretty safe to assume no radio or lights.

Cam,

First place I'd look is for a bad ground connection.

MTV

I'll recheck all the wires to and from the alt and then start digging into grounds. Hopefully it's a wiring issue and not the alt itself, I think blackrock's alternator has already sold!

Belt looked good but I didn't check the tension. I'll look at that but I'd figure it would be toast by now if it was loose enough to slip.

Check the jumpers around engine mount bushings and firewall bushings if you ground through the engine mount. Or add a ground strap direct to the engine.

Two places to definitely check the ground: 1) The ground strap at the battery itself, the single most likely place for corrosion that can stop recharging in its tracks. Check both ends, at the battery and at the airframe. 2) The ground strap between the engine and the airframe. Engine vibration is the culprit there.

Keep in mind that you won't likely find anything loose. You'll need to take off the connections, buff them, and reconnect them. You'll be surprised at how much better everything electrical will work.

Cary

I forgot about the grounding strap ( engine to airframe).

The ground path melted a throttle cable inoperable twice here in Hawaii! The strap was missing. Very very very dangerous!!!

CamTom12 wrote:I'll recheck all the wires to and from the alt and then start digging into grounds. Hopefully it's a wiring issue and not the alt itself, I think blackrock's alternator has already sold!

Belt looked good but I didn't check the tension. I'll look at that but I'd figure it would be toast by now if it was loose enough to slip.

I agree with all the above points to check out, especially wire connections and grounds.

Mine is still for sale, all the details are in the listing:

http://www.ebay.com/itm/331651819244?item=331651819244&viewitem=&sspagename=ADME:L:LCA:MOTORS:1123&vxp=mtr

and as of now, there are no bids on it. If you think you might want it, let me know and I'll cancel the EBay listing and will make you a great deal on it. Money back guarantee, too. This is a really nice, solid unit and is internally regulated. If yours is externally regulated, you could remove the regulator and save some weight.

Can I get back to you this evening? I'll take a trip out there to double check grounds and do another ground run after work.

CamTom12 wrote:Can I get back to you this evening? I'll take a trip out there to double check grounds and do another ground run after work.

Sure, no rush on my end. You might even want to take yours off the plane and take it to a local alternator shop if you can find one. They can run it on there test stand to see if there are any problems with the alternator. It may just need brushes or something like that. Don't tell them it's off an airplane, though!

I checked all wires, they're snug now. I tightened the belt a bit, but it wasn't excessively loose. It's grounded through the frame, but I didn't have extra wire to slap a temporary ground on it to check that. I have no noise in my ICS, so I don't know if that's a good indication of a ground.

Had the same initial condition on a ground run: no output until I ran the engine up to about 1500 rpm, then it charged the battery at all rpm.

Here's the alternator in question:





Look familiar to anyone?

It could also be brushes in the alternator. I once had worn brushes that exhibited intermittent symptoms like this. They were worn down, and the springs weren't compressed as much as they should have been. Certain RPM ranges would cause them to lose contact with the commutator.

Complicating the diagnosis was that it was on an O-470 Continental, which turns the alternator backward. On an automotive tester, it checked out good. It turned forward, like it should for automotive, and the change in rotation caused the brushes to dig in a bit, masking the problem!

As others have said, check the ground path. It's often not given enough consideration, particularly from the engine to airframe.

PM sent.

I'll put my money on the brushes. Swap it out for a new or rebuild alternator.

What's TT on the brushes?

I just went thru this. My alternator was intermittent like yours.. I found this video very helpful.. I trouble shot it in 10 min and replaced the alternator with a Plane Power Alternator.

I think watching the video took longer than the trouble shooting and Alternator replacement.

Wish I had done it years earlier..

http://www.eaavideo.org/video.aspx?v=1549006054001

Good luck!

Scott

~105 hours on the alternator to my knowledge. That's the total time on every other component on the airplane. I'm willing to bet its the brushes as well. George, I'll also be replacing with a plane power, courtesy of Mike. He made me a screaming deal on his and has offered excellent advice for wiring the pigtail and the connectors and crimper that worked best for him. I'm going to order the stuff he recommended this morning!