Alternator Failure? 60A IR

[JonJay]

Here are my symptoms;

40 hours, Ammeter showed charging, then discharging, then charging again, etc... When charging, voltage was 14.1, when discharging 12-13. These symptoms repeated on this relatively short flight. Pulled cowling checked all wiring and plug. Nothing seemed out of sorts.

Fully charged battery overnight for trip next day. Everything checked out fine, flew to destination (45min.), all ok except after landing ammeter showed discharging during my taxi to parking. Came back to plane, taxi, run up, etc... ammeter still showed discharging. Took off to get home, after leveling out everything came back to normal and stayed that way for the rest of the flight. Landed, and while taxiing, ammeter showed discharging again.

I am curious as to others who have had alternator failures as to your symptoms. I am assuming that my regulator is going schytzo and that will be an easy first spot to look. I have gone over the posts but have found no listing of symptoms of failures.

Any help is appreciated before I change out the regulator.

[Ironflight]

Sure sounds like a loose connection to me Jon - intermittent problem like that....but that loose connection could be internal to the alternator, so if you're SURE that you don't have something in the external wiring, well....start changing parts....if it does the same thing with a new alternator or regulator, you know that's not the problem - and you'll have a hot spare on the shelf!

Paul

[MrNomad]

Two things. An external regulator can be jumped to force a load. That would eliminate the alt. By jumping the regulator, you force the alt to produce max output. That should tell you if the alt is defective.

Also, look for an intermittent short in the airplane wiring. Disconnect as much as possible and see if the pattern of charge/discharge continues. For example, if a flap motor has an intermittent short, that could be pulling an extraordinary load sending the gauge into discharge. One would expect it to blow the fuse or circuit breaker first.

Here's a way out idea. If an item in the glove box falls out onto an exposed bus, that could short. We once had to chase down a short in a van which was caused by the trailer hitch connector touching the bumper during bumps.

[L.Adamson]

When we had an intermittant problem, we made a landing at an airport, pulled the cowl, and everything looked fine.

Went ahead & tightened the alt belt just a bit more to make sure. With the engine running on the ground, everything seemed fine, but once in the air, is was discharging again.

Pulled the alternator to have it checked, when I noticed some dark gray residue on the main alt wire connection to the alternator. With a little pull, the wire came right out of the connector. It had been arching, and couldn't carry the normal load of amperage with airborne power loads.

For less than a buck, and a much better crimp, the problem was solved!

[frankh]

Confused GNS 430 and other weiredness that appeared totally unconnected.

Had to be the alt and I suspected something going on with the ground.

Sure enough dummy here had made a lovely mounting bracket and then painted it....DUH!...the paint partially isolated the alt from the engine block.

I changed to a plane power alt while I was at it which came with CAD plated braketry.

Good luck

Frank

[Build9A]

Others have already said it but....Before bailing out on your alternator, check out all the cheap stuff first. I had a similar intermittent problem and found that it was the 60amp fuse and/or a loose connection at the buss. Not sure which cause I replaced the fuse and noticed a loose connection at the same time. That's after I pulled the alternator and had it bench checked OK. Everything is fine for the past 100+ hours.

[axel howzen]

I just finished going through this. I have a B& C regulator you can go up to there web site at bandc.com. They have an excellant checklist which will start with continuity & voltage checks. I found it very helpful, you may not have their regulator but you will see what they are doing and how it will apply to your sys. I have 650 hrs on my RV. It ended up being my brushes were worn out and the slip rings were filthy.

[mike newall]

Related to this.

A discussion is going on over here about the speed that the alternator rotates at. Apparently much higher than the car application.

Here is a link

http://groups.yahoo.com/group/rvsqn/message/19268