Alternator issues

Wicked Stick · #1 04-26-2015, 02:55 PM

Im stuck here in Ocean City, KOXB, trying to troubleshoot the following.
The fuse blew for the alternator and the EFIS chimes in check volts.
I check the fuse and it was blown. This happened when I was starting the airplane. I shut down, replaced the fuse, and restarted. It was now charging at 14.2 volts. (It normally charges at 14.4). Then I noticed that the amp draw was 28 amps, with nothing really on yet I normally see just a few ampsbof draw with what I had turned on. After I taxied out and did a run up, it popped the fuse again.

Any suggestions on where to troubleshoot first ?
Does this sound like the internal Voltage regulator is shot in my Plane Power Alternator? I'm going back to the airport to put the battery charger on it for a while and pop the cowl and take a look.

Jesse · #2 04-26-2015, 03:23 PM

I assume you mean at the Alt Field fuse is blowing. Is that correct?

The amps reading is dependent on your shunt location. If you ran for a while with a failed alternator, then cranked again, it is likely that he alternator will out our high current levels for a longer period than normal while it charges the battery.

I have seen a problem just like his, if it is in fact the field breaker, when there was a loose wire on the bus either to the alternator or the battery.

C-FAH Q · #3 04-26-2015, 04:10 PM

Check the connection going into the back of the alternator for tightness, corrosion and loose or broken wires.
Speaking from experience

Wicked Stick · #4 04-27-2015, 09:05 AM

Connections all look good, 3 prong plug at the back of the alternator look clean and brand new.
all connections to battery and grounds good.
battery charged and new since 11/2014.
Put new fuse in and started a ground run.
14.4 volts, and about 15 amp output even though nothing on but efis and gps.
about 3 to 4 minutes in, alt field 5 amp fuse blows.
what's next, I'll try calling Plane Power.

DanH · #5 04-27-2015, 09:31 AM

Dave,

My initial wiring incorporated a standard blade fuse for the 60 amp Plane Power's field. It would pop infrequently and at random, usually during start, but sometimes in flight. Rewired with a circuit breaker, which has never tripped in 350 subsequent hours. I have assumed the issue is a transient operation of the crowbar function, which is designed to ground the field circuit. The breaker, being slower to trip than a fuse, ignores the momentary grounding.

If you had been previously flying with the alternator off line, I would expect the high amp output...it's just recharging the battery.

Anyway, wiring in an old breaker from somebody's junk drawer might be a safe get-home.

Re calling Plane Power, Tommy, the Hartzell telephone tech guy, is a friend, and I happen to know he is on the way home from S&F as we speak. Don't know if you can get anybody at the office. Tommy will be there tomorrow.

Wicked Stick · #6 04-27-2015, 03:23 PM

Quote:

Originally Posted by DanH

Dave,

My initial wiring incorporated a standard blade fuse for the 60 amp Plane Power's field. It would pop infrequently and at random, usually during start, but sometimes in flight. Rewired with a circuit breaker, which has never tripped in 350 subsequent hours. I have assumed the issue is a transient operation of the crowbar function, which is designed to ground the field circuit. The breaker, being slower to trip than a fuse, ignores the momentary grounding.

If you had been previously flying with the alternator off line, I would expect the high amp output...it's just recharging the battery.

Anyway, wiring in an old breaker from somebody's junk drawer might be a safe get-home.

Re calling Plane Power, Tommy, the Hartzell telephone tech guy, is a friend, and I happen to know he is on the way home from S&F as we speak. Don't know if you can get anybody at the office. Tommy will be there tomorrow.

Thanks Dan, I might try the breaker and see, but it will have to wait until I can return. Had to rent a 1 way car to get home for work.

Walt · #7 04-27-2015, 03:28 PM

Agree with Dan, normal fast-blow fuses have no place in alternator circuits, the field should be a 5A CB.

vlittle · #8 04-27-2015, 06:17 PM

I had a similar problem with my pp alternator. I started my engine on a partially discharged battery and the field cb would pop after several seconds.

I contacted pp and went through the debug procedure with no success. Eventually I pulled the alternator and made a bench test device that conclusively proved that the pp ovp was triggering at too low a voltage. A replacement of the regulator assembly fixed everything.

My hypothesis as to what happened is that using the alternator to charge a discharged main battery does two things. First, it stresses the alternator, demanding max field and armature current with minimal airflow. Second, the internal resistance of the battery allows higher voltage pulses which feeds back into the regulator/ovp circuit, triggering the ovp to trigger and blowing the fuse or cb.

Normally, this would not be a long term problem unless the ovp circuit is degraded when triggered, thereafter causing false trips and degrading further. If this is the case, it could be a fundamental characteristic of the design.

Therefore, I make it a habit of always starting the engine on a full charge. Jump starting would be a definite no-no.

Just a hypothesis, but fits the facts in both cases. If the regulator/ovp is still within spec, fully charging the battery may be a work around to this false triggering.

Wicked Stick · #9 05-02-2015, 10:48 PM

Just wanted to follow up on this thread...
This past week I purchased a new PP Alternator and changed it out at Ocean City, MD on Saturday. (Thanks again John S. for taking there)

Once I removed the old one, it was clear that a bearing and/or shaft on the back end had prematurely worn out. When I grabbed the pulley and checked for play/looseness, there was a ton of play/wiggle going on at the plug end.

I'm going to box it up and send it back to Hartzell and see what they find and if I can get some of my cost back from having to buy a new one after only 200 hours on it.

Wicked Stick · #10 05-17-2015, 04:28 PM

Quote:

Originally Posted by Wicked Stick

Just wanted to follow up on this thread...
This past week I purchased a new PP Alternator and changed it out at Ocean City, MD on Saturday. (Thanks again John S. for taking there)

Once I removed the old one, it was clear that a bearing and/or shaft on the back end had prematurely worn out. When I grabbed the pulley and checked for play/looseness, there was a ton of play/wiggle going on at the plug end.

I'm going to box it up and send it back to Hartzell and see what they find and if I can get some of my cost back from having to buy a new one after only 200 hours on it.

Following up with the reply from Hartzell's on the condition of the returned Plane Power alternator. "The slip ring bearing bore was heavily worn. This allowed the field assembly to short, which causes the field breaker to open."

Although the unit was beyond warranty (2 year warranty) and it had only accumulated 200+ hours they are willing to send me a replacement.