I just dropped off a few friends in Marthas Vineyard (no mechanic) and went to do a run up for a quick ifr flight back to Nantucket. All of a sudden I am not getting any charge on the alternator. Is there anything I can do to check if the alternator is bad? I am getting a discharge on the ammeter, less of a discharge when radios are off, and there is no change in the ammeter reading when I pull the fuse for the alternator. Any ideas would be greatly appreciated. I carry some tools with me but have never had this problem. My other option is to fly someone over commercially from New Bedford, Ma to take a look at it.

If you could make the trip VFR, maybe no alt. wouldn't matter.

Did you check the voltage regulator mount? I was having the same issue at one time and found the regulator mount was cracked and not grounded. In a pinch, NAPA Auto Parts should have a regulator to get you to a mechanic.

Volt regulator looks fine. Not cracked. All wires are connected.

Sometimes, when an alternator goes south (bearings fail and armature contacts, shorts, to field windings) it can take the voltage regulator out with it. Being mindful of prop safety, turn prop by hand while feeling and listening to alternator. As already mentioned, okay to fly vfr, just shut down radios when not needed. But don't do that if the alternator bearings are trashed.

how can I tell if alternator bearings are shot?

I have recently been through this.

2 fried regulators later, it finally became apparent it was the alternator but we only figured that out after there wasn't enough left of the alternator to zap the reg. A bench test would have been nice, but that ain't available here. Got a brand new Plane Power now with Zeftronics reg, seems to be well built.

Watch your alternator mount, make sure that there is no play. Any looseness will cause vibration and take a new alternator out in short order. The old steel mount can be easily fixed by replacing expensive rubber bushings, the newer cast aluminum mount can also be re-bushed as long as it's not too far gone, but it is a machine shop job.

I would not be doing much flying in that "communications sensitive" part of the country with no alternator, especially with electric flaps. They eat up your battery in a real hurry then there's nothing left for one more re-start or radios.

Good luck,

GB

ington6 wrote:how can I tell if alternator bearings are shot?

Only sure way to tell is to pull the belt off and turn it by hand. It should be effortless. You'll know if the bearings are out.

Went through this recently on mine. Volt/ammeter shoed no charge, strong battery lets me finish the flight and land with what I needed to be safe (basically the radio).
First, I checked out the Cessna Pilot's Association - invaluable resource for stuff like this. Tech Note #50 talks about troubleshooting the alternator. Then I perused the forums here for info on alternators and brands.

Basic troubleshooting:
1. Checked alternator belt and tightness.
2. Checked Battery terminal connections.
3. Check all wiring connections on alternator and voltage regulator.
4. Check voltage regulator (replaced with one that was known to be good - no change, problem still exists.)
5. Check voltage at alternator terminals with Master switch on (Tech Note has step by step for this)

Conclusion - alternator not putting out voltage. Removed alternator, and did research on replacing. Looked at the Plane Power unit, gagged when I was told it was $800 for a new one (admittedly a light-weight, highly regarded replacement). I contacted the manufacturer of my alternator (National Airparts, of Lakeland, FL) to find out that they will sell me a rebuilt one, or repair mine for the princely sum of $2,150 or sell me a new one for $2,495 (neither quote included freight). Apparently the previous owner (I just bought the plane this winter) had put in the BEST alternator that money can buy (it's also on the Predator drone). I was in a local parts store talking with the tech about his offerings (only has Kelly - was warned away from that brand by many), and asked if they knew anyone that could rebuild them. Getting the "I dunno" response, another customer in the store steered me to Alaska Aircraft Engines. They took it in, diagnosed the broken brush holder (I wondered what the white ceramic pieces falling out the alternator were!) charged me an hour labor ($95), $53 for parts, and $65 for freight (fact of life here in AK). Plugged it back in, replaced the belt while I had it out, and it's worked great since.

I didn't mention that I had to drill the freakin' firewall to extract the alternator mounting bolt, but it's all good, with a new rubber grommet filling the new "access port". Two hours to get it out, 15 minutes to put it back in. I learned a lot from this little event.

Cheers,

John

Thanks guys. Was able to fiddle with some wires and get it to work for a short ferry over to new Bedford where a mechanic could look at it. Thanks for all the help. Love this place.

ington6 wrote:Thanks guys. Was able to fiddle with some wires and get it to work for a short ferry over to new Bedford where a mechanic could look at it. Thanks for all the help. Love this place.

let us know what you find

Got a brand new Plane Power now

X2 on the Plane Power recommendation if you need a new one. I researched alternators thoroughly when I built my plane. They are designed for aircraft use where most others are just car alternators used on planes. You can read up on them on their web site
http://www.plane-power.com

Does anyone know a good guy on the east coast to send out my alternator and volt regulator to? Need it tested, repaired or over hauled

We had to open my alternator up and found brushes were all dirty with black dust. Cleaned it up and it worked perfectly for 20 hours/2 months until I received replacement.