Charging issue

bahama flier

Pre-takeoff checklist
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Jan 15, 2014
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Deland, Florida
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bahama flier
I do value the vast experience of the pilots and Maintenace professionals who are very helpful with many of us who need advice on aircraft problems. I recently had my prop off for Maintenace, I put it back on after having a new alt belt, and just to be sure had my alt rebuilt. For some reason my alt will charge and then won't. I replaces my voltage regulator but it still will not continue to charge continually. I had my alt checked, 45 amps good.

New belt, alt rebuilt, new voltage regulator, what next?
 
New/rebuilt doesn't always mean it's working correctly.

What type of plane? Are you doing the work or your mechanic? Certified or experimental? DId you check the voltage regulator before replacing it or are you throwing parts at it in hopes of blindly hitting the problem?

There's a couple of excellent A&P folks on here (I'm not one of them) but more information is needed.
 
I have a Cherokee six, the alt was checked two times, 45 amps good. I did not know how to check the voltage regulator, looked over the battery wires, all seemed tight I even cleaned some to be sure.
 
The "freshly rebuilt" alternator raises flags. Who rebuilt it? Many shops put far too much grease in the rear bearing, and it squeezes out when the alternator rotor shaft goes into it. It gets flung around when the alternator spins, and gets on the brushes and slip rings and creates a resistive sludge that won't let the field current flow properly, and the alternator get weak.

Disconnect the terminals for the regulator, and put an ohhmeter between the F wire and ground. Look at the regulator to see the IASF identification on the terminals. The reading should be 3 to 5 ohms, and should remain steady when the prop is rotated. Disconnect ALL the sparkplugs first.

The intermittent thing? Maybe the regulator isn't tightly grounded to the firewall. Or a terminal on the back of the alternator is loose.
 
Your problem is intermittent. So the alternative testing good is kind of meaningless.
 
Your problem is intermittent. So the alternative testing good is kind of meaningless.
The other flag is that the alternator tested good at 45 amps. In a Cherokee Six? Shouldn't that be a 60-amp alternator?
 
Check the alternator belt tension. A loose, slipping belt can reduce alt output.

How do I know? I had an old Ford where the battery would slowly run down under high load conditions. I ended up charging down the interstate at night until the lights dimmed way down, then pulling over and letting it charge in prep for the next sprint…

The tension recommended in the book is hella tight!

-Skip
 
Intermittent problems suck. I'll sing the old refrain, check and clean the engine and airframe grounds, especially the battery to airframe. Wiggle all the crimps, maybe shoot some electric contact cleaner at suspect connections. Pipers have been known to suffer from the oft overlooked bad master switch, which can manifest in intermittent charging problems. could also be a dirty main power connection at the master bus, not really likely, but cleaning it won't hurt.Sometimes a shot of contact cleaner at the switch can work...for a while.

Finally, can you lay hands on a known good alternator to swap in?
 
The tension recommended in the book is hella tight!

-Skip
Nope. Cessna has a spec for that. Piper might, too. It's nowhere near what one would think. It involves a torque wrench on the alternator pulley and a torque reading at the point the belt slips.

At 14 volts and 60 amps it's producing 840 watts. 746 watts per hp, so a bit more than 1 hp. Even liberally allowing for alternator inefficiency we still won't need more than 2 hp. The belt need not be super tight. Overtight belts are had on the alternator's bearings.
 
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