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64C Electrical Issue


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64C. Troubleshooting an electrical issue. 12v system. This morning had barely enough juice to turn the prop (took ~5 minutes of trying to start the motor). After everything came online, noticed that the alternator only showed 13.1v when it normally shows 14v. Power gradually dropped to 11v and popped the circuit breaker. Shut down and called a mech buddy.

30 minutes later he measured the battery prior to start, showed nominal 12v. He also measured the draw on the battery during engine start. Only dropped to ~11v and plane started right up. However still lower than normal volts with alternator online, and power eventually dropped and popped the circuit breaker again.

It was a pretty cold night last night and it was the first frost of the season. The plane is temporarily parked outside. Also just changed the starter with an overhauled model of the one I previously had. Flew fine yesterday during post maintenance test flight, however noticeably less torque during engine start. Also had a decent amount of moisture get in the cockpit during recent storms. Had to use DampRid to get the moisture out.

Bad battery? Bad alternator? Resistance on the overhauled starter? Effects of moisture in the cockpit? Any ideas?

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Sounds like...

1) Suspect new starter...

2) If current isn’t getting all the way to the starter... it may be grounding out somewhere else...

3) It seems as though electricity is going somewhere else, since a breaker tripped...

4) If that is the starter’s breaker... check its external wires for any frays or exposed wires... and any marks of welding in process...

5) could also be internal wiring of the new starter... ?

PP thoughts only, not as sharp as the other knives in the draw...

Best regards,

-a-

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3 hours ago, Matt Lindeman said:

The GEN circuit breaker. However, the generator was replaced with an alternator in 2013.

If the breaker is appropriately rated, the alternator should not be capable of putting out enough current to trip this breaker. The purpose if the breaker is to protect against a fault in the alternator or it’s wiring. It sounds like maybe current was flowing back through the alternator. Was the ammeter showing a heavy discharge when the voltage dropped?

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The thing that jumps out at me is 13V after start. Should be more than that to charge the battery well.

I would get a voltmeter out to verify that 13V figure with the engine running and if so be looking at your charging system. Alternator & voltage regulator..... or what parts of it might have been inadvertently touched/messed with with your new starter install?

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