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Topic-icon No split Master Switch on this plane (only has a battery switch)

1 year 1 month ago #1095


I'm begining to instruct a gentleman in his 1967 PA-32-300. I don't know when Piper went to a split master, but this plane only has a battery switch (no alternator switch). This airplane has a 12V battery, a 60 ampere alternator and 60 ampere breaker and a 5 ampere field breaker. The 1967, POH only desrcibes the opperation of the electrical system and has no guidance regarding electrical failures.

My question is, if we had an undercharge or overcharge situation, to extend the battery life I would like the option of turning off the alternator to save 3 the ampere draw the alternator is pulling. In this situation, without the split master, to conserve battery power I think our only opption would be to pull the 60 ampere alternator breaker.

Looking at a newer 1975 Pa-32-300 POH, with split a master switch, if the alternator has no output, they recommend:
1) reducing the load, 2) check the breakers, 3) if the breakers were NOT tripped, attempt to reset the overvoltage reylay by turning the alternator switch off for one second. If these steps are ineffective, the POH recomends turning off the alternator switch, conserving power and terminate the flight.

I know I only have a basic understanding of the electrical system, but any constructive input would be appreciated.

Please forgive my spelling errors.

Thank you, Dave Wacker

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1 year 1 month ago #1104

Hi Dave;
According to my Piper expert, there should be an over voltage (OV) relay in the wiring of that '67. Which should protect the electrical system and avionics if an over voltage occurs.
Sometimes, due to a spike, the OV relay will trip. If it does the procedure to reset it is to turn off the master for a few seconds and then turn it back on. To be super safe, it's probably wise to turn off your avionics during this procedure.
If the OV relay resets, go on flying.
I don't believe you can pull the circuit breaker in this vintage Piper to take the alternator off line unless someone has upgraded the alternator CB to a pullable type.
If resetting the master switch doesn't resolve the problem, turn off the master--to avoid causing expensive OV damage to other components (avionics, light bulbs, etc)-- land when able to get the charging system repaired.

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1 year 1 month ago #1105

Thank you for you're answer Steve.

The Cheerokee is in for maintence, and they're going replace the 60 and 5 ampre breakers with pullable breakers.

Thanks again, Dave

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