Alternator Question

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FlyingJack2
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Joined: Sat Feb 02, 2013 11:44 pm

Alternator Question

Post by FlyingJack2 »

Recently purchased a 170B with an alternator, and I have a couple of questions for the electrical gurus. I've searched through several threads and don't see the questions addressed, so forgive me if these has been asked and answered.

1.) When should the alternator switch be placed ON? Prior to engine start, after start, or does it matter?

2.) When should the switch be place OFF during the shutdown sequence or does it matter? I'm currently turning off all the radios, shutting the engine down, and then turning the alternator to OFF.

Thanks for your replies.
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lowNslow
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Joined: Mon Apr 22, 2002 4:20 pm

Re: Alternator Question

Post by lowNslow »

Most early installations have a regular 2 amp circuit breaker on the field circuit, it sounds like you have a circuit break switch instead. The later installations have the double rocker switch which control the field and master power. I think you would be safe to leave it on if is in fact a circuit breaker switch and not just a switch (i.e. you should have 2amp protection on the field circuit).
Karl
'53 170B N3158B SN:25400
ASW-20BL
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Bill Hart
Posts: 455
Joined: Tue Aug 23, 2005 2:04 pm

Re: Alternator Question

Post by Bill Hart »

I will turn the field switch on after the engine is running and open the field prior to shut down. If you don't have a raido switch make sure you have all of your electrical items off before you turn the field on and off.
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GAHorn
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Re: Alternator Question

Post by GAHorn »

I'm in the "doesn't matter" camp. (I'd turn 'em on/off simultaneously. The only reason to have them switched seperately is in order to continue essential electrical operations (such as fuel pumps, radios, flaps, lighting, etc.) with Master ON should the alternator fail, in which case the alternator would be switched OFF.)
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
HA
Posts: 353
Joined: Thu Jan 20, 2005 11:41 pm

Re: Alternator Question

Post by HA »

turn it on and off when there's no load, even though I think the normal coupling for these installations isn't the "elastomeric" type that is supposed to break loose to prevent gear damage in case of an alternator seizing. Our company has several Senecas with alternators with that type coupling and I teach the guys to never touch the alternator switches, just leave them on always. If you switch off the alternator when there's a good electrical load on it it'll jerk a bit and that's when you lose those breakaway couplings.

I think you'll have the regular type coupling like is used with the generators, and that is more robust. But it's easier on things if you just go on-off with no loads.
'56 "C170 and change"
'52 Packard 200
'68 Arctic Cat P12 Panther
"He's a menace to everything in the air. Yes, birds too." - Airplane
T. C. Downey
Posts: 548
Joined: Sat Jan 26, 2013 5:58 am

Re: Alternator Question

Post by T. C. Downey »

I turn it on after the engine is running, I like to see the Amp meter go from - to +
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