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Re: Alternator Field Switch
Originally Posted by
CTJER
In reply to SMO22; yes master is traditional under seat DPDT.
Chris my understanding is that with the field off, the drag on the starter will be reduced during start....
Jeff, what do you men by "generator switch" ? I don't see one in the Colt electrical schematic. Are you referring to the generator CB?
Jerry
The engine is actually running before an alternator starts producing power and creating a drag. If I recall correctly the rpm required is between 500 and 700. An alternator will fall offline if you can get the engine to idle slow enough.
It had to have a generator switch if it was a conversion. Possibly in conjunction with the master switch. I have not worked or flown a Colt so I don’t know the original switch configuration but my Pacer had a 3 way toggle under the seat. I think up was battery and generator, center was off and down was battery only.
Steve and I use the same switch.
Last edited by Jeff J; 01-18-2019 at 11:58 AM.
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Re: Alternator Field Switch
At one point in my working life I had to develop processes to remanufacture alternators. The finished alternators were run a test bench. One of the checks was “turn on rpm”. They don’t turn on immediately but once on they will generate voltage at a lower rpm then the turn on rpm. Turn on rpm is higher than what the starter can turn the engine over.
My 31 Ford pickup idles about 450 rpm. Once started I have to rev it once to turn my retro fitted Delco alternator. Once on it will usually keep producing power at idle.
Last edited by Gilbert Pierce; 01-18-2019 at 04:29 PM.
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Re: Alternator Field Switch
the Jacobs on my 195 is similar, need to get it to 1000 rpm or a little over then it will stay
on down to 650 to 700 during warm up. No I have an idea why. Thanks Gilbert
"Progress is our most important problem"
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Re: Alternator Field Switch
Originally Posted by
CTJER
I have the InterAV alternator installed. No Field Switch that I can find. The Installation Instruction Schematic shows "original field switch". The AC electrical schematic shows nothing like this. Is such a switch required? If so can someone recommend a part number and wire size?
Jerry
Originally Posted by
CTJER
In reply to SMO22; yes master is traditional under seat DPDT.
Jerry
Original field switch, have you looked at it to see if the original generator field pole on your DPDT master is connected to your alternator field wire? If you have a DPDT master than that was how your generator was wired, one pole connected battery to buss, other pole closed the generator's own 12 volt field circuit to tell the generator to turn on. Does the alternator stay on when you turn the master switch off? If it turns off than you know the DPDT master is also your alternater field switch
Originally Posted by
Jeff J
It had to have a generator switch if it was a conversion. Possibly in conjunction with the master switch. I have not worked or flown a Colt so I don’t know the original switch configuration but my Pacer had a 3 way toggle under the seat. I think up was battery and generator, center was off and down was battery only.
I thought the DPDT masters were battery and generator both on in either ON selected position. Did Piper wire them with battery only in one ON position?
I've seen alternators wired like that.
If Jerry's alternator is using the original generator's field switch (DPDT master possibly?)
If it is, I am curious which way they put 12 volts on the generator's old field pole of that DPDT master? Is this in the STC?
Last edited by SMO22; 01-18-2019 at 07:17 PM.
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Administrator
Re: Alternator Field Switch
Originally Posted by
SMO22
Original field switch, have you looked at it to see if the original generator field pole on your DPDT master is connected to your alternator field wire? If you have a DPDT master than that was how your generator was wired, one pole connected battery to buss, other pole closed the generator's own 12 volt field circuit to tell the generator to turn on. Does the alternator stay on when you turn the master switch off? If it turns off than you know the DPDT master is also your alternater field switch
I thought the DPDT masters were battery and generator both on in either ON selected position. Did Piper wire them with battery only in one ON position?
I've seen alternators wired like that.
If Jerry's alternator is using the original generator's field switch (DPDT master possibly?)
If it is, I am curious which way they put 12 volts on the generator's old field pole of that DPDT master? Is this in the STC?
I installed a few alternators recently and removed the wire from the DPDT switch and installed it to the 5 amp CB switch. I guess you could use a CB and retain that switch and be a simple install.
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Re: Alternator Field Switch
Originally Posted by
Steve Pierce
I installed a few alternators recently and removed the wire from the DPDT switch and installed it to the 5 amp CB switch. I guess you could use a CB and retain that switch and be a simple install.
That's exactly what I'm wondering, if they used a five amp circuit breaker from the bus and ran that to the old generator field pole on the master.
Last edited by SMO22; 01-18-2019 at 07:35 PM.
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Administrator
Re: Alternator Field Switch
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Re: Alternator Field Switch
Originally Posted by
SMO22
I thought the DPDT masters were battery and generator both on in either ON selected position. Did Piper wire them with battery only in one ON position?
I think you are correct for most installations. It's been nearly 20 years since I did the conversion so some of the details are lost to time but I think mine was wired more like the lined out diagram on drawing 12629 when I started the conversion.
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Re: Alternator Field Switch
If I recall correctly there is a circuit breaker, perhaps 5 amp called out for the field circuit.
I used a 5 amp circuit breaker switch to be able to turn off the alternator.
I believe there should be a placard that says:
> This Aircraft is alternator equipped <
Turn off field circuit switch(generator switch)
before opening circuit breaker or turning off battery master switch.
Do not run engine, operating alternator without battery connected in circuit.
So yes Virginia, there is a Field Switch
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Re: Alternator Field Switch
When it is real cold, turn alternator field off to reduce drag on the start up. Increases chance of starting in marginal startup situations. Similar to switching to left mag only.
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