Today's Message Index:
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1. 09:15 AM - Re: Basic question about contactors (Robert L. Nuckolls, III)
2. 10:08 AM - Re: Basic question about contactors (Alec Myers)
Message 1
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| Subject: | Re: Basic question about contactors |
At 07:27 PM 9/19/2017, you wrote:
>
>Now that I=99m looking more carefully into contactors, I=99m
getting confused.
>
>The three-terminal Ford-type contactors on my
>Cessna - that is, the battery master contactor,
>and the starter motor contactor all work by
>grounding the third terminal, so the top of the
>coil must be connected to the 12v battery terminal, internally.
When you say 'ford type' do you mean the black
plastic devices?
>The three-terminal starter contactor on my
>Luscombe has one end of the coil connected
>internally to the case (ground) and operates
>when the third terminal is connected to 12v.
This is the legacy wiring convention compatible
with off-left-right-both-start keyswitches.
>So just to make sure I=99m understanding this,
>there are two *different* kinds of three
>terminal ford-type contactors? And I guess you
>have to make sure you use the right one?
>And, surmising further, the benefit of the four
>terminal regulators is that they can sub for
>either, by connecting the second coil terminal either to ground or to 12v?
Virtually all manufacturers of contactors will
offer all variants of coil termination. Here's
a sample from the Stancor catalog on the 70/71
series devices
Emacs!
Note that all variants of coil termination are
offered.
I am surprised that your starter contactor is a ground-to-
energize circuit. I'm aware of no Cessnas that left the factory
that way . . . what year/model is your airplane?
Bob . . .
Message 2
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| Subject: | Re: Basic question about contactors |
You're absolutely right. I was misreading the mickey-mouse diagram in the PO
H. When I refer to the wiring diagrams in the service manual it's much clear
er. The starter contactor is indeed 12v-to-energize.
On Sep 20, 2017, at 12:15, Robert L. Nuckolls, III <nuckolls.bob@aeroelectri
c.com> wrote:
I am surprised that your starter contactor is a ground-to-
energize circuit. I'm aware of no Cessnas that left the factory
that way . . . what year/model is your airplane?
Bob . . .
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