---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Wed 09/20/17: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 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 _____________________________________ Time: 09:15:57 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: 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 _____________________________________ Time: 10:08:21 AM PST US From: Alec Myers Subject: Re: AeroElectric-List: 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 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 . . . ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.