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One Wire Alternator [message #370371]

Wed, 17 August 2022 10:26

Tom Katzenberger

Messages: 399
Registered: June 2019
Location: Kingsville, MD

Karma: 4

Senior Member

Guys,

Was the one wire alternator used on all model years? I pulled an alternator off of a 1977 that had the one red (Pos) post, but also had a small black post next to the red post. I wasn't sure if this small black post was in fact a negative post or was there for a guage?

If anyone knows if this is OEM or replaced by a PO.

Thanks and have a great day,
Tom K.

Tom & Oki Katzenberger, Kingsville, Maryland, 1977 23' Birchaven, 455 C.I.D., Micro Level, Howell EBL-EFI Spark Control, Macerator, York Air Compressor, 6 Wheel Disc, Quadra Bag, Onan W/Bovee Ignition

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Re: One Wire Alternator [message #370372 is a reply to message #370371]

Wed, 17 August 2022 10:52

Keith V

Messages: 2337
Registered: March 2008
Location: Mounds View,MN

Karma: 0

Senior Member

Not OEM, Not recommended.

Keith Vasilakes
Mounds View. MN
75 ex Royale GMC
ask me about MicroLevel
Cell, 763-732-3419
My427v8@hotmail.com

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Re: One Wire Alternator [message #370373 is a reply to message #370371]

Wed, 17 August 2022 11:40

lqqkatjon

Messages: 2324
Registered: October 2010
Location: St. Cloud, MN

Karma: 5

Senior Member

You can search and read lots of opinions on the “one wire” alternator. It is not a stock item.

I always thought this is exactly why one should not bother…. Now you have a coach that has a different alternator the. Stock and the owner has no documentation on why it is there and how it should be wired. Not in the books.

Jon Roche 75 palm beach EBL EFI, manny headers, Micro Level, rebuilt most of coach now. St. Cloud, MN http://lqqkatjon.blogspot.com/

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Re: One Wire Alternator [message #370375 is a reply to message #370372]

Wed, 17 August 2022 11:52

Ken Burton

Messages: 10030
Registered: January 2004
Location: Hebron, Indiana

Karma: 10

Senior Member

To my knowledge there was never a one wire alternator used on any GMC.

There was an offering of a 140 amp alternator offered in 1978 transmode. I saw one once on a 403 that we pulled out of a 1978 airport people mover. I was not interested in it at the time and we just pulled the engine and installed the 403 with the 140 amp alternator in a 197x Birchaven. It might have been a 1 wire setup. I don't remember.

You definitely to not want a one wire one, especially if you have the OEM isolator installed.

Ken B. .

Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

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Re: One Wire Alternator [message #370377 is a reply to message #370371]

Wed, 17 August 2022 13:58

Tom Katzenberger

Messages: 399
Registered: June 2019
Location: Kingsville, MD

Karma: 4

Senior Member

Thanks guys,

I will look for another Back up Alternator.

Thanks guys,
Tom K.

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Re: One Wire Alternator [message #370379 is a reply to message #370377]

Wed, 17 August 2022 14:26

Matt Colie

Messages: 8547
Registered: March 2007
Location: S.E. Michigan

Karma: 7

Senior Member

Tom Katzenberger wrote on Wed, 17 August 2022 14:58

Thanks guys,
I will look for another Back up Alternator.
Thanks guys,
Tom K.

Tom,

If you get stuck, I think I have a spare 27SI small frame. (That 27SI came in both small and large frame - dumb idea)
If you are looking for one, contact a rebuilder and tell him you need a Delco 27SI with remote excitation. They were really pretty common and the difference is only the regulator part number. The remote sense/excitation was used on all the big things, but not on many passcar.

Matt

Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit

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Re: One Wire Alternator [message #370383 is a reply to message #370371]

Wed, 17 August 2022 15:10

jhbridges

Messages: 8412
Registered: May 2011
Location: Braselton ga

Karma: -74

Senior Member

To clarify, if you have an isolator and house batteries as well as chassis battery (OEM setup) the single wire alternator will never fully charge the batteries due to the drop across the isolator. The OEM remote sense wire cures this problem by sensing voltage at the battery and turning the alternator up enough to accomplish full charge. The difference isn't much, but will shorten battery life a bit. Go for the OEM setup.

--johnny

Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons. Braselton, Ga. I forgive them all, save those who hurt the dogs. They must answer to me in hell

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Re: One Wire Alternator [message #370384 is a reply to message #370371]

Thu, 18 August 2022 08:25

Tom Katzenberger

Messages: 399
Registered: June 2019
Location: Kingsville, MD

Karma: 4

Senior Member

Thank you guys,

Matt, Thank you for the offer, I have some spare alternators around here. One has the double spade plug fitting and a positive post, but it also has a very small post with a black insulator at the post base going through the housing adjacent to the positive post. This small post is not threaded. It looks like a push on connector goes on it. Perhaps an AMP meter or gauge connection?

It came out of a GMC motorhome. I just don't know what that small post is for?

Thank you for sharing you thoughts, I appreciate everyone's help.

Take care,
Tom K.

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