Farm Equipment - CA light switch problem

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CA light switch problem

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Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=163370
Printed Date: 10 Sep 2025 at 10:56am
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Topic: CA light switch problem

Posted By: Scott L.
Subject: CA light switch problem
Date Posted: 04 Aug 2019 at 2:43pm

I have restored a 55' CA. I am having a problem with the light/charging switch. I recently replaced it because the lights were on when in the 3rd position. It is the same with the new switch. As i understand it from the service manual, 1st position it is suppose to be low charge, 2nd position, slow charge and lights on and 3rd position fast charge and lights off. The needle moves with full range a magnet moved over it. When the battery is not even hooked up the ammeter reads 4 on the charge side.

Replies:

Posted By: DougS
Date Posted: 04 Aug 2019 at 4:50pm

It appears that something is wired wrong. I can't begin to figure out how because I'd say the 4 amps is going to the lights. The wiring is wrong somewhere other than in the switch. The ammeter shouldn't be showing anything unless a battery is connected.

Edit: The ammeter is showing 4 AMPS with the engine running, yes?

Posted By: Brian Jasper co. Ia
Date Posted: 04 Aug 2019 at 5:15pm

It's working like it should. All the way in low charge lights off. Out one notch high charge lights off. All the way out lights on high charge.

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"Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian." Henry Ford

Posted By: Gerald J.
Date Posted: 04 Aug 2019 at 6:53pm

The shop manual may help.

http://geraldj.networkiowa.com/Trees/Allis-Chalmers-G-B-C-CA-Service.pdf" rel="nofollow - http://geraldj.networkiowa.com/Trees/Allis-Chalmers-G-B-C-CA-Service.pdf

Gerald J.

Posted By: Steve in NJ
Date Posted: 05 Aug 2019 at 3:58pm

Here is how the 3 pos. switch operates:

All the way in- low charge approx. 1.5-3 amps through the resistor on the bottom of the switch. Second position- resistor is by-passed, Headlights/high charge. (the high charge is incorporated when the Headlights & Tailight or work lamp (if equipped) are on to handle the load and keep the Battery happy. Third position- High charge only, no Lights. Depending on where the third brush is located in the Gennie determines the amount of high charge. MAKE SURE THE 3 POS. SWITCH IS GROUNDED CORRECTLY! THIS SWITCH IS SELF GROUNDING, AND NEEDS TO BE GROUNDED IN THE INSTRUMENT BOX IN ORDER TO WORK CORRECTLY TO FULL FIELD THE GENNIE IN THE HIGH CHARGE POSITION. Also, the Headlight and Tailight circuits both share the "S" terminal on the 3 pos. switch. Sounds like that wire is on the wrong terminal... HTH

Steve@B&B

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39'RC, 43'WC, 48'B, 49'G, 50'WF, 65 Big 10, 67'B-110, 75'716H, 2-620's, & a Motorhead wife

Posted By: Scott L.
Date Posted: 05 Aug 2019 at 4:33pm

Thank you for your reply. Is there a special way to ground other than bolting it in.

Posted By: Steve in NJ
Date Posted: 06 Aug 2019 at 10:00am

I always tell my customers to run an aux. ground circuit off the mounting screw that holds the switch in the instrument panel to the steering post where the Pos. ground cable is normally connected. This is an added insurance which helps to make sure the switch is grounded. When folks restore these Tractors, they may paint or get some overspray into the inside of the instrument box. Paint is a great insulator of electrical grounds, so make sure the area where the switch is mounted is free of paint or rust. (make sure that the Battery ground cable has the same cleanliness) A Rolox pad on a drill works great for cleaning up the area before installing the switch. This helps eliminate non charging issues, blown fuse at the switch, & burnt resistors. The 6V system relies on its proper grounding in order to work correctly! HTH.

Steve@B&B

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39'RC, 43'WC, 48'B, 49'G, 50'WF, 65 Big 10, 67'B-110, 75'716H, 2-620's, & a Motorhead wife