C Charging System
Printed From: Unofficial Allis
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=180370
Printed Date: 16 Dec 2025 at 11:27pm
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: C Charging System
Posted By: Barry
Subject: C Charging System
Date Posted: 06 May 2021 at 2:53pm
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When I started her this spring the ammeter showed little to no charge, and did not change when the light switch was pulled either part way or all the way out. Lights didn't work either. Checked lights by putting 6V directly to the common junction and they do indeed work. Ammeter "vibrates" , but little to no charge. I put a new light switch in but no change. Shorted the field winding on the generator and ammeter showed charge, but meter "vibrated". Took cover off the cutout and saw the contact made and broke rapidly, probably the reason for the ammeter "vibration". When I manually closed the cutout contact there was no charge on the ammeter. Do I have a bad cutout? If not, any ideas? Thanks.
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Replies:
Posted By: steve(ill)
Date Posted: 06 May 2021 at 4:56pm
when you ground out the FIELD terminal, you are bypassing the LIGHT SWITCH.. Your wire to the switch is bad, or the switch case is not grounded to the frame... The CUTOUT is on the GEN (Armature) terminal and is the HOT side to the amp meter.
 ------------- Like them all, but love the "B"s. |
Posted By: Barry
Date Posted: 06 May 2021 at 5:59pm
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Thanks. I'll double check the wiring again and the ground. Do those possibilities explain why the relay contacts open and close rapidly? That rapid opening and closing doesn't always happen. Sometimes the contacts stay open when the engine is running. |
Posted By: steve(ill)
Date Posted: 06 May 2021 at 6:45pm
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the OPEN or CLOSE depends on if the battery voltage is higher than the generator output voltage... it should OPEN when the motor stops and the generator has no output.. Without a good ground, it might look real abnormal.
when you closed the contact manually, there was no output because you have no ground... Ground the "F with your jumper and you will see the contact close and battery start charging. ------------- Like them all, but love the "B"s. |
Posted By: steve(ill)
Date Posted: 06 May 2021 at 6:50pm
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notice in the picture above the light switch case is GROUNDED to complete the circuit back to the battery.. Common on old tractors to have rust under mounting bolts and not have a good ground.. Clean the mounts, or run a seperate wire from the light case to a good ground / or battery.
------------- Like them all, but love the "B"s. |
Posted By: Steve in NJ
Date Posted: 07 May 2021 at 7:01am
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The cutout has nothing to do with charging. All the cutouts function is to sever the Battery from the Generator so when the Tractor sits, the Generator doesn't act like a Dynamo and drain the Battery. HTH Steve@B&B ------------- 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: Barry
Date Posted: 07 May 2021 at 9:14am
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Well, I checked the light switch ground by checking continuity between the switch stem outside the box to the battery cable ground connection at the steering post. That was good. Then checked the continuity between the generator field terminal and light switch resistor terminal. It was good, checked both the wire when disconnected from the field terminal, and the terminal itself with wire connected. Both good. When I grounded the field terminal on the generator I did get charge, but the cutout kept making and breaking rapidly. Still wondering about the cutout. should I be checking some grounding of the cutout, or some other ground? Thanks for any help you guys can give me. I'm a mechanical engineer who wishes he paid more attention in his electrical courses.
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Posted By: steve(ill)
Date Posted: 07 May 2021 at 9:34am
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the cutout closes when the GENERATOR puts out more voltage than the BATTERY (IE.. tractor running)... The CUTOUT will open if the wires are corroded, generator voltage output is low, light switch bad.. If you want to check your cutout, just jumper around it when running ( "A" terminal to battery terminal) .............. BUT... you already said when you ground the "F" it starts to charge ??? Could be the generator is weak... Put a volt meter on the "A" and Ground and see that you have 6.5 volts ( battery) with the tractor OFF... and over 7 volts when running.. IF not, the Generator is not working properly.
------------- Like them all, but love the "B"s. |
Posted By: steve(ill)
Date Posted: 07 May 2021 at 9:35am
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still question in the light switch ( second problem ?) if you can ground the "F" and get things to work " sometime". ------------- Like them all, but love the "B"s. |
Posted By: fleeter allis fan
Date Posted: 07 May 2021 at 9:11pm
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As mentioned, grounds on old tractors can be a problem. Even if it tests good with a meter, you can have a high resistance connection. I would check and clean every ground and every connection, in case something corroded during winter storage. My B caused me grief because the battery ground to the steering column support was bad. That support is threaded into the torque tube and I guess it was corroded enough at that threaded joint to prevent a good ground. I moved the ground directly to the frame to solve the problem. ------------- I'm a man...and I can change...if I have to... I guess. '44 B, '46 WF, '49 G, 810GT, 916H, 620 |