wiring switch
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=141847
Printed Date: 02 Oct 2025 at 5:30pm
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: wiring switch
Posted By: Billy Ray
Subject: wiring switch
Date Posted: 26 Aug 2017 at 2:34pm
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I am trying to replace an unknown type of switch on my B. It has a magneto and a starter. I have purchased a universal key start ignition switch and here is where the trouble starts. The old twist type switch had no markings on the connections and had extra wires. Can someone tell me where the wires from the switch go to on the tractor? I have one labeled BAT, one is IGN , one is ACC, and the center one is unlabeled. Any help would be appreciated by this electrically challenged member.
Billy Ray
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Replies:
Posted By: tadams(OH)
Date Posted: 26 Aug 2017 at 2:36pm
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All you need to do hook it up so as you ground the wire from the mag when you want to shut the engine off.
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Posted By: DougS
Date Posted: 26 Aug 2017 at 3:24pm
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The switch will be bass-ackwards compared to how you'd wire it if you were wiring a battery ignition system. Run a wire from the Bat terminal to ground or the battery positive (I presume you haven't changed the battery to negative ground). Run a wire from the Ign terminal to the magneto. Unfortunately here's where it starts to seem odd. With the switch in the off position the tractor will be in the run mode. With the switch turned to on position the tractor will stop running. The unmarked terminal is probably designed to connect to a starter solenoid. The starter still uses the push rod to engage the start, yes?
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Posted By: Billy Ray
Date Posted: 26 Aug 2017 at 3:30pm
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Okay, more information I should have included in the first post. I have a solenoid. I also have an alternator but it only has the only wire so it is only involved in the charging process. The battery has been converted to the negative ground. This probably changed something in the wiring. Sorry about the omission earlier.
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Posted By: DougS
Date Posted: 26 Aug 2017 at 3:36pm
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Does the solenoid have one or does it have two small terminal studs?
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Posted By: Billy Ray
Date Posted: 26 Aug 2017 at 3:40pm
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it has two small studs and two big ones but the instructions with it said just use one small one but they might not know exactly what we are hooking up.
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Posted By: DougS
Date Posted: 26 Aug 2017 at 3:56pm
Use an ohm meter and make sure both studs are isolated from the solenoid frame. If both of the small studs are not, this won't work:
Run a wire from battery ground to the BAT terminal on the switch.
Run a wire from the battery hot terminal to one of the small solenoid terminals. I recommend fusing this wire near the battery. You can grab this wire from the always hot large stud on the soleniod too.
Run a wire from the other solenoid small terminal to the start terminal on the switch. I am presuming the unlabled terminal is for start.
Run a wire from the magneto to the ACC terminal on the switch.
This way will work if: The acc terminal is not connected while the switch is in the start position. A good switch should have this feature. When the engine starts you must quickly turn the switch from start to off or you will ground the magneto off. When the engine is running turning the switch to either run or acc will stop the engine.
Edit one more time... I presume you have a one wire alternator. This is really going to get complicated if not.
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Posted By: Gerald J.
Date Posted: 26 Aug 2017 at 5:28pm
That ignition switch won't work right with magneto ignition. Conventional ignition systems need 6 or 12 volts to operate as does the starter solenoid. The magneto only needs a ground to short the points to make the engine stop running.
It would be easiest to use this ignition switch to supply power to the starter solenoid and not connect it to the magneto. Connect a separate normally open push button switch to the magneto and to ground and push the button to stop the engine.
I suppose you could use a relay with its coil powered by the ignition circuit of the switch and use the normally closed contacts of the relay to short the points in the magneto when ignition power is off. Essentially reversing the operation of the ignition switch but requiring added wiring and the relay.
Gerald J.
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Posted By: Billy Ray
Date Posted: 26 Aug 2017 at 5:34pm
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Okay, forget the magneto and just tell me how to wire the switch to the solenoid . I assume the BAT switch will be to the battery and on to the solenoid. Maybe I shouldn't assume anything given my level of expertise with this stuff. Thanks,
Billy Ray
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Posted By: Gerald J.
Date Posted: 26 Aug 2017 at 8:42pm
The start terminal on the ignition switch goes to one of the small terminals on the starter solenoid and the other small terminal on the solenoid goes to ground.
Gerald J.
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