Farm Equipment - Burning up coils On my AC-b

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Burning up coils On my AC-b

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=196452
Printed Date: 12 Oct 2025 at 8:03am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com

Topic: Burning up coils On my AC-b

Posted By: LBOW
Subject: Burning up coils On my AC-b
Date Posted: 02 Aug 2023 at 3:22pm

Just wondering what would make 2 wico x coils go bad in a short amount of time, I wasn't running it very hard, but I was starting and stopping a lot. Second coil didn't even last a day. I have a distributor setup from a CA, I think I'll try running that instead but I'm curious why a coil would fail so quickly... Thanks

Replies:

Posted By: Ken Mn
Date Posted: 02 Aug 2023 at 3:32pm

LBOW: Using Wico coils, does that mean you are running a magneto?

Posted By: LBOW
Date Posted: 02 Aug 2023 at 3:49pm

Yes, wico x magneto... ran great for a long time, now I'm afraid to order another coil... (Actually a prestolite)

Posted By: Ken Mn
Date Posted: 02 Aug 2023 at 4:48pm

As long as you do not have any battery power connected to your magneto you are not burning up the coil. I have heard though that resistor spark plug wires are bad. They must be wire type and do not gap the spark plugs wider than spec. Doing so requires the coil to have to build up the voltage higher than normal before the plugs fire and that can cause the insulation in the coil to break down and short out ruining the coil.

Posted By: LBOW
Date Posted: 02 Aug 2023 at 5:10pm

Thanks.
The wires and plugs are correct but could it have anything to do with the condenser spiking the voltage...? I never did change it out. And as I was working on the hydraulics I was crank starting it a lot... No battery

Posted By: Ken Mn
Date Posted: 02 Aug 2023 at 6:49pm

The condenser won't cause a coil to fail.

Posted By: HudCo
Date Posted: 02 Aug 2023 at 10:56pm

make sure your kill wire is not getting battery voltage some how

Posted By: JC-WI
Date Posted: 02 Aug 2023 at 11:45pm

Same thought I had...

"make sure your kill wire is not getting battery voltage some how "

Or shorting out before the kill switch. Disconnecting the grounding wire and still no spark, that is a puzzle unless there's dirt or corrosion in the points... or bad grounding of the points... or of the coil.

Magnets strong?

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