The Ford Barn

PC/SR · 03-03-2025, 10:24 AM

A friend is putting in a new wiring harness in his '29CCPU. When he touches the hot wire to the cutout terminal he gets a spark. Is this normal? Does it indicate the cutout contacts are closed? Suggestions? Thanks PS 6 volt, positive ground, stock cutout

nkaminar · 03-03-2025, 11:33 AM

There is something wrong with the cutout. You say it is a stock cutout. Does that mean that it is the mechanical kind? If it is electronic and designed for negative ground, it will spark, and drain the battery, and may cause other problems. If it is mechanical, the points could be welded shut or there could be another problem inside. If you can,take the cover off for a peek.

ndnchf · 03-04-2025, 05:49 AM

The cutout may be installed backward. The open feet should point towards the terminal post. It is also possible that the terminal insulator is damaged or missing causing a short.

Gary WA · 03-04-2025, 12:23 PM

Quote:

Originally Posted by ndnchf

The cutout may be installed backward. The open feet should point towards the terminal post. It is also possible that the terminal insulator is damaged or missing causing a short.

washer

ndnchf · 03-04-2025, 12:49 PM

There are two insulating washers, one on each terminal screw. The thin one goes under the input side L bracket, the thick one the output terminal.

Marshall V. Daut · 03-05-2025, 12:29 PM

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It is normal for the wire to spark if it comes into contact with the metal cutout. Afterall, that wire is HOT. If you attempt to run the bolt through the wire end and attach it to the cutout, it's going to spark because you cannot avoid touching metal, either the cutout cover or the threads into the cutout. I usually disconnect a battery cable and then attach the wire to the cutout. It will not spark. Then while you watch the ammeter needle, touch the loose battery cable to its battery post. If the cable end sparks and/or you see the ammeter dip into the negative side, there is a short somewhere in the electrical system. If no spark and the ammeter remains at zero, you are ok.
Marshall

PC/SR · 03-05-2025, 08:50 PM

Thanks to all for your suggestion. Turns out the problem was not the cutout, but, a defective new stoplight switch. After checking voltage from the ammeter to the cutout, and getting spark, we disconnected the connection from the cutout to the wiring harness. No sparks, which isolates the problem to something to do with the wiring harness. After a lot of tracing of wires in the harness, disconnected the stoplight switch and no spark. Quick continuity check of the switch from the terminals to ground showed an internal short. End of problem. Lesson learned, check your new stoplight switch before installation. Thanks again

Gary WA · 03-06-2025, 02:14 PM

Quote:

Originally Posted by PC/SR

Thanks to all for your suggestion. Turns out the problem was not the cutout, but, a defective new stoplight switch. After checking voltage from the ammeter to the cutout, and getting spark, we disconnected the connection from the cutout to the wiring harness. No sparks, which isolates the problem to something to do with the wiring harness. After a lot of tracing of wires in the harness, disconnected the stoplight switch and no spark. Quick continuity check of the switch from the terminals to ground showed an internal short. End of problem. Lesson learned, check your new stoplight switch before installation. Thanks again

Job Well Done! Thanks for the update!

03-03-2025, 10:24 AM	#1
PC/SR Senior Member Join Date: May 2010 Location: Santa Rosa, CA Posts: 1,285	Cut out question A friend is putting in a new wiring harness in his '29CCPU. When he touches the hot wire to the cutout terminal he gets a spark. Is this normal? Does it indicate the cutout contacts are closed? Suggestions? Thanks PS 6 volt, positive ground, stock cutout Last edited by PC/SR; 03-03-2025 at 10:44 AM.

03-03-2025, 11:33 AM	#2
nkaminar Senior Member Join Date: Jan 2012 Location: Western North Carolina Posts: 5,860	Re: Cut out question There is something wrong with the cutout. You say it is a stock cutout. Does that mean that it is the mechanical kind? If it is electronic and designed for negative ground, it will spark, and drain the battery, and may cause other problems. If it is mechanical, the points could be welded shut or there could be another problem inside. If you can,take the cover off for a peek. __________________ A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past.

03-04-2025, 05:49 AM	#3
ndnchf Senior Member Join Date: May 2012 Location: Fredericksburg, Virginia Posts: 1,088	Re: Cut out question The cutout may be installed backward. The open feet should point towards the terminal post. It is also possible that the terminal insulator is damaged or missing causing a short.

03-05-2025, 12:29 PM	#6
Marshall V. Daut Senior Member Join Date: Apr 2011 Location: Davenport, Iowa Posts: 2,626	Re: Cut out question Sponsored Links (Register now to hide all advertisements) It is normal for the wire to spark if it comes into contact with the metal cutout. Afterall, that wire is HOT. If you attempt to run the bolt through the wire end and attach it to the cutout, it's going to spark because you cannot avoid touching metal, either the cutout cover or the threads into the cutout. I usually disconnect a battery cable and then attach the wire to the cutout. It will not spark. Then while you watch the ammeter needle, touch the loose battery cable to its battery post. If the cable end sparks and/or you see the ammeter dip into the negative side, there is a short somewhere in the electrical system. If no spark and the ammeter remains at zero, you are ok. Marshall

03-05-2025, 08:50 PM	#7
PC/SR Senior Member Join Date: May 2010 Location: Santa Rosa, CA Posts: 1,285	Re: Cut out question Thanks to all for your suggestion. Turns out the problem was not the cutout, but, a defective new stoplight switch. After checking voltage from the ammeter to the cutout, and getting spark, we disconnected the connection from the cutout to the wiring harness. No sparks, which isolates the problem to something to do with the wiring harness. After a lot of tracing of wires in the harness, disconnected the stoplight switch and no spark. Quick continuity check of the switch from the terminals to ground showed an internal short. End of problem. Lesson learned, check your new stoplight switch before installation. Thanks again