Need help, wiring for points - The 1947 - Present Chevrolet & GMC Truck Message Board Network

lukecp · 08-01-2003, 08:25 PM

This isn't chevy truck related, but....

I am almost done re-wiring my 1952 Ford 8N tractor. The wiring was pretty hacked up by the PO who converted the tractor from 6v to 12v. I need to run a wire from the igniton switch to the coil so it can activate the points.

I hear that points need 6-9 volts to operate correctly, and 12v will burn them up pretty quick. I dont quite know how it was wired before, so it is kinda difficult to re-wire, even with a factory wiring diagram. My coil says "FOR EXTERNAL RESISTOR ONLY". So this means that the voltage going to the + terminal on the coil is supposed to already be 9v, and then the wire from the - terminal on the coil to the dizzy will also be at 9v?

I dunno how the voltage was dropped before. Can i use a internal resistor coil if such thing exists, and just feed a full 12v to the + terminal on the coil? If not, what kind or resistor is needed to drop the voltage to 9v before it is taken to the coil?

Also, the tractor has a Delco alternator which appears to be an internaly regulated model. It has 2 wires coming from it...one from the BATT terminal on the alternator, and another white wire comes out of the plug in terminal on the alternator. I hooked up the BATT wire as it was before, going to the battery cable at the starter solienoid. What does the white wire coming from the plug in terminal do? It was going to the ignition switch originally.

Thanks for any help

Class of 69 · 08-01-2003, 08:49 PM

Normally the wire to the + side of the coil would get full 12 volts for spark, and the resistor block would be wired into the - side of coil that continues on to the points. Can't help with the alt wire...sorry.

ddsmith · 08-01-2003, 10:05 PM

Actually in these trucks and similarly in many cars the resistance wire/ballast resistor is in the 12V supply to the + terminal on the coil. My 71 corvette had a ballast resistor. It is just a ceramic block with two spade terminals and a resistance coil. These trucks use a resistance wire. The ballast resistor cost three or four dollars the last time I bought one. 12V came from the ignition switch through the ballast resistor to the + of the coil. That provided the voltage drop. When the key is in the start position the + side of the coil get full 12V from one of the starter small terminals.

08-01-2003, 08:25 PM	#1
lukecp Formerly yellow72custom Join Date: May 2001 Location: Austin, TX Posts: 7,531	Need help, wiring for points This isn't chevy truck related, but.... I am almost done re-wiring my 1952 Ford 8N tractor. The wiring was pretty hacked up by the PO who converted the tractor from 6v to 12v. I need to run a wire from the igniton switch to the coil so it can activate the points. I hear that points need 6-9 volts to operate correctly, and 12v will burn them up pretty quick. I dont quite know how it was wired before, so it is kinda difficult to re-wire, even with a factory wiring diagram. My coil says "FOR EXTERNAL RESISTOR ONLY". So this means that the voltage going to the + terminal on the coil is supposed to already be 9v, and then the wire from the - terminal on the coil to the dizzy will also be at 9v? I dunno how the voltage was dropped before. Can i use a internal resistor coil if such thing exists, and just feed a full 12v to the + terminal on the coil? If not, what kind or resistor is needed to drop the voltage to 9v before it is taken to the coil? Also, the tractor has a Delco alternator which appears to be an internaly regulated model. It has 2 wires coming from it...one from the BATT terminal on the alternator, and another white wire comes out of the plug in terminal on the alternator. I hooked up the BATT wire as it was before, going to the battery cable at the starter solienoid. What does the white wire coming from the plug in terminal do? It was going to the ignition switch originally. Thanks for any help __________________ '72 Chevy C10 Mild 350/TH350/3.07. Ochre/White. Old high school ride. '70 GMC C2500 '62 327 4bbl/SM465/4.56-geared Dana 60. White/White. Project or parts truck. '97 Saturn SL DD. 1.9/5-speed. 40+ highway mpg

08-01-2003, 08:49 PM	#2
Class of 69 Registered User Join Date: Mar 2003 Location: Stillwater MN Posts: 1,166	Normally the wire to the + side of the coil would get full 12 volts for spark, and the resistor block would be wired into the - side of coil that continues on to the points. Can't help with the alt wire...sorry. __________________ 69 GMC K10 ..some restoration required....still..

08-01-2003, 10:05 PM	#3
ddsmith Glowing since 1978 Join Date: Mar 2001 Location: Lusby,MD,USA Posts: 532	Actually in these trucks and similarly in many cars the resistance wire/ballast resistor is in the 12V supply to the + terminal on the coil. My 71 corvette had a ballast resistor. It is just a ceramic block with two spade terminals and a resistance coil. These trucks use a resistance wire. The ballast resistor cost three or four dollars the last time I bought one. 12V came from the ignition switch through the ballast resistor to the + of the coil. That provided the voltage drop. When the key is in the start position the + side of the coil get full 12V from one of the starter small terminals. __________________ 66 Chevy C30 Stakebody Dump, PS,PB, 327cu in 71 Corvette Coupe 454 4 speed 69 Chevy C20 Custom Camper



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