resistor
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Fleet Owner
Joined: Jan 2004
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From: Brentwood,CA
resistor
does anyone know if there was a ballast resistor buillt in to the wiring in a 75 ford f-150 and do i need to add a ballast resistor when running points conversion kit which converts points to hei pickup type.
Posting Legend
Joined: Sep 2001
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The 70-74 points ignition system is listed as having a primary circuit resistor of 1.30-1.40 Ohms in my "Petersen's Big Book of Auto Repair". For 75-76 electronic ignition the primary circuit resistor is listed as the same. That book is a GREAT reference. It is not printed anymore but they are available used.
Hope this helps.
Hope this helps.
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Fleet Owner
Joined: Jan 2004
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From: Brentwood,CA
so is there a resistor or is it in the wire to the coil the crane setup said i needed resistance of 1.2 to 1.9 ohms so would this mean i don't have to add a second one and just curious where does the coil neg wire go to is it grounded or not
Posting Legend
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The resistor is part of the wire. They use a special alloy for the copper that has more resistance than std copper wire. The coil negative wire is shorted to ground by the points or the electronic ignition module. This allows current to flow thru the coil. In simple terms when the points open or the electronic module turns off a HV spark is created by the coil.
Lead Driver
Joined: Nov 2000
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From: Albuquerque
on my 77 I believe the resistor "wire" is a short jumper in a plug next to the brake booster. The purpose of the resistor is to limit the current and prevent burning out the coil, module or points.
HEI units normally use a full 12v but the stock coil probably cannot stand it for long.
HEI units normally use a full 12v but the stock coil probably cannot stand it for long.
Posting Legend
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Hmmm, they have used a resistor "wire" for about as long as I can remember. My books also list it as a wire in the harness. A short wire jumper would get red hot. Mopar uses a ceramic resistor unit and it gets very warm (it will brand you). The normal primary resistor wire gets warm in the wire bundle also. If you use a Mopar unit (0.5-0.6 Ohms) on a Ford you have to use two in series and you need to use special high temp connectors available from appliance repair shops. They use them for making connections to heating elements. If you use standard crimp connectors they will corrode and fail rapidly from the heat.
The E-coils for TFI ignition systems use straight system voltage without a ballast resistor in the wiring.
The reason a ballast resistor is used is so they can wind a coil to work well with the approx 9V available when the engine is cranking yet not overheat with full system voltage. The resistors drop the normal run voltage to the coil.
The E-coils for TFI ignition systems use straight system voltage without a ballast resistor in the wiring.
The reason a ballast resistor is used is so they can wind a coil to work well with the approx 9V available when the engine is cranking yet not overheat with full system voltage. The resistors drop the normal run voltage to the coil.
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Fleet Owner
Joined: Jan 2004
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From: Brentwood,CA
i think i should be fine with the built in resistor but i am not sure where to hook the crane cams positive wire shows i hook it up before the resistor which is not possible
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Fleet Owner
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From: Brentwood,CA
ballast resistor
i need to know where the ballast resistor is in a 75 f-150 i found something next to the brake booster it has two female prongs and there is a jumper wire connecting the two it has a resistence of 1.0 ohms is ths the resistor and if so why do i have no power going to it.but have power at the coil
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Posting Legend
Joined: Sep 2001
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You can hook up an electronic ignition box to the ignition switch or to any hot in RUN point in the fuse box. The ballast resistor is in the wiring harness. I have never seen them anywhere else in these Fords. It is a special alloy wire. I have no idea what that part is next to the brake booster from your description, but it is not the ballast resistor for the coil.
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Fleet Owner
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From: Brentwood,CA
Originally Posted by beartracks
on my 77 I believe the resistor "wire" is a short jumper in a plug next to the brake booster. The purpose of the resistor is to limit the current and prevent burning out the coil, module or points.
HEI units normally use a full 12v but the stock coil probably cannot stand it for long.
HEI units normally use a full 12v but the stock coil probably cannot stand it for long.
i found the same thing in mine what is it, it does have a resistance of 1.0 ohms
Posting Legend
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That picture is so blurry it is hard to tell exactly what it is but I would suspect it to be some bypass for a switch or some accessory that is not there anymore. Your ballast resistor is in the wiring harness.
Posting Legend
Joined: Sep 2001
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It may show up on wiring diagrams. The diagrams I have at the moment don't go back that far and the ones I have are worthless Chilton's schematics. I used to have access to those older schematics when I worked with them often. The OEM diagrams are good and it probably shows on them.
