72-73 coil ballast resistor question (1 Viewer)

[FJ40 MATT]

Hey guys I have a new coil with a internal ballast resistor in it and my old coil had a external ballast resistor in it. Was wondering if I move the other black & yellow wire that connected to the ballast resistor to the positive side of the coil now since I won’t be using it external ballast resistor. Any help would be great I just don’t want to burn the coil up and want to get this truck running. Thanks guys

 

[FJ40 MATT]

@Living in the Past would you know

 

[Living in the Past]

My understanding is the ballast resistor is bypassed while starting then used once the starter is disengauged. With a internal ballast would leave external one out of the circuit.

 

[FJ40 MATT]

My understanding is the ballast resistor is bypassed while starting then used once the starter is disengauged. With a internal ballast would leave external one out of the circuit.

Thanks, I just wasn’t sure if I should just leave the Yellow & black wire that was connected to the external ballast resistor off or connect it to the positive side of the coil instead now?

 

[Living in the Past]

Thanks, I just wasn’t sure if I should just leave the Yellow & black wire that was connected to the external ballast resistor off or connect it to the positive side of the coil instead now?

Actually the wire from the starter circuit originally wired to the same side of the ballast resistor wire going to the coil. What this did is it make a hotter spark in the spark plugs while starting. Once the starter is released at the ignition switch the ballast resistor is in the circuit. With the new coil you have you will wire both wires to the coil and the ballast resistor will always be in the circuit even when starting. Keeping the circuit resistor in the circuit you will end up with two ballast resistors in series. This will cause a weaker than designed spark.

 

[FJ40 MATT]

Actually the wire from the starter circuit originally wired to the same side of the ballast resistor wire going to the coil. What this did is it make a hotter spark in the spark plugs while starting. Once the starter is released at the ignition switch the ballast resistor is in the circuit. With the new coil you have you will wire both wires to the coil and the ballast resistor will always be in the circuit even when starting. Keeping the circuit resistor in the circuit you will end up with two ballast resistors in series. This will cause a weaker than designed spark.

Thanks again for your help. Just so I’m understanding what your saying is that I’m just going to take the black
& yellow harness wire off the external resistor and put it on the positive side of the coil since the resistor is internal on the new coil. I understand i don’t want two Resistors I just wanted to make sure I put the yellow & black wire onto the right side of the coil

 

[Living in the Past]

I see a bunch of extra wires in your picture. I looked my 2/73 FST. The coil is missing but the ballast is there but can tell how it was wired. From the three wire harness the plain black wire goes to negative post on the coil. Black with yellow tag goes to one side of the ballast. Other side has a small jumper that goes to the positive post on the coil. The black wire with a white tag along goes with the jumper on the positive post on the coil. My Haynes manual doesn't show the US having the ballast but 74 wiring diagram shows the ballast wired that way. The rest of your wiring does not look stock and should be traced why it goes and what it does.

Here is the nightmare my 73 FST wiring. The ballast is there just lose on top of the fender why the coil mounts.

 

[FJ40 MATT]

I see a bunch of extra wires in your picture. I looked my 2/73 FST. The coil is missing but the ballast is there but can tell how it was wired. From the three wire harness the plain black wire goes to negative post on the coil. Black with yellow tag goes to one side of the ballast. Other side has a small jumper that goes to the positive post on the coil. The black wire with a white tag along goes with the jumper on the positive post on the coil. My Haynes manual doesn't show the US having the ballast but 74 wiring diagram shows the ballast wired that way. The rest of your wiring does not look stock and should be traced why it goes and what it does.

Here is the nightmare my 73 FST wiring. The ballast is there just lose on top of the fender why the coil mounts.
View attachment 2560897

Thanks for your help, I’m just going to go to Napa tomorrow and buy the right coil and external ballast resistor and wire it back up the same way it was.