Planning on replacing ignition coil on my 65 c10. All stock straight six 230. No mods at all. The new coil says an external resistor is required. On existing coil I see a wire connected to positive post and one to negative post on the coil. Where would the external resistor be on a 65c10? Would there be a separate wire connecting to the coil for the resistor? Thanks in advance.
Check a wire diagram but I thought it had a resistor wire and didn't need the external resistor. But a Standard brand RU 11 will work fine.
If the wire going to the plus side of the coil is cloth wrapped it is a resistor wire so you would not need a resistor. If not it would go in line to the pos side of the coil.
Turn the ignition switch on and measure the voltage at the wire that supplies voltage to the coil. If it is 12v then you will need a ballast resistor (probably about 1.5Ω) it it is 7-9v then it has a resistor wire and you won't need a ballast resistor.
The positive side wire was cloth so that answers that question. It was mostly wrapped in tape. Truck starts now but runs rough and spits black smoke on startup. Still some other problems to troubleshoot but it's a start. Thanks for the feedback.
The wrapping was on there for the heat that would build up in the wire so if the wire looks compromised you may not want to use it for long time.
The '65 truck was a **** shoot, some had resistor wire and others have a ballast resistor. By now if it has a resistor wire it is probably shot anyway. I would just pull a fresh wire from the ignition side of the switch ( or fuse box) and run a ballast resistor. NAPA sells them and you don't have to know the resistance (although @hotroddon is probably correct @ 1.5 ohms) you just tell them what it is for and they look in the book and get the part number. Last one I bought was a 7 dollar part.
I think he was talking about the primary ignition wire from the switch not the wire from the neg on the coil. If it is not knocked down either by a resistor or by resistor wire it should always read 12V, maybe a little less under load but hopefully not much.
If the points are open the reading after the resister will read 12v a resister only knocks down voltage if there is current flow.
Yep. Now I am getting you a resistor wire would only show resistance under load. never gave that a second though actually.
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