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Burning through ignition coils

27K views 59 replies 9 participants last post by  2old2fast 
#1 ·
1977 Ford LTD
351M

I have been burning through ignition coils since I bought this car a couple years ago. They overheat and it only happens during the summer. If I leave the AC on with the car in idle the coil is sure to overheat,

It is probably note worthy to say that the car purrs with the A/C off, but when it is on the car runs horribly. In fact it is difficult to even start the car if the AC is on, but if the A/C is off the car fires right up. I converted the A/C to R134 and replaced everything but the hoses. That had no effect on the running or starting what so ever

Last thing is I increased the timing from four degrees behind TDC to TDC. I replaced the carb also, no difference.

Any ideas?

Thanks!
Any ideas?
 
#52 ·
oldred said:
There is no need to remove the resistor wire since this requires opening the harness and can be intimidating to someone not familiar with wiring. Simply splice into the Red/Green ignition wire at the switch and run the new wire to the resistor then the coil, clip the end of the old wire at the coil and tape the it safely into the harness then any factory wiring failures will be effectively by-passed, I have repaired a couple of resistor failures this way.
This is true, I just don't like leaving stuff that may cause questions later.He is going to have to run a new wire anyway so why not remove the old one.
 
#53 ·
There is no reason for it to cause problems later because it will no longer be connected to anything, that's why I said to tape it safely into the harness. Leaving the resistor wire in place does not affect anything once it is removed from the coil but attempting to locate it in the harness and then removing it can cause problems since it is only one of several wires that are spliced into the main (Red/Green) wire from the ignition switch, this wire also powers the control module. Sometimes removing the resistor wire is fairly easy and other times it can be a huge undertaking and not a good project for someone unfamiliar with wiring, by-passing it is simple.
 
#59 ·
Steven Pisonero said:
I will disconnect. I have ran the bypass. I am getting the full 14V before the resistor. In the run position I am getting 7V and while the car is idling I am getting 9.8 - 10. Is this correct> I am going to put a 15V inline fuse in.
Fuses are rated in amps not volts. If you do fuse it put the fuse as close to the source as possible. A 10-15 amp fuse would probably be sufficient. If you have an amp meter, check the draw on the circuit and go about 20% over.
 
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