Well this is my 2nd thread today, iv been working on my truck over the weekend. I walked outside today and seen smoke come outa the engine. So i popped the hood and seen the coil blew up. I thought it was a bad coil so i went to buy a new coil and installed it. No the key was not left on. Then not a half hour later the new coil blew up again! So i returned it for a new one, and i also bought a new ignition switch and lock cylinder. I disconnected the battery put in the new coil and ignition system. So now i connected the battery and 1 min later the coil was already getting hot! I disconnected the battery, and i disconnected all the wires from the ignition switch. Connected the battery and 1 min later the coil is hot again. Im probably going to have to take in to a mechanic, but not before i asked you guys. The truck is a 1966 f250 with a 352. Also when i put the battery cable back on the battery it sorta sparks. But when i take the positive and negaitive wires off the coil the battery does not spark when i put the battery cable back on.

 

First thought is a short, but with the switch off, could the coil be connected to the wrong side of the starter relay?

 

Ok i swapped the front wires on the relay with the battery cable on and after 5 mins the coil di not heat up. Then i tried starting the truck up and no ignition. So i swapped the wires on the relay back to what they were, and one of the wires as i put it on the relay sparked. I put the battery cable back on and the cable did not spark as i put it on the battery. And so far so good. It seems like when the relay wire sparked that somehow stopped the battery cable from sparking, and currently everthing is working, we even started the truck up and ran it for a while.

 

I would measure the voltage being applied to the coil. What would cause a coil to blow up so to speak?

D

 

I'm a process of elimination guy. If it happens again, I would look at replacing the starter relay. Good luck

 

+ from switch


- to distributor


check voltage and make sure the coil is grounded good
mine would not work once due to some corrosion in the bracket
cleaned bracket and got spark

 

We have the wire from the distributor to the -neg side of the coil. And the coil is in the round metal bracket. All connections are good. Is there another ground?

 

no electrician but, I had a truck that had sit for some time


my coil had 12 volts in on the + side with nothing on the neg side
the coil brkt was loose and had some rust around it
I removed the coil, cleaned and tightened
the truck fired right up