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From: I'd like to propose a toast... to internal combustion and wind in the face.
Originally Posted by MelWff
you need to use a voltmeter but would expect bulbs to burn out and I thought it was already established you are missing the resistor wire. Have you looked at the points to see if they are burnt?
I started tearing the ignition system apart before doing any electrical diagnostic testing. Visual inspections haven't revealed any burnt wires and the points appear to be fine. I'll check the voltage when everything is reassembled. I did however replace the points and condenser. I haven't yet been able to figure out exactly what the resistor wire is supposed to look like but from the + side of the coil there is a wire going to the R side of the solenoid (it was been replaced at some time) and a black wire headed for the bulkhead. If someone could post a picture of the resistor wire I would appreciate it. I need to figure out if it's also been replaced.
frm what I could find in a brief search is this coil will function from 9 volts to 14 volts if its a factory good coil. I have read that there are bad batches of MSD coils from their suppliers. So the voltage shouldnt be an issue of why this is getting hot. I would do the resistance ohm readings and see if its within specs...maybe its under voltage and thats why its getting hot much like a motor that is running on too little amperage and it overheats due to working to hard to get the amperage it needs
How do you know what brand coil he is using?
Typically coil manufacturers specify whether a resistor is supposed to be used to prevent burning out the coil.
From: I'd like to propose a toast... to internal combustion and wind in the face.
Originally Posted by Rescue Rogers
frm what I could find in a brief search is this coil will function from 9 volts to 14 volts if its a factory good coil. I have read that there are bad batches of MSD coils from their suppliers. So the voltage shouldnt be an issue of why this is getting hot. I would do the resistance ohm readings and see if its within specs...maybe its under voltage and thats why its getting hot much like a motor that is running on too little amperage and it overheats due to working to hard to get the amperage it needs
I did test the coil's resistance and though I can't remember the values off the top of my head it was within specs.
From: I'd like to propose a toast... to internal combustion and wind in the face.
Originally Posted by MelWff
What is the voltage reading on positive terminal with engine running?
I removed the coil before testing its resistance. My plan, after finishing the visual inspection, is to reassemble, install a battery cut-off and finally perform the diagnostic tests. I saw some smoke up around the distributor the last time the car was running so the car won't see any electricity before having a proper battery cut-off.
From: I'd like to propose a toast... to internal combustion and wind in the face.
Originally Posted by MelWff
How do you know what brand coil he is using?
Typically coil manufacturers specify whether a resistor is supposed to be used to prevent burning out the coil.
does it say anything on the coil about external resistor required?
What part number? It should start UC-12.
Need the voltage reading on positive terminal with engine running.
From: I'd like to propose a toast... to internal combustion and wind in the face.
Originally Posted by MelWff
does it say anything on the coil about external resistor required?
What part number? It should start UC-12.
Need the voltage reading on positive terminal with engine running.
From: I'd like to propose a toast... to internal combustion and wind in the face.
Originally Posted by donaldb1
If the original resistance wire has been removed, this is needed .
You're likely correct. right now I can't tell if the wire going to the coil is in fact a "resistor wire" or not. I'd appreciate it if someone could post a picture of the resistor wire.
Resistor wire is black/pink and should say in very small print "resistor" on the insulation. Note the '72 resistor wire is a different color than '71. If I recall I could not see the pink well on my '72 resistor wire. Looked mostly black in color. If its spliced, then go back before the splice to investigate. Its taped up in the harness as it goes to the bulkhead so hard to follow. Has the harness tape been disturbed? Regardless, if it has been spliced at all, you should replace with a complete new wire from the bulkhead. Soldering in a new wire, even if a portion of an old resistor wire probably not a good idea. Resistance causes heat, if not calibrated correctly, could cause wire to burn up along with potential fire. Happens and not uncommon. Still wonder what voltage you are actually getting with this current wire.
You're likely correct. right now I can't tell if the wire going to the coil is in fact a "resistor wire" or not. I'd appreciate it if someone could post a picture of the resistor wire.
Factory setup is two wires using a single horseshoe shaped connector
From: I'd like to propose a toast... to internal combustion and wind in the face.
Thanks for letting me know what to look for on the resistor wire. Though the wiring harness has been messed with at some time in the past in the area of the distributor it is for the most part undamaged or touched within inches of the coil and as the wiring harness nears the brake booster. I still have to get under the car to see what the wiring harness condition is at the bulkhead. If the resistor wire has been replaced or cut then I may be installing a ballast resistor.
I did reassemble the cap, plug wires and coils wires last night. Now to reattach the starter wiring. What a bummer.
The only Corvette manual that I have is for a 1963. It shows a ressitor similar to the photograph that I posted earlier. I disrember what year the resistance wire was born. I have two vehicles that are points distribuors and will post picts of their connections. Note that these are old and may have been adjusted to suit the owners desires. this is the wire recently removed from coil. This coil. I ran this truck for several years as a 3/4 ton dump truck so( believe this is orginal i just remberded that this gmc was a v6 and someone replaced iwth a 400SBC before I got it.. 1969 GMC
Last edited by donaldb1; Nov 1, 2022 at 04:06 PM.
Reason: told an untruth
The only Corvette manual that I have is for a 1963. It shows a ressitor similar to the photograph that I posted earlier. I disrember what year the resistance wire was born. I have two vehicles that are points distribuors and will post picts of their connections. Note that these are old and may have been adjusted to suit the owners desires. this is the wire recently removed from coil. This coil. I ran this truck for several years as a 3/4 ton dump truck so( believe this is orginal i just remberded that this gmc was a v6 and someone replaced iwth a 400SBC before I got it.. 1969 GMC
I believe starting in 68 with the new C3 they discontinued the ceramic resistor.
