I think it’s the Ballast resistor?

HWYCRZR

Old Man with a Hat
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‘68 Polara 383 2bbl. I started down the road to a car show about 60 miles away. I got about 10 miles away from home and I felt a little stumbling. I Stopped to check it out. It was idling smoothly, rev it up, still smooth. It seemed one of the wires on the ballast resistor was loose so I pushed it on further and got a quick stumble while I was pushing. Then ran smooth again.
I really wanted to continue on, knowing I should turn back while it was running. So I continued. At about 30 miles in, it started stumbling again. A little bit surging and sputtering. I slowed to 60 and it was still kind of hit and miss. This wen on for about 2 miles and then started running smoothly again. At about 40 miles in it did it again. This time a little backfire. I pulled into a small town and it was running fine again. I opened the hood and got it to stumble again. I was 43 miles from home I decided I should probably head home to get closer instead of further away. On the way home it happened 2 or 3 more times but made it. Now to try and diagnose an issue that is not consistent.
 
When I got home I took my multimeter to measure the voltage going through the ballast resistor. It was at 9.7 volts. Then it started missing and would drop to 9.3 on the miss. I didn’t think that was enough of a drop to cause the coil to miss fire. I decided to grab the FSM to look at the ballast resistor specs. No voltage specs, but current draw and ohms resistance. Resistance was supposed to be .5 -.6 ohms at 70–80 degrees. I was at 1.2 ohms resistance, more than double. I took it off the fender and this is what I found when I looked at my 1985 vintage ballast resistor.
Time for a new ballast resistor.
C710B6D5-8090-450E-B31A-B7325A7237CB.jpeg
 
I had the same issue with the 300 a while back. I had it running at an idle and was checking wires etc. I got to the ballast resistor connections and it did as you described. Pulled out the spare resistor and problem solved.
 
As I was reading through the FSM it had a couple of specs to measure coil current draw. The spec was to measure including the ballast resistor. One with ignition on and one running. I need to run it in series. Am I right in thinking I would unhook the positive wire from the coil, and hook my multi- meter in between the positive feed wire and coil. Or do need to between the ignition wire and ballast resistor to get the full circuit. I am thinking the latter.

The FSM said follow the instructions from the coil manufacturer.:mob:

Am I on track
 
I don't recall the specs for voltage at the resistor and am in the house comfortable now. :) I did check it according to the service manual and it was as stated in the FSM. I found that the problem was on the resistor end from the space to the resistor winding. Go from the ignition wire to the resistor IIRC.
 
I don't recall the specs for voltage at the resistor and am in the house comfortable now. :) I did check it according to the service manual and it was as stated in the FSM. I found that the problem was on the resistor end from the space to the resistor winding. Go from the ignition wire to the resistor IIRC.
Thanks. Thinking through it I kind of came to the same conclusion. The current spec for my coil and resistor is 3 ampers with engine stopped ( my measurement was 4 amp)
Running spec at idle is 1.9 amp ( measured 2.5). It would drop to 1.9 amps @1000 rpm. The coil is still pretty warm from my trip so I will wait until tomorrow to measure again.
The new ballast resistor is measuring at .7 ohms, a touch higher than spec (.5-.6 ohms)
Will have to try another road trip in a day or two.
 
I know I should have a spare. But I don’t.
 
When I got home I took my multimeter to measure the voltage going through the ballast resistor. It was at 9.7 volts. Then it started missing and would drop to 9.3 on the miss. I didn’t think that was enough of a drop to cause the coil to miss fire. I decided to grab the FSM to look at the ballast resistor specs. No voltage specs, but current draw and ohms resistance. Resistance was supposed to be .5 -.6 ohms at 70–80 degrees. I was at 1.2 ohms resistance, more than double. I took it off the fender and this is what I found when I looked at my 1985 vintage ballast resistor.
Time for a new ballast resistor.
View attachment 397895
LoL!!!! That’s how I blew the mufflers off my `68. KaBOOM !!!!!

You lucky.
 
If I would have had a spare I would have continued on. I have about 50 lbs of tools in the trunk, an extra points set, condenser, rotor and cap. But no ballast resistor. And guess who didn’t buy an extra ballast resistor for $5.00 when I picked up my other one tonight.
 
Carry an extra coil. That’s probably the next thing to swap on your car to see if the intermittent problem goes away.
 
I carry a bag of BR's in the glove box.

Lately the new ones haven't been lasting very long. 2 in the matter of five thousand miles approximately.
 
LoL!!!! That’s how I blew the mufflers off my `68. KaBOOM !!!!!

You lucky.


I had a similar instance when the car shut down I coasted into a Walgreens parking lot. After a couple minutes of sitting I tried to start it and bang with a flash. The car started up but the bang set of the alarm system and all the lights in the store came on . ( this was around midnight)
 
I had a similar instance when the car shut down I coasted into a Walgreens parking lot. After a couple minutes of sitting I tried to start it and bang with a flash. The car started up but the bang set of the alarm system and all the lights in the store came on . ( this was around midnight)
That’s hilarious!
 
If I would have had a spare I would have continued on. I have about 50 lbs of tools in the trunk, an extra points set, condenser, rotor and cap. But no ballast resistor. And guess who didn’t buy an extra ballast resistor for $5.00 when I picked up my other one tonight.

I usually carrey an extra voltage regulator,too.
Cheap spare part in case of a loading problem
 
I had a similar instance when the car shut down I coasted into a Walgreens parking lot. After a couple minutes of sitting I tried to start it and bang with a flash. The car started up but the bang set of the alarm system and all the lights in the store came on . ( this was around midnight)
Mine was a WTH? moment after filling up. I almost blew the windows out of that gas station. The lady came out and told me to GET the F$&@ OUT of her parking lot!!!!

We pushed it out into the dirt for a little checking and sure enough found a broke in half caterpillar...

Good times.
 
I do admire you guys with the great diagnostic abilities but with ballast resistors I just always carry a spare and swap it out at the first sign of trouble. If it fixes it great if not then it's crying time.
 
I do admire you guys with the great diagnostic abilities but with ballast resistors I just always carry a spare and swap it out at the first sign of trouble. If it fixes it great if not then it's crying time.
Mine gave no warning & my spare was about a thirty minute walk away. No cell phones no goober rides just feet & pay phones.
 
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