ignition resistor in our little cars?

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ignition resistor in our little cars?

Post by Esasky's62Lark on Tue May 24, 2016 8:15 am

Gents,

Are our cars equipped with the GM resistor wire going to our distributors? Reason I ask is I did the Pertronix points swap on my stock distributor and wanted to know if I am going to have to take resistor wire out and do a 12 ignition swap or not.

I know the Pertronix points eliminator kit runs off of 8-16 VDC. I didn't see anything in the directions about having to run a ballast resistor or keep the GM resistor wire in.

Thanks!

Chris
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Re: ignition resistor in our little cars?

Post by dowxxpa on Sun May 29, 2016 3:02 pm

Hi Chris.
Yes, there is a resistor wire that will have to be replaced or bypassed. FYI, I put a Pertronix in my car and it ran OK for a month or two, then quit suddenly leaving me stranded. I called Pertronix for help, they strongly suggested double checking the voltage UNDER LOAD at the distributor, and sure enough that was the problem. The resistive wire goes from under the dash, through the firewall, and is inside the wire bundle running along the top of the firewall. But the resistive wire does not go all the way, only about half way. If you unwrap the bundle you will find a cloth covered wire that mid-way is spliced to a normal wire (red I think, not sure). So the wire you see coming out of the harness to the distributor is a normal wire, not resistive. I guess the Buick engineers calculated the length of resistive wire needed to get the resistance value they wanted. Anyway, Pertronix told me they've seen their units run on low voltage for long periods, but they eventually quit. Don't risk being stranded. Replace or bypass the wire. It really wasn't that bad a job to unwrap the harness and re-wrap it, just tedious. I left the resistance wire in place in case I ever want to go back to points. I ran a new wire from the source to the splice, problem solved. I am a fan of the Pertronix system. It has been completely trouble free ever since, and no points to bother with. I've put over 3,000 miles on my car since finishing it. And I am definitely getting a better spark since getting that resistance wire out of the circuit. I'm doing a '61 Beetle now and will put Pertonix in it too.
All the best
Pete

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Re: ignition resistor in our little cars?

Post by Esasky's62Lark on Sun May 29, 2016 8:33 pm

Pete,

Thanks for the information. My plan is probably to just run a 12 VDC ignition wire to the distributor. Figured if the resistive wire was easy to get to, I may just swap it. We will see.

Looking forward to getting Pertronix system up and running.

Chris
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Re: ignition resistor in our little cars?

Post by keithg on Wed Jun 01, 2016 9:00 am

The resistor wire on a 62 is yellow (maybe with a red stripe?).

I just went through this. The wire runs from the ignition switch through the firewall, across to the passenger side to the battery and then across to the coil. I am running a 'normal' coil and ran a new pair of wires from the ignition switch to the coil (one from 'start' and one from 'run'). On my 50+ year old car, my wire was hard and cracked had high resistance. I was getting ~5v at the coil making it hard to start/run as someone had removed the 12V start wire from the ignition switch. I put a Chrysler style ballast resistor under the cross brace (next to the master cylinder) and ran the wire up the driver side fender and across to the coil (Mine is bolted to the head).

I know the Pertronix coil has an internal ballast resistor. Just make sure you are getting 12V to it when cranking and also when running. With the MSD Blaster 2 coil (and external ballast resistor) I am running, the low end pull is so much smoother than the 50+ year old stock coil with only 5V at the coil when running! (never before, but now, I can release the clutch then roll on throttle and it easily just pulls). Pertronix suggests a 12ga wire from the ign switch. I did not have this gage on hand in nicely flexible wire and am running 14Ga which is bigger than what GM used as stock. Keep in mind that the coil will draw about 8A when running.


Last edited by keithg on Mon Dec 12, 2016 8:56 am; edited 1 time in total

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Re: ignition resistor in our little cars?

Post by Esasky's62Lark on Wed Jun 01, 2016 10:56 am

keithg wrote:The resistor wire on a 62 is yellow (maybe with a red stripe?).

I just went through this. The wire runs from the ignition switch through the firewall, across to the passenger side to the battery and then across to the coil. I am running a 'normal' coil and ran a new pair of wires from the ignition switch to the coil (one from 'start' and one from 'run'). On my 50+ year old car, my wire was hard and cracked had high resistance. I was getting ~5v at the coil making it hard to start/run as someone had removed the 12V start wire from the ignition switch. I put a Chrysler style ballast resistor under the cross brace (next to the master cylinder) and ran the wire up the driver side fender and across to the coil (Mine is molted to the head).

I know the Pertronix coil has an internal ballast resistor. Just make sure you are getting 12V to it when cranking and also when running. With the MSD Blaster 2 coil (and external ballast resistor) I am running, the low end pull is so much smoother than the 50+ year old stock coil with only 5V at the coil when running! (never before, but now, I can release the clutch then roll on throttle and it easily just pulls). Pertronix suggests a 12ga wire from the ign switch. I did not have this gage on hand in nicely flexible wire and am running 14Ga which is bigger than what GM used as stock. Keep in mind that the coil will draw about 8A when running.

I plan on running the stock can coil on mine. Just running the Pertronix points conversion in the distributor.

I know that that needs 12 VDC in the crank and run position. Question is now, can the stock coil (one with resistor wire usually attached) handle the full 12 VDC ignition signal now or should I just change the coil to an aftermarket too?

Chris

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Re: ignition resistor in our little cars?

Post by keithg on Wed Jun 01, 2016 1:45 pm

Chris,

I'm running the pertronix points eliminator and a Blaster 2 coil. The coil needs 12V at crank and ~8V at run. OEM and most aftermarket coils (MSD, Accel, etc.) will require a ballast resistor or resistor wire to drop the voltage to the coil when running. The exception is the Pertronix coil which is designed to be run at 12V for both start and run. This is why they ask you to bypass the 'resistor wire' or short the ballast resistor.

The original design on the Buick is such that you get full battery voltage during cranking then it drops back to ~8V when running. There are 2 poles on the ignition switch one for RUN and one for START. The START has a regular copper wire which runs to the coil and gives it 12V. The RUN has a 'resistor wire' on GM cars and a 'Ballast resistor' on Chryslers and maybe Fords (I do not know for sure what Ford does) to drop the voltage to ~8V when running. To achieve the same effect as the 'resistor wire' GM used, you will have to use regular copper wire and a ballast resistor to replace the old 'resistor wire'. This is what I did on mine and the drive-ability and starting performance improved dramatically, especially when hot.

GM has designed the 'resistor wire' so it can 1) pass ~8A while running without getting too hot and burn up the harness and 2) drop the voltage to ~8V at the coil. There is a bypass wire which gives the coil full battery voltage when cranking (Black Wire on the wiring diagram - I linked to the diagram in my other thread on this Topic on ignition ).

My guess is that your 'run' wire probably drops the voltage below the ~8V when running being it is 50+ years old and may even have been spliced at some time (Mine was). The ballast resistor was about 5.00 at AutoZone. The spool of wire was more... Best to start the car and then measure the voltage at the coil + terminal when idling. It should be about 8V. You really should not give a coil 12V when running as you will overheat it eventually and weird things will start to happen (Stalling, sputtering, etc).

Keith (in Chicago)

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Re: ignition resistor in our little cars?

Post by Esasky's62Lark on Wed Jun 01, 2016 2:01 pm

keithg wrote:Chris,

I'm running the pertronix points eliminator and a Blaster 2 coil. The coil needs 12V at crank and ~8V at run. OEM and most aftermarket coils (MSD, Accel, etc.) will require a ballast resistor or resistor wire to drop the voltage to the coil when running. The exception is the Pertronix coil which is designed to be run at 12V for both start and run. This is why they ask you to bypass the 'resistor wire' or short the ballast resistor.

The original design on the Buick is such that you get full battery voltage during cranking then it drops back to ~8V when running. There are 2 poles on the ignition switch one for RUN and one for START. The START has a regular copper wire which runs to the coil and gives it 12V. The RUN has a 'resistor wire' on GM cars and a 'Ballast resistor' on Chryslers and maybe Fords (I do not know for sure what Ford does) to drop the voltage to ~8V when running. To achieve the same effect as the 'resistor wire' GM used, you will have to use regular copper wire and a ballast resistor to replace the old 'resistor wire'. This is what I did on mine and the drive-ability and starting performance improved dramatically, especially when hot.

GM has designed the 'resistor wire' so it can 1) pass ~8A while running without getting too hot and burn up the harness and 2) drop the voltage to ~8V at the coil. There is a bypass wire which gives the coil full battery voltage when cranking (Black Wire on the wiring diagram - I linked to the diagram in my other thread on this Topic on ignition ).

My guess is that your 'run' wire probably drops the voltage below the ~8V when running being it is 50+ years old and may even have been spliced at some time (Mine was). The ballast resistor was about 5.00 at AutoZone. The spool of wire was more... Best to start the car and then measure the voltage at the coil + terminal when idling. It should be about 8V. You really should not give a coil 12V when running as you will overheat it eventually and weird things will start to happen (Stalling, sputtering, etc).

Keith (in Chicago)

Keith,

If that's the case, I may just get the Petronix coil and run a 12V start and run wire and call it a day. If I decide to go with a tube style coil other than Pertronix, I will wire in the ballast resistor in-line for the run wire.

I wouldn't be the least bit surprised if my resistance of my run wire hasn't increased causing lower voltage input at coil. I will have to dig into it when I am at that point. Nice thing is... the OEM coil was only like $12.00. :-)

I appreciate your help and explanation on this Keith. Figured I was on the right track; but its nice to have someone chime in that has done the conversion already. :-)

Chris
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