3020 gas coil input volts

My 1967 JD 3020 gas runs strange even after I put a cast iron carburetor on it. I checked the voltage going to distributor from coil was just over 12 volts but the voltage coming from dash to coil varies from 15 down to 6 and never holds steady . I'm thinking that possibly the ignition switch needs changed unless the brain trust has other thoughts. Still has oem points and condenser but thinking on swapping it out to Pertronix.

"the voltage coming from dash to coil varies from 15 down to 6 and never holds steady"

If you are using a digital meter, the meter is simply being confused by the electrical "noise" from the ignition and charging systems and freaking out.



WHATEVER you've got going on, a (fragile) pertronix unit won't make it run and better than a fresh set of quality breaker points.

Just as a trial if you suspect a faulty resistive ignition switch is to use a jumper wire direct from battery down to coil and see how she runs and the voltage then??? (if it had an external ballast resistor you would have to account for that) If you use an old fashion analog volt meter (NOT a fancy digital read out) you may get a more true indication of the actual steady voltage to the coil. A fresh tune up of points condenser cap n rotor n plugs may be in order provided its NOT a fuel or fuel delivery problem.

John T

Wire from distributor to coil should have battery voltage with points open, near zero volts with points closed. Input to coil should read battery voltage with points open. If you have direct 12 volt coil (no resistor) it should read near battery voltage with points closed. If you have resistor or resistive wire from switch to input of coil it should read about 6 volts with points closed.

I wish I could remember if those have a resistance wire running to the coil or not ? Been a long time since I worked on our 4020 gas. For some reason I think they might because the distributer was very similar to one from a Chevy pickup engine I had laying around I robbed some items from to fix ours.
I'd get my hands on a wiring diagram for it to check for sure. Also I'd clean and inspect EVERY wiring connection one at a time from the battery all the way up to the gas tank sender ! If you can't get it working on the points and cond. I do not think a pertronics will work miracles on bad wiring.

If they exist anymore........

SWAP IT OUT ! It will make a tractor out of it .Better starting and much better warm up . You can test this by running a jumper wire to the coil input from the battery .

Make sure the points are closed and with the distributor cap off but the ignition switch in the run position you should see essentially NO volts at the coil's post on the DISTRIBUTOR side of the coil. Disconnect the meter.

Open the points by hand and again read from the distributor post of the coil to the frame. You should see battery voltage! Disconnect the meter.

If you let the points close again the distributor post voltage should again go to zero. If you read the voltage from the post on the BATTERY side of the coil you should see roughly half the battery voltage.

If you see voltages as I list here, your system is working perfectly. It is as others said, just like Chevy did in the past & used resistance wire between the switch & the coil so the coil should be receiving half the battery voltage when the points are closed. You need to take the readings with it NOT running. You need a coil that is intended for use with an external ballast resistor. Deere did as Chevrolet and used a special wire instead of a lumped porcelain resistor!

If you're trying to take these readings with the engine running it is as others have said a totally confusing situation for a digital volt meter & you'll receive readings that do not make sense!

Hope that helps.