Positive ground on 1967 4020LP?

[2520-4010]

I recently bought my MIL a 1967 4020LP. I drove it home and started it again just a couple of days ago.

This morning, I went out and tried to start it to do some routine maintenance and was going to start plumbing in the 158 loader into the hydraulic system.

It wouldn't even turn over....no alt light, nothing. Got my charger out to charge the batteries and noticed that the negative post is hooked to the starter and the positive to ground. Is this possibly the way its supposed to be? The auctioneer stated that it had been to the JD shop to fix a few things. If they replaced the battery (it looks like it could be new) it would have only been on the tractor a couple of weeks.

So, is there any reason it would start if it has been hooked up backwards....and should I change it to neg ground and see what happens?

 

[John T]

Best I recall, NO WARRANTY. The New Generation WHILE STILL GENERATOR EQUIPPED were POS Ground, while after Alternator equipped were NEG Ground

If its NEG ground alternator and the battery was hooked up backwards (POS Ground) it may be fried !!!!!!!!!!!!!!!! and the battery got discharged.

If Generator it can work at EITHER Polarity provided its properly polarized

The starter can still work and turn the right direction AT EITHER POLARITY

Since you state "no alt light" my best guess is it should be NEG ground if it has an alternator (unless a rare POS ground alternator was used I doubt) so the battery got discharged and the alternator may be fried. Charge the battery and give it a try to see if it will charge DONT HOLD YOUR BREATH

John T

 

[Tx Jim]

'67 4020 LPG tractor will have factory installed positive ground electrical system

 

[2520-4010]

Thanks for the replies.......I did some google-fu while I was waiting and found old threads that stated the same as you. That most any tractor JD that had generators had pos ground.

Anyway, I found the problem. It wasn't a dead battery....it must have a loose wire on the ignition switch. I gave the dash a good wack with my fist and the alt light started shining bright. Pushed the starter and still nothing. Gave it another wack and the starter engaged and ...whoopee, just like new.

Later I will take the panel off and find the loose wire, hopefully.

Thanks again!!

 

[John T]

Congratulations

John T

 

[miangus]

Wow, you have a real original tractor that no one has rewired to negative ground.

 

[jsborn]

(quoted from post at 12:20:18 09/13/20)

Anyway, I found the problem. It wasn't a dead battery....it must have a loose wire on the ignition switch. I gave the dash a good [b:67143e9cd0]wack[/b:67143e9cd0] with my fist and the alt light started shining bright. Pushed the starter and still nothing. Gave it another [b:67143e9cd0]wack[/b:67143e9cd0] and the starter engaged and ...whoopee, just like new.

Later I will take the panel off and find the loose wire, hopefully.

Thanks again!!

In Proper Technical terms that was a calibration pulse not a wack.

As the repairman said I dont get paid for working I get paid for knowing where to hit it.

Glad you got it back going.