Maybe dumb question

grandpa Love

Well-known Member
Oliver 77. Should be 6 volt but has a brand new 12 volt battery. I want to get it running. If I hook the 12 volt up positive ground all should be fine? If I were to hook it up neg ground would the starter spin the same way? No way for it to turn backwards? Or the motor to spin backwards? Be nice! Lol. Thanks!
 
As I recall, it was addressed some time ago. The starter does not care about the polarity, but the coil and amp gage do. By checking the coil, you can determine which polarity you need to hook up.
 
When we use to run natural gas pump engines for irrigation they would be hard to start if you shut them off I can remember our mechanic hooking the welder to the battery set on dc and believe me that?ll bring a dead engine to life in a big hurry . I don?t think you?d want to run it that way though
 
Just make sure your tractor has a generator and not a retrofit with an altinator. Altinator will be almost instant fry job if hooked up backwards.
 
Your coil is six volt. Easiest way to change it is to put a 12 volt coil on it. Did that with my 88 when I changed it to 12V using a 12 volt generator. I left it positive ground. I started out by leaving the 6 volt coil on it and putting a ceramic resistor in the coil primary wire with a bypass wire for starting. Must have used the wrong resistor because it was burning points even though I had 6 volts at the coil. I replaced the 6 volt with a 12 volt coil and haven’t touched the points since then.
 
If this is the tractor you just bought, and have no history on it, best to assume nothing.

Do some investigating first.

Look at the electrical system as a whole.

Is there a generator or alternator? If alternator, almost certainly it has been converted to 12v negative ground. Very important to only connect the battery negative ground!

If a generator, look it over carefully. Try to find some numbers, a brand, a voltage, some clue to what the voltage is. Same with the regulator, try to find some information on it. Most part numbers can be searched online to determine the voltage. The generator will need to be polarized to match the battery polarity, but we'll need to know what generator it has to get the proper procedure.

Look at the coil, if it is a 6 volt, and there is no resistor ahead of it, it is still set up for 6v. Look at the primary wiring to the coil. If the - terminal is connected to the distributor, it is wired for negative ground. This is not critical, it will run wired either way without damage. Just be sure when the final decision is made, positive ground system, the + terminal goes to the distributor, negative ground, the - terminal to the distributor.

If there is a ceramic resistor ahead of the coil, it has been converted to 12v. If the coil has a part number, look it up, see if it is a 6v, a 12v that needs a resistor, or a 12v that does not need a resistor. If no part number, check the resistance across the + and - terminals out of circuit. If it is around 1.5 ohms, it needs a resistor to operate on 12v. If 3 ohms, it is a 12v that does not need a resistor.

As for the starter, it will run the right direction regardless of the polarity. If it is a 6 volt starter (it probably is), it will work on 12 volts. Just be aware it is 6 volt and don't crank for extended periods of time. Most 6v starters work well on 12v, but be aware it will be slamming the drive into the flywheel gear much harder than if on 6v. Some handle it well, others don't, depends on the design of the starter.

This may sound like information overload, but just take it one step at a time. Check what you can, write down the results, post back what you find. We'll get this sorted out.
 
You can switch to negative ground if you disconnect generator, but DO NOT turn the lights on or it will suck all the light out of your shop and you will be stranded in total darkness. :) Ya I will shut up and go to bed now.
 
On 99% of generator systems the ground does not matter and being it Is a 6 volt system a 12 volt battery the VR will see and over charged battery and not even kick in. As for the coil as long as you do not run it long or leave the ignition on long the points and coil will be just fine. Yes if you run it say and hour the points will burn and you could burn out the coil. If it was say 8PM and I saw this I would have called you
 
Get a 1 wire alternator and redo the necessary parts,you will be way ahead in the long run.I wasted a lot of money over the years with generators on tractors and machinery think my
AC D19 is the only tractor here now with a generator.
 

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