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Allis Chalmers Discussion Forum
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12-volt conversion followup ?

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RobJJ

04-04-2007 13:48:33




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Hmm,
Prior posts were awesome. So here is what I took from all that. The battery was hooked up with a negative ground rather than pos. ground - that was wrong! Is there any conceivable reason why this might have been done deliberately? Is there a way to determine if it SHOULD be negatively grounded?

If not, what could have been damaged in the process? The auto parts store says the battery appears shot...might that be due to having been hooked up wrong?

What about the generator? Is it likely junk having tried to charge an incorrectly hooked up battery?

I see a couple of approaches. I can buy a new 6 volt, hook it up pos. ground and see what happens. Not sure at this point if the ammeter works as I have seen no needle movement (perhaps due to the battery being hooked up wrong?). Assuming the ammeter is broke, is there a way to tell if the generator is functioning? (I have a voltmeter if that helps).

Or, I can say screw it, junk the 6-volt system and make the conversion to 12 volt, rewire using the diagrams I've found on the site, and call it good. [I'd prefer to keep it 6-volt just for originality, but not at the expense of major additional costs, or headaches.]

Or I can drop in the 12 volt battery temporarily, and see if the starter works. If I do that, should I first disconnect the generator? Would I disconnect all wires from it, or would I need to leave some connected? Also, if I do that, do I hook the battery up pos. or neg. ground?

Anyway, mostly I'm wondering what affect the battery, having been hooked up wrong, might have had on the overall electrical system.

Thanks VERY much to all who have replied.

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Kent of SWMO

04-05-2007 15:46:57




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 Re: 12-volt conversion followup ? in reply to RobJJ, 04-04-2007 13:48:33  
Allis-Chalmers equpment used positive ground until they started equipping their products with alternators. When They went to alternators the grounding changed to negative. I have a 66 Gleaner that was 12 volt positive grd. Dad has two that were positive grd. Uncle has one that was positive grd. They have all been changed to Alternators and electronic ignition. My bother-in-law's Gleaner is stil positive grd. His still has the generator. All of these Gleaners are C-II with the G-262 power units

Kent

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Steve in NJ

04-05-2007 04:16:58




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 Re: 12-volt conversion followup ? in reply to RobJJ, 04-04-2007 13:48:33  
I would also like to add to Steve's post, that if you decide to make the transition over to 12V down the road, when using a 12V coil, make sure that your ignition circuit has 2.7-3.3 ohms of resistance in it in order for the 4 cylinder engine to run correctly and you won't have any Ignition issues. Pick yourself up a 3.0 ohm internal resistor coil at the local Auto Parts store, or we have em' in stock and can help you out. With everything in place and setup correctly, the 6V system should work fine for another 60 years. The 6V system needs a little more attention once in a while to keep it sound and things working correctly. The grounds are super important for the 6V system for smooth charging and operation. Steve@B&B

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BCnT

04-04-2007 15:29:54




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 Re: 12-volt conversion followup ? in reply to RobJJ, 04-04-2007 13:48:33  
6 volt battery being shot is no surprise...thats one reason so many are converted...best i ever got out of a 6 or 8 volt battery was about 18 months...averaging 5 years with 12 volt



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paul sebek

04-04-2007 15:22:26




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 Re: 12-volt conversion followup ? in reply to RobJJ, 04-04-2007 13:48:33  
You said it ran fine when pull started. With the battery that weak the only way it would"ve run is with the generator running the ignition system. So it"s best to say the generator is running fine. The starters are as tough as nails, it"s most likely its fine as well. I"ll bet the battery was put in backwards by accident as there is no labeling anywhere as to which way it goes. Being backwards would explain the low battery voltage though. If you put the battery in backwards the starter will turn but won"t engage. (earlier analysis is worst case senario) If its quick the rest of the system will be unaffected. Starting will tell you immediately which way the battery goes. With the battery connected properly a quick pull from the start ring should be enough to start it. I you want to check put your voltmeter across the battery terminals when the engine is running. It should read at least 7 volts or more. The electrical system is wires, spark gaps, switches, coils, and resistors. It has no electronics so it actually is quite tough. The only polarized(magnetic) issues are the generator and starter. You could try to charge the battery and reverse it on the tractor so its the proper polarity and give it a start. Even use the start crank if you feel ambitious, just be really careful. Your ammeter should read anywhere between 2-8 amps (4 average) positive (needle left of center) when above idle and centered or lightly jumping left when idle. When you just turn on the key it should be 1 amp negative (right of center). It"s already proven it can handle a reverse connection.

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RobJJ

04-04-2007 17:37:12




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 Re: 12-volt conversion followup ? in reply to paul sebek, 04-04-2007 15:22:26  
Ok, I bought a new 6 volt battery, hooked it up, pos. ground, and the tractor started right up...the ammeter doesn't seem to move, however, so perhaps it is not functioning. I will try the tests for the generator Steve suggested, and your test across the battery terminals. While it was running, I did pull the pos. cable off the battery just to see what would happen...the tractor kept running, but I did note the rpms dropped. What might that have indicated if anything?

So, now that I know the starter is ok, my next step will be to start the tractor, and then while it is running, ground the F terminal and then put the pos. lead from the voltmeter on the A term. and neg. lead from the voltmeter on the F terminal using the voltmeter... and then I'll check the voltage of the battery across the terminals. I assume that if the voltage is greater than it was before starting the tractor, that that can only be because the generator is working. Does all this sound correct?

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paul sebek

04-04-2007 20:36:19




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 Re: 12-volt conversion followup ? in reply to RobJJ, 04-04-2007 17:37:12  
Also, after you ground the "F" terminal check the voltage at the cutoff relay on top of the generator. Both terminals should also read above 6 volts. You might want to disconnect the ground and pull up the dash assembly and check for crap inside. Mine looked like a web hotel.



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paul sebek

04-04-2007 20:06:07




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 Re: 12-volt conversion followup ? in reply to RobJJ, 04-04-2007 17:37:12  
The drop in rpm when you removed the battery cable just reflects that the generator is providing power itself without the help of the battery. The battery is a much bigger reservoir of energy than the generator. Yes, the voltage check on the battery after grounding the "F" terminal on the generator should be alot higher than 6 volts.
also the rpm has to be higher than idle for the ammeter to register anything with the engine running. When you turn the key before the engine starts you should see the ammeter move an amp or so to the left. If not the ammeter is bad or bypassed.

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steve(ill)

04-04-2007 15:16:24




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 Re: 12-volt conversion followup ? in reply to RobJJ, 04-04-2007 13:48:33  
i just read your other post. put the 12 volt battery in as i said and start it up. coilwil bo o.k. for a while, but if it is a 6 volt it will eventually crap out.---- once you are running, ground the F terminal on the generator. use a hand held volt meter and go from the "A" to the "F" terminal on the generator and see if it has any output. a 6 volt system will put out 15 volts without a voltage regulator or battery connected to it. if you have 25+ volts, you have a 12 volt generator. if you have 2-3 volts or less, your generator is in need of help. Make sure F is grounded to the case when you test this.

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steve(ill)

04-04-2007 15:09:40




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 Re: 12-volt conversion followup ? in reply to RobJJ, 04-04-2007 13:48:33  
6 volt systems were always positive ground. when they changed to 12 volt systems, they retained that ground for a few years. shortly after 1960 everything was changed to negative ground. most say this was related to the new ALTERNATORS instead of generators. You can use either 6 or 12 volts, and either + or - ground your choice. the starter does not care and the magnito dont care. if you have a distributor, you change the coil to 12 volts. the generator, if it is 6 volts, has a cutout relay not a regulator. if you go to 12 volts you normally upgrade to a 12 volt regulator and generator. or you can install a new alternator off a 1975-2000 automobile. if you put in a 12 volt battery, keep the lights off, pull the wire off the "A" terminal of the generator that goes to the cutout box, and make sure your coil is 12 volts if you have a distributor. go ahead and start it up.

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