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JD A Charging Circuit

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Dale Drevdahl

11-20-2000 10:12:20




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Does anyone have a Wiring Diagram for a Late Model
JD Model A with a points type ignition system (non-magneto). I am specifically interested in the charging circuit for a Negitive Ground system.
The tractor has, I beleive a generator, not an alternator. which i would understand a little better. Im not getting 14 volts out of the thing
rather 12.4.
Any help would be appreciated.


Dale
Yamhill, Oregon

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ToddT

11-21-2000 03:34:43




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 Re: JD A Charging Circuit in reply to Dale Drevdahl, 11-20-2000 10:12:20  
Dale,

Here is a link to a late A wiring diagram.



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clooney

11-20-2000 11:50:20




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 Re: JD A Charging Circuit in reply to Dale Drevdahl, 11-20-2000 10:12:20  
Dale, the 2 cylinder J.D.s all had positive ground,are you sure yours has a negitive ground? If it has been converted to negitive ground has the generator been polorized to charge that direction? If not, with the regulator still hooked up momentairly hook a jumper wire from the BAT terminal to the GEN (or arm) terminal on the regulator (it should spark a little)...CAUTION: don't touch a hot wire to the F or FLD terminal of the regulator or generator at any time. See the link below for a positive ground J.D. A system, everything will be hooked up the same, just the + & - will be reversed at the battery on your tractor (the diagram will be correct for either polarity as it is not marked).

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John T

11-20-2000 11:15:39




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 Re: JD A Charging Circuit in reply to Dale Drevdahl, 11-20-2000 10:12:20  
Dale, the fully charged voltage of whats called a 12 volt battery is around 12.6, so if its not raising above that with the tractor at a high rpm, its probably not genning. Things to check are first belt tightness and belt condition, then I can guide you through troubleshootung to see if its the Voltage Regulator (VR) or the Generator itself. First, insure wiring continuity out of the VR to and through the series ammeter (if you have one) then it has to get to the battery to charge it, usually by a wire from ammeter - to the starter post big lead. You can first troubleshoot the VR by running a jumper out of the generators field terminal to case ground and see if that makes it gen. Then, you can test the VR cutout relay by changing the wire from the VR Bat terminal over to the Arm or Gen VR terminal (with other wire still left on the VR's Arm or Gen terminal) with the tractor running to see if she charges then. If thats done when tractor is shut off, it can reverse discharge the battery, so unhook it. Dont touch any hot wires to the Fld terminal or wires. If a bad generator, its often stuck corroded generator brush hold down springs thats all the trouble. Do some troubleshooting and tighten the belt and wire brush and air clean and spray the brush hold down springs and post back. Ol John T Engineer in Indiana

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Tom

11-21-2000 16:03:12




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 Re: Re: JD A Charging Circuit in reply to John T, 11-20-2000 11:15:39  
You people all sound so smart. Does this information apply to a John Deere model 70 gas? I had the starter and generator rebuilt a couple of years ago and havent been able to get it to charge since. For some reason, there are two (2) wires running from my voltage regulator instead of the single wire shown in the diagram.

Thanks



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John T

11-22-2000 06:19:29




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 Re: Re: Re: JD A Charging Circuit in reply to Tom, 11-21-2000 16:03:12  
Tom, Yes, all I said above about the A and how to troubleshoot it applies to your 70. Just re read it and do the same. That Bat terminal on the VR has to have battery voltage on it (a wire to and through any series ammeter then to the battery), otherwise, even if the gen is working, it isnt getting to the battery to charge it. Then, if the VR cutout relay is working properly, that isnt internally conected over to the Gen/Arm terminal until the generator voltage rises to charge the battery. Take a jumper, and with the tractor running, ground the Field terminal and see if she charges then. If so, its a faulty VR. Then with the tractor running, if the wire going to the VR Bat terminal is hooked over to the Arm or Gen terminal and she charges, again, its a faulty VR (cutout relay not closing). If neither of those makes her gen and the wiring is all intact, its likely a bad generator usually a brush or brush hold down spring problem. Also, you can remove the generator belt and with the field grounded and voltage appled to the Arm terminal on the generator, if working she will motor (run) if its good. Let me know what your troubleshooting tells you and you can worry about where to hook your light circuit (L) later. Ol John T Engineer in Indiana

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clooney

11-21-2000 16:53:35




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 Re: Re: Re: JD A Charging Circuit in reply to Tom, 11-21-2000 16:03:12  
Tom, I don't know how smart we are but we try,, You have posted a real good question. There are 2 different voltage regulators listed for a 70 + a couple of replacments offered. Sooo, all I can tell you is that some 70s used an L terminal and some didn't. The "L"terminal would have a black wire on it & run from the voltage regulator to the light S/W. The other wire running to the rear would be white & run from the BAT terminal on the regulator to the ammeter. First thing you should check is that you have battery voltage (12V) at the BAT terminal on the regulator. Then make sure there is a wire running from the GEN terminal of the reg. to the ARM terminal of the generator (bigger of the two), & a wire running from the FLD terminal of the reg. to the F terminal of the generator. If all OK there then with the tractor running run a ground wire from the F post (smaller of the 2 posts) on the generator to the a bare spot on the frame or generator body (if it charges now you have a bad reg or bad reg ground), if still no charge then with the tractor not running momentairly touch a wire from the BAT terminal of the regulator to the GEN terminal of the regulator (CAUTION: do not touch a hot wire to the FLD or F on either the reg. or gen.) you should see a small spark, then run & see if it charges, if still no charge post back for further details. For now don't worry about the "L" terminal until after you get it charging, in fact remove the wire from the regulator until you get it charging.

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Tom

11-27-2000 14:30:24




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 Re: Re: Re: Re: JD A Charging Circuit in reply to clooney, 11-21-2000 16:53:35  
Thanks for your advice on my model 70 charging problem. I had intended to work on it this weekend and return to you today with a favorable report. My wife had another idea.

Anyway, I'll try your suggestions as soon possible and let you know how it works out. Thank you both for your help.



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