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TO30 Generator/charging diagnosis

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Jim

09-11-2000 17:57:23




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The battery on my TO30 has abruptly ceased to hold a charge. I have no idea how old it is, as the tractor is a recent purchase. The battery seemed perfectly healthy when I bought it, and stood up to several sessions of frequent starts and short runs while I tweaked the tune-up settings and linkage adjustments. My question is, how do I tell if it's the battery or another component of the charging system, such as the generator or voltage regulator? I know the most likely culprit is the battery, but I don't want to just start throwing parts at it, and $500 later find out what the real solution was. I have a shop manual that details the generator output specs. I should be able to read charging voltage at the battery while the tractor's running, correct? I get about 5 volts on the freshly charged battery right after starting, but after running for a bit, it drops to 3 or 4. Should I also be able to read charging voltage at the generator, across the "A" and "Field" terminals? I get zip when I connect the voltmeter across those terminals. The ampere meter on the dash barely twitches, if it moves at all, while the engine's running. Does this sound like battery, generator, or otherwise? At the risk of sounding more stupid, if my generator has indeed bought the farm, where is the electricity coming from to power the coil and spark plugs? Sorry this is so long. Thanks to all who have the patience to read it and answer.

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D hartman

09-13-2000 04:27:53




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 Re: TO30 Generator/charging diagnosis in reply to Jim, 09-11-2000 17:57:23  
The surest way to tell If your Generator is putting out is to start the tractor and while it is running at a mid to high rpm, take off either battery lead. If the tractor still runs...your generator and cutout relay contacts are good. At this time put a voltmeter across the 2 leads that go to the battery....one that is still connected and the other one you just took off. Read the voltage...this is the nonloaded output of the generator. Hopefully it is 7-8 volts. The voltage regulator has two main functions....one is to cutout or disconnect the armature of the generator from the battery at very low rpms of the engine. At low speeds the generator puts out less volts then the battery causing an actual discharge of the battery. When the rpms of the engine come up,the voltage output of the generator ("A" lead coming into the voltage regulator)comes up also and the cutout relay picks up to tie the generator output into the battery to charge it. The second main function of the voltage relay is to Semi-regulate the output of the generator. This is a 2 step method of control based on the other relay(not the cutout relay)inside the voltage regulator. Basically this relay is either dropped out...which ties the "F" terminal (the field which is self excited of the generator) to chassis ground. This allows maximum current to flow thru the generator field which in turn tells the generator to put out full voltage. If the relay is picked up the contacts open and a resister is tied in between the "F" wire ( generator field) and chassis ground. This reduces the current flow thru the field...hence the generator puts out less voltage...kind of like a trickle charge. Make sure there is a good connection between the mounting feet of the regulator and the chassis, or the field current will be not correct...causing low generator output.

sorry this is so long...but I hope it helps with troubleshoot your problem.

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D hartman

09-13-2000 04:27:33




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 Re: TO30 Generator/charging diagnosis in reply to Jim, 09-11-2000 17:57:23  
The surest way to tell If your Generator is putting out is to start the tractor and while it is running at a mid to high rpm, take off either battery lead. If the tractor still runs...your generator and cutout relay contacts are good. At this time put a voltmeter across the 2 leads that go to the battery....one that is still connected and the other one you just took off. Read the voltage...this is the nonloaded output of the generator. Hopefully it is 7-8 volts. The voltage regulator has two main functions....one is to cutout or disconnect the armature of the generator from the battery at very low rpms of the engine. At low speeds the generator puts out less volts then the battery causing an actual discharge of the battery. When the rpms of the engine come up,the voltage output of the generator ("A" lead coming into the voltage regulator)comes up also and the cutout relay picks up to tie the generator output into the battery to charge it. The second main function of the voltage relay is to Semi-regulate the output of the generator. This is a 2 step method of control based on the other relay(not the cutout relay)inside the voltage regulator. Basically this relay is either dropped out...which ties the "F" terminal (the field which is self excited of the generator) to chassis ground. This allows maximum current to flow thru the generator field which in turn tells the generator to put out full voltage. If the relay is picked up the contacts open and a resister is tied in between the "F" wire ( generator field) and chassis ground. This reduces the current flow thru the field...hence the generator puts out less voltage...kind of like a trickle charge. Make sure there is a good connection between the mounting feet of the regulator and the chassis, or the field current will be not correct...causing low generator output.

sorry this is so long...but I hope it helps with troubleshoot your problem.

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Bill Mc

09-12-2000 16:22:52




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 Re: TO30 Generator/charging diagnosis in reply to Jim, 09-11-2000 17:57:23  
Hi Jim my TO20 did the same thing.First check the generator brushes.Make sure the brushes are touching the commutator,clean the carbon dust out with air NO CHEMICALS . Also check the brush springs.Next remove the voltage regulator(disconnect battery first)check the cut out relay contact with an ohmmeter. Ohmmeter should read 0.1 ohms. If the contact reads higher then say 1 ohm then clean and polish it with 600 grit emery cloth. recheck the resistance until you have it clean. Cleaning the cutout relay cured my charging problem.I think with a charged battery and tractor running the voltage should be 7 to 8 volts.If you have any more questions post back or email me .Good Luck

Bill Mc

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SandyB@TN

09-12-2000 14:05:18




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 Re: TO30 Generator/charging diagnosis in reply to Jim, 09-11-2000 17:57:23  
Jim,
If I remember correctly, you should be getting 7+ volts at the battery while running. Sounds like either the generator or voltage regulator is not doing it's job. Charge the battery and take it to one of the auto parts places that checks such things. That will eliminate the battery one way or the other. If the generator or voltage regulator is bad, you are running off the battery at this time...which will last pretty fast. With a good battery and plenty of charge you can run 2 or 3 hours. If the battery is on it's last legs, it'll run 10 or 15 minutes and start missing pretty badly. Sorry I can't help more. It's been a long time since I messed with generators and their attendant idiocyncracies.
HTH
Sandy

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