JD 820 - 6 volt alternator on a 12 volt tractor?

[tommu56]

Can you put the belt on the blades and turn the engine over by hand to work it in?

I've done it on lots of engines with tight clearances, just look at it close and see if you can do it that way.

tom

 

[glenhenshaw]

I can turn the fan when it isn't connected to the belt, but I can't turn the engine over by hand to save my life. Of course, that's probably because the transmission is in park, but I can't figure out how to get it out of park without starting it. Which I can't do with the belt disconnected.

Also, even if I could turn it over by hand, there's a shaft that runs through the engine pulley, under the radiator, and into the compartment with the gas tank. It appears to be turning some kind of pump; maybe the water pump? I have to disconnect that shaft to get the belt on the engine pulley, and I can't see how to do that without taking out the radiator. So it's not just the fan that's holding me up.

 

[jenkinsph]

I can look at my 820 Sunday morning and get back with you.

The pump you are referencing on the front of the cranshaft is the hydraulic pump. It should have a coupling on it to get the belt on.

Having the transmission in park does not affect the engine, if you consider the engine runs in park position.

 

[glenhenshaw]

Hey guys,

I think I got this thing working! I finished fitting the new belt yesterday and wired the alternator into the system. The tractor started right up (although it would, given the new battery I had to buy), and there were no sparks, explosions, or shrapnel. Furthermore, there was a steady 15 volts across the battery terminals (most of the time - see below).

A few final questions:

- The pulley that came with the alternator was for a belt that was too narrow. So I pulled the pulley off the generator that was being replaced and adapted it to fit the alternator. However, that pulley was quite a bit larger in diameter than the pulley that was originally on the alternator, which means the alternator spins a bit more slowly than it would otherwise. And when the tractor is at a dead idle, there's only 12.5 volts across the battery leads. When I give it a bit of gas the voltage jumps to 15 and stays there. Does anybody think that's going to be a long-term problem?

- I'm not 100% convinced I got the wiring exactly right. The alternator "BAT" terminal goes directly to the positive battery terminal. According to the wiring diagram that came with the alternator, terminal "2" is also supposed to go directly to the positive battery terminal, so I wired "2" and "BAT" together. Terminal "1" is supposed to go to the output of the indicator lamp, which it does (although the indicator lamp itself is clearly busted - ordered a new one but it won't come in until later this week). There is no ground wire; I assume the alternator is grounded through its housing. Does the wiring sound right?

Thanks for all the help!

 

[kuboman]

Hey guys,

I think I got this thing working! I finished fitting the new belt yesterday and wired the alternator into the system. The tractor started right up (although it would, given the new battery I had to buy), and there were no sparks, explosions, or shrapnel. Furthermore, there was a steady 15 volts across the battery terminals (most of the time - see below).

A few final questions:

- The pulley that came with the alternator was for a belt that was too narrow. So I pulled the pulley off the generator that was being replaced and adapted it to fit the alternator. However, that pulley was quite a bit larger in diameter than the pulley that was originally on the alternator, which means the alternator spins a bit more slowly than it would otherwise. And when the tractor is at a dead idle, there's only 12.5 volts across the battery leads. When I give it a bit of gas the voltage jumps to 15 and stays there. Does anybody think that's going to be a long-term problem?

- I'm not 100% convinced I got the wiring exactly right. The alternator "BAT" terminal goes directly to the positive battery terminal. According to the wiring diagram that came with the alternator, terminal "2" is also supposed to go directly to the positive battery terminal, so I wired "2" and "BAT" together. Terminal "1" is supposed to go to the output of the indicator lamp, which it does (although the indicator lamp itself is clearly busted - ordered a new one but it won't come in until later this week). There is no ground wire; I assume the alternator is grounded through its housing. Does the wiring sound right?

Thanks for all the help!

I would have thought that #2 would go to a switched connection such as the ignition or something that will not be energized when the tractor is off. Otherwise won't the alternator cause a drain with the engine off? Just my thoughts. I am no expert by any means.

 

[glenhenshaw]

The indicator light is in series with the ignition switch... but to be honest I don't know what it is for. Does it light when you are getting a charge, or when you aren't?

 

[kuboman]

The indicator light is in series with the ignition switch... but to be honest I don't know what it is for. Does it light when you are getting a charge, or when you aren't?

Usually the light is to indicate a no charge situation.

 

[jenkinsph]

I would have thought that #2 would go to a switched connection such as the ignition or something that will not be energized when the tractor is off. Otherwise won't the alternator cause a drain with the engine off? Just my thoughts. I am no expert by any means.

That is what I am thinking, #2 goes to the ignition circuit the third wire to the altermator light. When the ignition is turned on the alt light should light up and when the engine is running with alternator charging the battery the light should go off. I am no expert either.

 

[bbrown4804]

Your #2 wire just goes to the BAT post on the back of the alternator. This is what's called your "sense" wire. It tells your alternator what the battery's voltage is and when to charge. The #1 wire is connected to your switched ignition circuit, warning light or diode in line. This wire should only be hot when the key or switch is in the on or run position. I'll attach a basic 10si alternator diagram, just don't pay attention to that it says its for a Super M. haha

 

[Soundguy]

did you wire the alt as a 1 wire job or 3 wire job?

if wired as 3 wire, as long as the alt is spinning 400 rpm or so.. it should charge, and should automagically start charging as soon as it hits about 400 rpm, instead of needing the throttle gooseing.

soundguy

Hey guys,

I think I got this thing working! I finished fitting the new belt yesterday and wired the alternator into the system. The tractor started right up (although it would, given the new battery I had to buy), and there were no sparks, explosions, or shrapnel. Furthermore, there was a steady 15 volts across the battery terminals (most of the time - see below).

A few final questions:

- The pulley that came with the alternator was for a belt that was too narrow. So I pulled the pulley off the generator that was being replaced and adapted it to fit the alternator. However, that pulley was quite a bit larger in diameter than the pulley that was originally on the alternator, which means the alternator spins a bit more slowly than it would otherwise. And when the tractor is at a dead idle, there's only 12.5 volts across the battery leads. When I give it a bit of gas the voltage jumps to 15 and stays there. Does anybody think that's going to be a long-term problem?

- I'm not 100% convinced I got the wiring exactly right. The alternator "BAT" terminal goes directly to the positive battery terminal. According to the wiring diagram that came with the alternator, terminal "2" is also supposed to go directly to the positive battery terminal, so I wired "2" and "BAT" together. Terminal "1" is supposed to go to the output of the indicator lamp, which it does (although the indicator lamp itself is clearly busted - ordered a new one but it won't come in until later this week). There is no ground wire; I assume the alternator is grounded through its housing. Does the wiring sound right?

Thanks for all the help!

 

[jcalla]

I had an old JD lawnmower that used a generator similar to the one shown. I rewired it myself. It was also the starter and after the tractor started would switch over to generating DC current. Worked great for 18 years until hydrostatic trans went, then I traded it in for my 455.

JPC

 

[glenhenshaw]

Does anybody know how fast the engine should spin at idle? If I knew that I could figure out how fast the alt is going (and the right size for the pulley).

And does it hurt anything to spin the alt below 400 RPM?

 

[Soundguy]

nope.. just won't charge...

soundguy

 

[RickB]

Does anybody know how fast the engine should spin at idle?

Off the cuff, no less than 800 ERPM.

 

[jd110]

You might find that the alternator will work better after you get the new indicator bulb. With the broken bulb, the energizer circuit is open and it has to self-energize. That is the reason you need to rev engine to charge.

 

[Soundguy]

once it excites, it should stay charging down to 400 rpm though.

in any case.. 3 wire setup is best IMHO..

soundguy