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

[glenhenshaw]

Hi all,

I have a John Deere 820, serial number 065272L. I've owned it since 2005 and have used it sparingly. For several years now I've known it had a problem charging the battery. I'd put a new battery in it and it would start 5 or 6 times, and then I'd have to start jumping it; after ten or twelve more starts that wouldn't work either, since the car doesn't really provide enough current to turn the JD starter, so I'd put a new battery in it.. Since I only use it five or six times a year, this system worked okay.

But this week I couldn't start it for anything and so got serious about fixing it. At the suggestion of my local JD dealer (really small place in southern Maryland) I pulled the alternator and took it in to be tested. And... lo and behold, it looks for all the world like it's a six volt alternator; it even says "6V" on the service plate. Which explains why it won't charge a twelve volt battery, but leaves us with a couple of bigger mysteries. First, the alternator looks nothing like the alternators shown on the various OEM parts supplier websites for this tractor. Second, how and why did anyone get a six volt alternator that actually fits - there are no apparent modifications to the tractor to make the alternator fit - and install it in what is clearly a twelve volt electrical system?

The JD mechanic, who in my experience is very good, is scratching his head. He's afraid to order a replacement OEM alternator since they all look different from the one that came off the tractor, and can't figure out how you could even find a 6V alternator that would randomly fit the wrong tractor.

Any ideas?

 

[kuboman]

Is it a 6volt alternator or generator. I have never heard of 6 v alternators but most old tractors had generators.

 

[glenhenshaw]

Is it a 6volt alternator or generator. I have never heard of 6 v alternators but most old tractors had generators.

Errmm... dunno. How do you tell the difference? I'm pretty good with my hands but have no mechanics experience.

In looking at pictures the external appearance of the part I removed looks like a generator (it's fairly long with respect to its diameter, and it has a front mounting plate with two offset bolt holes and a rear mounting plate with one hole). However, the parts websites all list alternators, not generators, for this tractor.

When did JD switch from generators to alternators? I think my tractor was built in 1971. And did the older 6v generators have the same mounting points as the 12v generators did?

 

[jd110]

The 820 shows a generator for serial numbers up to 075344 and an alternator for above that number. They are both 12 volt and both are made buy Robert Bosch. I attached a parts diagram for both versions. Can you post a photo of your generator/alternator?

 

[glenhenshaw]

What I have is clearly the generator...

 

[glenhenshaw]

So would a six volt generator fit in the same spot? And do I need a new voltage regulator as well as a new generator?

 

[jenkinsph]

glenhenshaw,
Looks like somebody stuck that 6v generator on there before they sold you the tractor.

I would get the proper generator and check the voltage regulator to see what it is. I would be inclined to change both to eliminate damage to the new generator.

I would heed the advice you get from jd110 an experienced Deere mechanic.

 

[tommu56]

unless you need the correct part i would put a 10-SI alternator in it looks like the one in the right in the pictures some one else posted

here is a link on how to install and wire one

Wiring up the GM 10SI Alternator

and another

Catalog

and one more

The Delco 10-SI and 12-SI Alternators

 

[Tx Jim]

unless you need the correct part i would put a 10-SI alternator in it looks like the one in the right in the pictures some one else posted

I'll second installing a Delco alt. as long as there's enough clearance under the hood.

 

[glenhenshaw]

I'll second installing a Delco alt. as long as there's enough clearance under the hood.

This is great, guys, thanks. That sounds like the best idea. I have a fair amount of electrical experience so I'm pretty sure I could wire it in. But I'm worried about physically mounting it. Does anybody know whether a Delco alternator will fit on the same mounting holes as the original generator? Otherwise, does anybody know how involved the required modifications are?

 

[kuboman]

This is great, guys, thanks. That sounds like the best idea. I have a fair amount of electrical experience so I'm pretty sure I could wire it in. But I'm worried about physically mounting it. Does anybody know whether a Delco alternator will fit on the same mounting holes as the original generator? Otherwise, does anybody know how involved the required modifications are?

You may get all the mounting parts through JD or try a tractor wrecker. It was common practice years back to convert these older tractors to alternators.

 

[tommu56]

Google the s10 on flebay some have some brackets with a retrofit kit
but 4 pieces of angle and a piece of flat stock welded or bolted together.

Uni BRACKET & 12-volt Delco 10SI ALTERNATOR 63-amp | eBay

Universal bracket & 1-wire Delco 10SI

 

[jenkinsph]

Assuming you are referring to the single wire alternators (had forgotten about that) I agree if it fits go for it.

Might compare the Deere OEM alternator brackets to the Delco alternator. Just thinking you may be able to buy the brackets that fit without a lot of fabrication.

Didn't see the last two posts before answering.


I will try to get you an up close picture of the alternator setup on my 820, which is a late 73 model.

 

[RickB]

You may get all the mounting parts through JD or try a tractor wrecker. It was common practice years back to convert these older tractors to alternators.

All well & good except this tractor was factory fitted with an alternator.

No more trouble than it is to wire, I'd connect the Delco as a non-self-exciting (3 wire) alternator. Far more reliable charging and will make use of the existing charge indicator lamp that will tell you when the system is working.

 

[mrpoppy58]

Is it a 6volt alternator or generator. I have never heard of 6 v alternators but most old tractors had generators.

To find a 6 volt postive ground Alternator try Quick Start High Output Alternators. 616-606-5045.
Poppy

 

[RickB]

A 6 volt alternator is not the solution here. Amazing how folks hurry to post without understanding the problem, or apparently even being familiar with the machine in question.

 

[jd110]

I agree with the majority here. A Delco alternator is definitely the lowest cost alternative here. It has a built in regulator, so you won't need to buy that also and they are so widely used, they are very inexpensive. The generator you pictured is a Delco. I can't really answer how to fit it up, The mounting bracket you now have may not be original since the generator is not correct. The best thing would be to get the alternator and see how close everything is to aligning. Sometimes very little or no modification is needed to mount.

 

[mrpoppy58]

A 6 volt alternator is not the solution here. Amazing how folks hurry to post without understanding the problem, or apparently even being familiar with the machine in question.

I did not say it was the solution here. Some one might be interested in a 6 volt Alternator. Just trying to be helpful. When I started working in Garages in 1959 there were lots of 6 volt positive ground systems around. I am VERY familiar with Machines. You are right some people are very quick to post on here. Some People seem to know more than others. Have a good Day.

 

[glenhenshaw]

I agree with the majority here. A Delco alternator is definitely the lowest cost alternative here. It has a built in regulator, so you won't need to buy that also and they are so widely used, they are very inexpensive. The generator you pictured is a Delco. I can't really answer how to fit it up, The mounting bracket you now have may not be original since the generator is not correct. The best thing would be to get the alternator and see how close everything is to aligning. Sometimes very little or no modification is needed to mount.

Well, the generator *says* "Wilson" on it, although I can't find mention of a Wilson OEM parts manufacturer anywhere. In any case it doesn't look like either the tractor or the generator has any alterations to make it fit. The mounting points on the generator match perfectly with the mounting points cast into the tractor's engine block.

However, it also looks like the Delco generator (somebody?) linked to on ebay has a bracket that matches. So I think I'm going to try that. Even if it doesn't, the picture of the bracket gives me an idea about how I could build one with the right dimensions.

Anybody want a 6v generator, slightly used?

 

[glenhenshaw]

Okay guys, I ordered a Delco alternator and a universal bracket. Got the bracket assembled correctly, replaced the pulley, and fitted the entire thing in the tractor. But that leads to a problem I don't know how to solve: the alternator is fatter than the old generator was, and I can't swing it in towards the engine block far enough to get the belt around the alternator pulley. The case of the alternator hits the engine head. I assume this means I need to install a longer belt, right? But how do I do that? As best I can tell I'll have to drain and remove the radiator in order to get the belt around the fan pulley.

Does anybody know what the procedures are for this? Or where I can buy a JD 820 service manual?