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John Deere Tractors Discussion Forum
Show Parts for Model:

1971 4020 alternator replacement

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J Colyn

02-23-2010 22:55:53
209.91.107.250



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12V motorola alternator with attached voltage regulator quit charging on my father-in-law's late 4020. It's still being used everyday feeding cows and we decided there's no time to take the old motorola in for repairs. Plus, it's a lot of driving back and forth to his place so I bought a replacement from deere to bring out. They sent a delco replacement (SE501386 - about $320 on sale) and looks like it needs to be wired slightly differently than the motorola. Right now, on the tractor wiring harness there's a purple and a orange wire going to a connector that hooked up to the same colour wires on the motorola regulator harness.
I'm looking at the wiring diagram I have for the delco alternator from the 6030 section in the I&T JD203 shop manual. That's all I've got, my JD SM covers the early model and the I&T has nothing for the late 4020 alternator other than specs. It shows orange going to orange and then to terminal 1 on the alt. The purple wire doesn't look like its used at all. Then the wire from alt terminal 2 is hooked to the alt battery terminal along with the red and black wire from the tractor harness.
Does that sound right? JDparts.com is no help this time. If someone has a JD SM for the late 4020's, could they check how the delco is wired? I'm mostly worried about that purple wire shown not being used. Plus, I really don't want to wreck the new alternator. Thanks, guys

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Ray

02-24-2010 14:35:04
71.48.73.114



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 Re: 1971 4020 alternator replacement in reply to J Colyn, 02-23-2010 22:55:53  
Some of those motorola's you can't get parts for anymore and cost more to repair than you can buy a new GM alternator.We have probably replaced 5 of them over the years.



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J Colyn

02-24-2010 13:14:51
192.197.71.189



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 Re: 1971 4020 alternator replacement in reply to Ray Tellin, 02-23-2010 22:55:53  

Bob said: (quoted from post at 15:01:08 02/24/10) Pulley would be $15 to $30 at a local auto electrical shop!


Actually I wasn't too ticked about the pulley price, they gave me a double pulley instead. The single pulley listed at about $150. ErK!
I got a new pulley on my 24V generator from the rebuild shop I should have gone to in the first place, seem to remember it was around $40-50.

Everything seems like more money in Alberta, just wondering what deere in the Dakotas (Bob?) has that SE501386 alternator listed for?

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Bob

02-24-2010 22:48:14
69.178.228.68



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 Re: 1971 4020 alternator replacement in reply to J Colyn, 02-24-2010 13:14:51  
Part Details
Part Number: SE501386 Part Price: 317.10 USD
Core Value: (15.00 USD)
End Price With Core Return: 302.10 USD



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J Colyn

02-24-2010 08:19:04
192.197.71.189



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 Re: 1971 4020 alternator replacement in reply to J Colyn, 02-23-2010 22:55:53  
Thanks Bob and Mike,

I agree with you Bob, hindsight is 20-20. What I should have done is take the old motorola with me to a repair shop. I did talk to a shop I've used before and in the worse case scenario it could have been redone for $200.
Bob (the father-in-law) does have a Case to use for feeding cows but prefers the 4020.

I was surprised to see a Delco show up, I thought it would be another motorola. But I ordered it, so no returning it. Plus it didn't come with a pulley, and the old one wouldn't fit, so there's another $50.

The motorola did have the regulator mounted right to the back of the alternator, so I wonder if that harness will work.

I hate splicing wires so I'll check it out.

Maybe I should get a SM for Bob's 4020 too.

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Bob

02-24-2010 13:01:08
69.178.228.68



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 Re: 1971 4020 alternator replacement in reply to J Colyn, 02-24-2010 08:19:04  
Pulley would be $15 to $30 at a local auto electrical shop!



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Mike Aylward

02-24-2010 04:27:40
216.145.134.216



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 Re: 1971 4020 alternator replacement in reply to J Colyn, 02-23-2010 22:55:53  
J, a quick and easy fix without having to do anything to the wires is to go back to your dealer and ask for an adaptor harness for a 7520 to convert to a Delco alternator. This adaptor plugs right into the factory harness on your tractor and will plug into a Delco without doing any cutting or splicing whatsoever. It makes a neat installation. I have one on my late 4020. Hope this helps. Mike

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Bob

02-24-2010 04:36:19
69.178.228.68



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 Re: 1971 4020 alternator replacement in reply to Mike Aylward, 02-24-2010 04:27:40  
That harness is AR55283 ($17).

Will it connect up to the tractor harness on units with the regulator NOT mounted directly to the Motorla alternator?



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Mike Aylward

02-24-2010 14:44:37
216.145.134.216



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 Re: 1971 4020 alternator replacement in reply to Bob, 02-24-2010 04:36:19  
Bob, I do know the harness is a direct fit for the '71 and '72 4020's (250,001 and up). I am not sure about the '69's and 70's due to their different wiring. Mike



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Bob

02-24-2010 03:35:10
69.178.228.68



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 Re: 1971 4020 alternator replacement in reply to J Colyn, 02-23-2010 22:55:53  
WHY didn't you just get a Delco from an auto parts store and save about $280.00?

Bottom line is... Delco's #2 terminal (voltage sense) can be jumpered over to the large output stud.

Find the wire that originally went to to Motorola regulator that is fed through the "idiot light" and connect it to the Delco's #1 terminal.

That wire will only be "hot" when the key switch is "on" and when that wire is shorted to ground the "idiot light" will come on.

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