Burning fan belt on JD 870 - MyTractorForum.com - The Friendliest Tractor Forum and Best Place for Tractor Information
 
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post #1 of 4 Old 05-25-2019, 04:48 PM Thread Starter
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Exclamation Burning fan belt on JD 870

This is my first post here, and I'm hoping for some help and advice.

My 870 is a 1995 or 96 model. It's been back from dealership service for about three weeks, and I know they replaced the fan-alternator-water pump belt then. It's been running like a champ, but the charging system problem light was on when they got it and when they returned. It's been on for maybe eight or ten months, but the tractor didn't seem to be bothered by whatever it was diagnosing--and I did buy a new battery which was needed.

I have used it for hours mowing pastures, and all was well--until yesterday. I cranked it up and smelled something burning. Turned it off, cranked it up again and saw smoke and turned it off. Now my full attention was on what was going on, so I lifted the hood and cranked it up yet again, There was smoke coming from the left side of the engine compartment; the newly replaced fan/water pump/alternator belt on the pulley in front of the alternator was smoking and actually bubbling.

I have followed instructions and loosened the belt; but what that is supposed to tell me I do not know. I have a suspicion that it may the water pump, but it could also be the alternator, since that is where the belt was melting.

Might y'all be able to give me any insight into this problem. I will add that I have the Technical Manual and a Shop manual for this tractor, and they seem to be quite useless.

I'm a lumberjack, and I'm okay.
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post #2 of 4 Old 05-26-2019, 12:01 AM
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Re: Burning fan belt on JD 870

Just a SWAG, alternator bearings gone or going .... or the alternator is dead or output is shorted somewhere. I have a 650 and 770 and the wiring to both alternators is marginal. Melted at the connectors on both.

Yours could have melted and shorted in the harness.

Disconnect it (connectors in the harness on the other side of the engine) and see what happens when you start it. If the issue goes away - you've got a short or loading problem down stream of the connector.

It may turn freely at low rpm (by hand) but loads up at anything above idle if shorted. Take it off - your local autoparts guy should be able to test it.

The charge light should not be lit ... it indicates a problem somewhere in the alternator, charging system, or both. Your dealer should have found the problem and fixed it. It's a very simple circuit - not rocket science. Your new battery will eventually go dead - maybe damaging the battery in the process if it gets pulled down low enough.
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post #3 of 4 Old 05-26-2019, 10:25 PM Thread Starter
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Re: Burning fan belt on JD 870

The alternator is bad, that's the problem. It's frozen solid now.

Now for advice on where to buy a new alternator. I can get a JD one for something like $350 with a $50 core charge. I can get a German manufactured one that is sold by Hoye for Yanmar/JD tractors for $135+. I can get a JD reman for $285 after core charge. Or I can get one from DB Electrics for $57+ with a 1 year warranty. I could buy 6 of the DB Electrics one for 1 JD or 2 and a bit of the Hoye ones.

I'm tempted by the idea of German quality, but there is a $17 shipping charge from Hoye.

Do you think that buying the cheap one would be a bad idea in the long run?

I'm torn that the JD place didn't catch it. They'd have done the JD replacement at JD prices, so I'm glad that they didn't. On the other hand, they really should have caught the problem, since I did ask them to check out the alternator when I took it in. They obviously didn't, but probably forgot it among the list of things to be fixed.

I'm a lumberjack, and I'm okay.
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post #4 of 4 Old 05-27-2019, 12:58 PM
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Re: Burning fan belt on JD 870

Great - at least the problem is obvious.

My first reaction is to take it to a local alternator rebuilt shop and get a cost estimate to fix what you have --- or just take it apart and see whats wrong. Most likely bearings. Not much to these little alternators these days. Bearings are cheap from Grainger - local Auto Zone will rent you any special tools you might need - bearing pullers etc.

Repairing what you have lets you keep the basic OEM device, ensuring everything fits up as it should after it is fixed. Most local shops offer some kind of a warranty so there is some recourse if they get it wrong for some reason. Again it's not rocket science - just a magnet and a coil. I've had real good luck with letting local shops rebuild devices like this - Having a tech working one to one on it is far better than a factory assembly line - anywhere!!

I've purchased a few parts from both Hoye & DB - quality has not been an issue. Personally, given the small effort required to install it and non critical nature of the device, I'd give the $50 one a try - what have you got to lose? If you don't want to ever mess with it again - give Hoyle a try. I'd bet a weeks pay JD buys from the same vendor as Hoye but has them painted green! That green paint is extremely expensive - if you haven't noticed already!

Lastly, I'd go back to your JD dealer and ask for new belt -- at the very least - the only way to straighten these guys out, is to make them pay for stupidity. But you're right - if they had been smart, they would have sold you a new alternator at list price - plus a new belt and labor - consider yourself lucky!!

But it's not just JD, Beechcraft tried to charge me $2000 for a fuel tank cap!! (They make JD look like pikers) Fixed it (legally) for $50 - with a little help from my friends on the internet. ($5 gasket)

One more thought - There are several very good tractor savage yards around. Bet Western Kentucky Tractor Parts (https://wkytpstore.com/) has a good, serviceable OEM alternator on the shelf. Good guys to work with - I rolled my 770 and broke it clean in half - they sold me all the castings and parts I needed to put it back together for very reasonable $$$. Major parts for these older tractors are getting harder to find. They are good folks to know!!

Take care & gud luck!!
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