JD 870 will not start...

[JS415]

JD 870 will not start...UPDATE>>>REPAIRED!!!

Greetings,

I have not posted here in ages, because of no issues with my tractor. This morning, that all changed.

I went to start the tractor, and it turned over 2, maybe 3 times then the battery went dead. It slowed cranking to a crawl, until it would not turn over at all. The battery has needed replacing all summer, but I have been putting it off.

I decide to jump start it so I could finish a small job I needed to do. Jumping would not work. I could turn the key, but nothing happened. I had lights, hazards, etc. but would not turn over.

I also did not hear the usual "click" from what I assume is the fuel solenoid. Dead as a door nail.

I searched here and found this thread: https://www.tractorbynet.com/forums/john-deere-owning-operating/126772-jd870-will-not-start-2.html

Using this info, I started searching.

First thing I did was to go buy a brand new battery.

Next I checked for voltage at the starter, on the larger wire running from the battery. I had a good 12V at this point.

Next I tried checking for voltage on the smaller wire on the solenoid. With the new battery in, and key in "crank" position, I had no voltage on the small wire.

Next, out of desperation, I jumped between the starter and solenoid. The tractor cranks and cranks, but will not start.

Keeping up my search, I found a blown fuse in the fuse panel. The leftmost 3A fuse was blown. No idea why.

I replaced it, and now when I turn the key on, I hear the familiar "click" of the solenoid. But no start. Still 100% dead trying the key.

I do now have 12V on the smaller starter wire after replacing the fuse.

Back to my jumper, with the key on, a barely touch the starter with my jumper, tractor started, and has been running fine all day.

Just turned it off, and completely dead. Something has broken or another fuse blown maybe? Some sort of safety relay gone bad?

Anybody have any ideas on what I might try and troubleshoot next?

Thanks,

Jerry

 

[Spindifferent]

I just replaced the rotary (ignition) switch on my JD 3520 after having similar electrical symptoms - with one big difference in that the switch was physically broken. The key just turned freely and completely around in the switch.

It seems like the rotary switch is a common part used over many years and models. You can likely find it easily. Here's the part number for my JD 3520. Not sure if it the same for your unit.

Rotary Switch
Part Number LVA21501
Description
ROTARY SWITCH,IGNITION,KEY,4-POS

 

[super55]

Can you post a pic of where you are running your jumper wire to the starter. Sounds like you might be jumping the posts on the starter solenoid. If it's the solenoid can try tapping lightly on it with a hammer to see if it will engage or if it is rusted around it clean it up so it grounds better to the engine block.

Not real familiar with the layout of the 870 so a pic would be a huge tool to help diagnose.

 

[zzvyb6]

Ebay: "DENSO STARTER SOLENOID REPAIR KIT CONTACTS". Been there, this fixed it. Get the appropriate kit for your starter. Easy to fix. Kinda difficult to remove the starter. There's 1 bolt that is nearly impossible to back out.

 

[JS415]

After thinking about this issue all night, I started going back over everything I had done in my head. After finding and replacing the 3A fuse that was blown, I had 12V on the small wire that connects to the solenoid, but still would not start.

However, when I jumped the solenoid to the constant 12V on the starter, it fired right up and ran fine. This did not make sense, since 12V is 12V regardless of where it is coming from.

The solenoid works when jumped, but not when connected to the wire with 12V????

When I woke up this morning, I walked back outside to look things over again, and my suspicions were correct. After I replaced the blown 3A fuse, I had forgotten to connect the small wire back up to the solenoid. So even though I was sending 12V from the ignition to the solenoid, it would not start because "somebody" forgot to hook the wire back up......

So my only issue now is why was the fuse blown. Maybe just a fluke, or did something cause it to blow. I bought several extra, and am keeping my jumper wire on the tractor just in case.

Anybody know what the 3A fuse is for? The legend on the fuse cover shows it as a fuse for the PTO. At least that is what the little diagram looks like.

Thanks for the advice and tips.

Jerry

 

[Industrial Toys]

All I know, is that when one has a failing battery, do yourself a favour and replace it or you could have all kinds of other problems crop up.

PTO may mean the safety circuits. I once had a small fuse, I think for the safety circuits) fail inexplicably on my 770 (same era of machine/yanmar). It was well hidden, but when replaced it never gave trouble again.

 

[grsthegreat]

As a battery starts to die, a circuit needing so many volts to operate will try harder to pull the needed voltage, and amps will increase, blowing fuse. See if new battery eliminates the issue. Also, lower amp fuses would blow first.

 

[Industrial Toys]

If I remember correctly, I don't think my fuel solenoid operated when my fuse had blown. So maybe different fuse. But I'm guessing those machines won't start with a PTO engaged.

 

[grsthegreat]

Here we go again with the myth, and from a retired electrician no less. :confused3:

https://www.tractorbynet.com/forums...-issue-jd-5210-a-post5300387.html#post5300387

not a myth. Ive seen it happen. Dont really care what people say. Ive experienced it in the field. Replaced battery and issues went away. So you tell me why

As a case in point. One of the testing factors listed in Generac Service Manual on an older series of generators had a inline 15 amp glass fuse in control panel. If it kept failing one of the tests was to replace battery.

 

[grsthegreat]

You and I got into this once before, and I suspect that you never read the link I posted, either now or in the past. As to your Generac example, yes I can offer an explanation, but why bother? After all, you don't care what people say. You're the NEC Code Man. Also, when you experience these mythical occurrences, what kind devices were you feeding?

Whatever, all i can say is ive seen it occur. I did read your link. Dont know what to say. I can tell you that i have swapped out batteries on the generators blowing fuses and i never got a call back. Can you explain that? Could be the op here had a old, weak fuse that gave up the ghost when battery failed. He did say it was working up to the time battery failed. Lets just see what happens.

 

[grsthegreat]

You and I got into this once before, and I suspect that you never read the link I posted, either now or in the past. As to your Generac example, yes I can offer an explanation, but why bother? After all, you don't care what people say. You're the NEC Code Man. Also, when you experience these mythical occurrences, what kind devices were you feeding?

by all means, lets hear your explanation about the generators. There the only 12 volt systems i have much experience with. Everything else is high voltage. Dont work with autos much.

Im always open to hearing about better ways to fix something. When you stop learning ... that means your dead.

I dont know why you think im closed minded about this theory. Im just stating what i have found in the real world.

 

[Fuddy1952]

Re: JD 870 will not start...UPDATE>>>REPAIRED!!!

As a retired 43 years electronic technician I believe electricity is one of the most difficult things to understand, probably because you can't see it.
All I did was troubleshoot and yes I've seen plenty of weird unexplainable things, but it all boils down to ohms law, like this cartoon demonstrates.
Electricity is easier to understand if you relate it to water. Battery is the storage tank, generator or alternator a pump, wires are pipes.
Voltage is electrical pressure.
Current is volume.
Ohms is resistance.
A small thick wall pipe can carry lots of pressure but not much volume. (Like spark plug wires).
A big pipe, lots of water volume just like why the battery to starter wire is so big.
Resistance like a bad connection is like a restriction in the pipe (or wire), so voltage (pressure) tries pushing current (volume) through.
When voltage (pressure) goes down current (volume) also goes down. Same with resistance. High resistance creates a voltage drop. High voltage like spark 1,000 ohms doesn't mean much since current isn't high. A starter circuit 1 ohm is a lot because 12 volts is trying to push 200 amps or more.
The battery is for starting an engine. Once started the generator or alternator takes over. The battery isn't needed anymore since engine runs the pump.
This is over simplification but maybe it helps understanding.View attachment 677334

 

[Fuddy1952]

Re: JD 870 will not start...UPDATE>>>REPAIRED!!!

.

 

[Industrial Toys]

One day if I have my scanner out, I should post a "Fairchild Semiconductor" Article on designing automotive power supplies and all the mayhem, spikes, collapsing fields and so forth that goes on in the average automotive electrical system.

Makes me wonder if my chance the OP boosted and ran his JD without a battery.

 

[fried1765]

Re: JD 870 will not start...UPDATE>>>REPAIRED!!!

.View attachment 677346

LOVE IT !!!!

 

[JS415]

Makes me wonder if my chance the OP boosted and ran his JD without a battery.

Thanks for all the comments and ideas. I've never had to jump it off, or ran it without a battery. When the battery was too low to start, I would just put a charger on it for an hour or two and fire it right up.

It cranked just fine, although only about 3 times, the morning it quit. Only after the battery was completely dead, did it not start. That has to be when the fuse blew. Too low of a voltage, or too much strain on the battery, and the weakest link let go? It was only a 3A fuse, the lightest fuse in the box.

It was just sitting int he barn, so I was not running or operating the PTO.

I'm just glad it's fixed and ready to go. I've got about 5 acres that need to be mowed pretty soon......

Thanks,

Jerry

 

[grsthegreat]

What happened to K7LN. his post disappeared. I was wanting to hear his ideas as to why my real world experiences were wrong.