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I could use some help. My JD was running fine one day when I turned it off, then after about 30 minutes I went to restart, and it will not turn over, the 10 amp fuse blows (the fuse box has it labeled as "Timer"). When I replace the fuse I have dash lights, but when I turn the key it blows the 10 amp fuse. I appreciate any help.
 

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Sounds like you may have a short. Shorts occur for a variety of reasons. I would access the back side of your key switch and start checking for shorts there by using a meter. You might have a critter nesting and munching on your wires, which is a common cause of these types of problems. Look for signs of wire damage along the harnessing also...
Sincerely
 
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Are you referring to fuse "J" in the Operator's Manual which is labelled as Timer / Relay Unit?
 

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There is a short somewhere. On my 420 it would do this and the short was always inside the harness by the harness plugs between the key switch and starter. Try jumping for the back of the ignition and starter.
 

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Discussion Starter #5
I could use some help. My JD was running fine one day when I turned it off, then after about 30 minutes I went to restart, and it will not turn over, the 10 amp fuse blows (the fuse box has it labeled as "Timer"). When I replace the fuse I have dash lights, but when I turn the key it blows the 10 amp fuse. I appreciate any help.
Thank you,
Sounds like you may have a short. Shorts occur for a variety of reasons. I would access the back side of your key switch and start checking for shorts there by using a meter. You might have a critter nesting and munching on your wires, which is a common cause of these types of problems. Look for signs of wire damage along the harnessing also...
Sincerely
Thank you, yes, I plan to start checking each wire when I get back to the farm.
 

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Are you referring to fuse "J" in the Operator's Manual which is labelled as Timer / Relay Unit?
Looking at the fuse box, it's identified as "Timer", I have not been able to identify much information about this.
748970
 

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There is a short somewhere. On my 420 it would do this and the short was always inside the harness by the harness plugs between the key switch and starter. Try jumping for the back of the ignition and starter.
I will try that, I have a feeling the ignition may have something to to do with this problem. thanks.
 

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Could this timer be the glow plug circuit? Maybe check if the feed wire to the glow plugs has a short to ground. But pull that wire from the first glow plug before checking. Glow plugs have a very low interrnal resistance, and you might mistake that as a short. If you disconnect the wire, and measure resistance to ground, it should not be a low resistance to ground., If internal short in a glow plug is the problem, then the fuse should not blow with that wire disconnected.
 
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Could this timer be the glow plug circuit? Maybe check if the feed wire to the glow plugs has a short to ground. But pull that wire from the first glow plug before checking. Glow plugs have a very low interrnal resistance, and you might mistake that as a short. If you disconnect the wire, and measure resistance to ground, it should not be a low resistance to ground., If internal short in a glow plug is the problem, then the fuse should not blow with that wire disconnected.
No. I believe the glow plugs feed from one if the 80A fuses. If you look at the schematic that timer fuse (F3) feeds EVERYTHING.
 
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I'm trying to think what else the timer would be for. These newer tractors have a ton of electronics, for sure, so my logic may not apply. But my 20 year old little 4100 had a glow plug timer.
I don't have have a schematic, so if that's how JD has it wired, then agree, problem s elsewhere. But to me, the timer it self should be on a 10A fuse, and the timer would power a relay that would be fused from a larger (80A) fuse, to heat the glow plugs for the timed duration.
With this on-board computer stuff they have now, it may be completely different from what I'm use to.
 

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I'm trying to think what else the timer would be for. These newer tractors have a ton of electronics, for sure, so my logic may not apply. But my 20 year old little 4100 had a glow plug timer.
I don't have have a schematic, so if that's how JD has it wired, then agree, problem s elsewhere. But to me, the timer it self should be on a 10A fuse, and the timer would power a relay that would be fused from a larger (80A) fuse, to heat the glow plugs for the timed duration.
With this on-board computer stuff they have now, it may be completely different from what I'm use to.
The timer is just one of the components on the F3 fuse. It powers just about all the minor components.
 

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No. I believe the glow plugs feed from one if the 80A fuses. If you look at the schematic that timer fuse (F3) feeds EVERYTHING.
Could it be that the 10 amp fuse feeds to the glow plug timer and relay, and the 80 amp fuse is to the glow circuit itself? The electrical system isn't going to channel 80 amps through the switch; the switch would turn the timer and relay on or off, which would close when on and allow the much higher current to energize the glow plugs until the timer times out and shuts the relay. I'd look for an issue in the glow plug timer or the glow plug relay, which the timer controls.
 

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Could it be that the 10 amp fuse feeds to the glow plug timer and relay, and the 80 amp fuse is to the glow circuit itself? The electrical system isn't going to channel 80 amps through the switch; the switch would turn the timer and relay on or off, which would close when on and allow the much higher current to energize the glow plugs until the timer times out and shuts the relay. I'd look for an issue in the glow plug timer or the glow plug relay, which the timer controls.
Yes, that is pretty much how it is. It appears fuse F3 is what they label as "timer". In my 2720 Operator's Manual it is called "Fuse J" but in the Technical Manual it is "Fuse F3". No confusion factor here. :)

Below is part of the schematic. JD breaks their schematics into so many pieces it's hard to get a "big picture" of the circuit.

749026
 

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Since the OP is dealing with a condition that keeps blowing a fuse, it might be a good idea to invest in a short circuit tester.

749031
 
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Wow! been a while since I've seen one of those! And never in that good a shape and analog.

Allen
That image is from Amazon. You can buy them brand new. :)
 
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Discussion Starter #17
Great information, I appreciate the advice. I am currently looking into buying a technical manual for the 2720 (it will not be from JD, I was quoted over $300). In the mean time, I can start looking for shorts in the A1 Preheater and M2 Fuel pump circuit. I will also look into the short circuit tester too.:)
 
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