John Deere MFWD 2355 Cab - Blown fuse issue

[sbeckwith]

Good Day All,
I am having an issue where the 20 amp fuse that sends power to the key switch blows intermittently. When it does blow, the tractor keeps running, lights still work, etc. The instrument cluster stops working and when the tractor is shut off, the key switch no longer supplies power to crank the tractor over to start the tractor up. Replacing the fuse allows it to start again and it may or not blow again the next time the tractor it used. I suspect there is a wire that is shorting while out in the field bouncing around, but I have no clue as to which wires draw power from that fuse. Is there anyone who may have access to an electrical diagram in order to figure out which wires to look at?

Details:
Fuse does not blow when starting the tractor
Fuse does not blow every time I use the tractor around the farm
Fuse blowing does not cause tractor to stop running
Fuse blowing does not cause running lights to stop working
Fuse is located in position #8 on the circuit board

Make: JOHN DEERE
Model : 2355 MFWD Cab Tractor
Year: 1998
Hours: 5562
Serial Number: L02355V632762
Thanks in advance for your help !
Steve

 

[jd110]

Fuse 8 powers the key switch as you know. The key switch then sends power to the starting aid switch(ether aid or manifold pre-heater), and to the fuel pre-heater switch if equipped. Key switch also sends power to fuse 9 which powers the entire accessory circuit. I would assume if accessory circuit had a problem, it would blow fuse 9 instead of 8. Key switch also sends power to start circuit relay, but since it does not blow when starting, I doubt that is problem area.

 

[sbeckwith]

Thank jd, It gives me a starting point to begin. I think I will replace fuse 9 with the correct fuse and see what happens. Right now, they were both 25 amp fuses installed in those locations, which according to the printed circuit board is incorrect. I may even just try pulling fuse 9 and see if fuse 8 holds up.

 

[Zebrafive]

You might try leaving fuse 8 at 25 amp and changing fuse 9 to 20 amp and see what happens. If fuse 8 continues to blow, that will rule out anything after fuse 9.

 

[Tx Jim]

Inspect the printed circuit board for poor connections as the boards have a long history of connection problems.

 

[sbeckwith]

Thanks everyone for helping me to work through this. I was able to get caught up on other chores on the farm and came back to this problem. I had the dash off so the fuse circuit board was exposed. I installed a new fuse and the tractor started right up. As soon as it started though, the fuse sparked and blew. This lead me to believe it may have something to do with the charging circuit. I had a couple of things to do on the farm that the John Deere was set-up to perform, so I did them since it was running anyway. Once done, I noticed the battery on the left side as your sitting in the cab was smoking, however, I checked the battery on the right side and it was fine. This has me wondering if the batteries are charged differently as I am thinking it has something to do with the charging circuits.

 

[sbeckwith]

I traced the wiring as far as I could without starting to remove the hood and other stuff. I seen no damaged wiring, so I pulled off the spade connector that goes to the "W" terminal on the alternator. I think this feeds the tach. I then pulled Fuse 9 and put a 10 amp fuse into fuse 8 (the only size I had left to work with) and just moved the key switch between acc and ign just to see if it would hold. It did, so I started the tractor up.... and it did with the 10 amp fuse in place. Now I am begining to wonder if the wire with a spade connector on that was plugged into the "W" terminal belongs there.

 

[Tx Jim]

This is the sender(parts key #2) for speed-hour meter on engine timing gear cover.

 

[sbeckwith]

Thanks Jim, but I am not sure I understand what you are trying to show me. Can the sender for the hour meter be causing my problem? Oh, maybe the black looking thing on the wire is the spade connector I spoke of above?

When I follow one side of Fuse 8 is seems to go directly to the battery/starter post. (+)
The other side seems to go to the starter switch.
Fuse 8 seems to feed:
- The Starter Relay Contacts and then to the Starter itself. (Have to have that circuit to start tractor)
- A fuse that leads to the neutral start switch thru to the coil of another Starter relay coil (Have to have that circuit intact to start tractor)

I keep looking at this thing and it's getting a bit frustrating for sure.

 

[Tx Jim]

I traced the wiring as far as I could without starting to remove the hood and other stuff. I seen no damaged wiring, so I pulled off the spade connector that goes to the "W" terminal on the alternator. I think this feeds the tach..

This statement of yours "feeds the tach" is the reason I posted the parts photo of the speed-hour meter sensor and I think it's not your tractors problem. One thing I remember from studying JD utility cab tractor service manual wiring diagrams way back when I was a dealer service manager is the wiring diagrams resembles a ""spider web"!!!!!!!!!