Need help with my x740 mower - won't start / burnt diode

Bennet89 · Jun 22, 2023

Hey everyone,

I'm facing a problem with my x740 mower and could really use some advice. Here's what's been happening:

Earlier this year, when I tried to start my mower, only the dashboard backlight came on when I turned the key. After some investigation, I discovered that one of the 15A diodes/fuses (the 15amp fuse that is the 2nd one down) was faulty. I replaced it, and the mower worked fine for the next two uses. Link to image - the blown out fuse is removed in blue circle

However, today I encountered a new issue. It was a very hot day, although I'm not sure if that's relevant. When I tried to start the mower, the dashboard lights came on as usual. But when I turned the key further to run the motor, the entire dashboard went off. Upon inspection, I found that the same diode had failed again. In my impatience, I swapped it with a new one, but as expected, the diode burned out without a successful start. It seems like too much current is running through it.

Now, I'm seeking advice on how to tackle this issue myself. Is there something I can do to fix it? I would appreciate any suggestions or guidance you can provide.

Thanks in advance for your help!

oldnslo · Jun 22, 2023

My suggestion to either purchase the service manual for your X740 or talk to your dealer to see if they will print out the electrical wiring diagram. Then use this to start tracing the circuit(s) looking for the source of of the over load.

beenthere · Jun 23, 2023

Fix up a 12v light bulb to a blown fuse and insert into the slot. If short, then the bulb will be lit and stay lit until you find the cause of the short. Methodically disconnect wires, and/or move them around to get the bulb to go off.

Jims1025R · Jun 23, 2023

I suggest immense caution with this! I had a diesel X740, and I really liked it. It had the same problem, and I replaced that fuse several times, without ever really figuring out what the problem was. I only traced it to a computer problem, because there was no physical wiring problem I could find. Ultimately, the tractor spontaneously caught fire one night. That was a problem, but worse, it was parked in the back of my airplane hangar, so that fire cost me the X740, a JD650, a very nice Cessna, a Polaris 6x6, and a lot of other stuff I appreciated. My error putting all my toys away for the night!

Based on very sad experience, and poor thinking on my part, I suggest that until you are 100% certain the problem has been correctly repaired, you not leave the tractor anywhere where it poses a fire threat to anything else. Or... disconnect the battery every time you're finished with it!

Bennet89 · Jun 24, 2023

I've inspected most of the cables and noticed that one of them had a damaged coating and most of the conductor wires were also damaged. This particular cable is situated near the rear PTO, which the previous owner had removed when I purchased the mower. The wire adjacent to it also displayed some signs of damage, with a slightly crumpled insulation layer. It's likely that I hit something there, or perhaps some critter had a little too much fun.

I dealt with the problem by cutting off the defective sections of both wires and then reconnecting them, twisting the wire ends together, and sealing it off with electrical tape (img link) Admittedly, this is a temporary and somewhat crude fix, but it did the job. The motor managed to start up without a hitch twice yesterday and twice again today.

However, I'm not entirely confident that this was the root cause of the issue - it could just be a coincidence. Given that I've had starting troubles for most of last year and fuse issues this year, I'm going to stay vigilant. The other issue I discovered were a couple of wires under the seat that were being pressed against some metal by a plastic tie. I've loosened that tie - the insulation looked more or less intact, but it was extremely tight, so perhaps that was contributing to the problem.