Knivens894
Well-Known Member
I purchased a used 490 E about 6 years ago cheap. The engine ran well, everything functioned, but it was easy to stall in operation. I had the JD dealer do a service call for the stalling problem. He reported someone had installed a 5 amp fuse in the fuse block for the computer. The angle sensor was bad and the computer had been smoked. Those were replaced, it functioned better, but was easy to run hot hydraulically, so much so, that it could only run for two hours or so before it had to be shut down to prevent over heating damage. I went through every system, looking for the source of the heat, but did not find any. The machine failed sensors regularly, multiple angle sensors, DP sensors and pressure sensors. In the process, I learned the manual's specifications for sensors is totally outdated and do not apply even to JD supplied sensors.
I received advice from a number of people to sell the machine and get another one, "because this was a first generation computerized machine and I may never find the problem", but I am stubborn and refuse to let a piece of equipment beat me. The machine would also take out the computer fuse (1 A) from time to time. After going through everything, and I do mean everything, I considered rewiring the machine, but harnesses for the machine are not currently available. I used an ohm meter to check every wire, they all had continuity.
Drawing on a previous experience with defective wiring, I then used a meg ohm meter. The "megger" applies a high voltage (500-1000V) (using 2 "C" cell batteries) to the wire to test the insulation on the wires. CAUTION HERE: REMOVE ALL COMPUTERS BECAUSE IT CAN DAMAGE THEM. I tested all sensor leads to and from the computer with the megger and found no faults in any of them. When I tested the power into the computer from the fuse block, it was bad. It had a direct path to ground. I opened the harness and visually nothing appeared wrong with the wire. The wire was replaced. After removal, the old wire felt "crunchy" inside.
Long story short, the 3 feet of 18 Ga wire had been overheated by the idiot that installed the 5 A fuse where the one amp had been specified before I got the machine. The new wire to the computer increased the output from the computer to the sensors. They had to be readjusted. The low voltage to the computer had been causing the sensor failures and out of "normal" range indications to the computer caused the overload of the hydraulic system resulting in the machine overheating. It took me several years and more money to find this problem than I like to think about, but perhaps someone else can benefit from my learning curve.
I received advice from a number of people to sell the machine and get another one, "because this was a first generation computerized machine and I may never find the problem", but I am stubborn and refuse to let a piece of equipment beat me. The machine would also take out the computer fuse (1 A) from time to time. After going through everything, and I do mean everything, I considered rewiring the machine, but harnesses for the machine are not currently available. I used an ohm meter to check every wire, they all had continuity.
Drawing on a previous experience with defective wiring, I then used a meg ohm meter. The "megger" applies a high voltage (500-1000V) (using 2 "C" cell batteries) to the wire to test the insulation on the wires. CAUTION HERE: REMOVE ALL COMPUTERS BECAUSE IT CAN DAMAGE THEM. I tested all sensor leads to and from the computer with the megger and found no faults in any of them. When I tested the power into the computer from the fuse block, it was bad. It had a direct path to ground. I opened the harness and visually nothing appeared wrong with the wire. The wire was replaced. After removal, the old wire felt "crunchy" inside.
Long story short, the 3 feet of 18 Ga wire had been overheated by the idiot that installed the 5 A fuse where the one amp had been specified before I got the machine. The new wire to the computer increased the output from the computer to the sensors. They had to be readjusted. The low voltage to the computer had been causing the sensor failures and out of "normal" range indications to the computer caused the overload of the hydraulic system resulting in the machine overheating. It took me several years and more money to find this problem than I like to think about, but perhaps someone else can benefit from my learning curve.