Hello, I've got a 490D JD '89 model and the electronics are totally inoperative. The machine is a bit slow and sluggish, but will still dig. The travelling and steering are weak. I would like some information on how I could "hot wire" the pump displacement solenoid using a toggle switch to ramp up pump output and pressure, while manually operating the throttle. My main concerns: do I apply the machine 24 V to one side of the solenoid and simply ground the other side to get full pressure, or do I have to drop the voltage/current down so I don't burn out the solenoid coil. I have no specs or data on what the ECU would actually apply to the solenoid when in power or rabbit operation. I have a JD shop manual, diagnosis and testing, but I do not have any solenoid coil info. Would anyone have any wiring diagram for this 490D? (Also, if someone knew what voltage/wattage the solenoid coil on the pump actuator solenoid would be...) Any or all input would greatly be appreciated!
The pump displacment solenoid only reduces flow by approx 10% when denenergized, hardly noticeable. I'll check my 790d to see if power or ground activates the solenoid. Have you checked pilot pressure?
Constant 24v to solenoid, ground controlled. The controller is pretty solid, if the wiring is all there and controller fuse is good, check the oil pressure switch, it sends a signal to the controller to tell it the engine is running, also controls the hour meter.
Thank you so much for the quick reply GregsHD. I will look up the pressure spec for pilot pressures when travel controls are used. I just purchased this machine and the wiring has had major tampering and I cannot get any of the modules or the cluster board to power up. All fuses are good...my main question: does the ECU supply total ground allowing 24V to the solenoid, or is the ground circuit pulse modified or only allowing 5 - 6 V to be applied to the pump activator solenoid? Also, I probably need a wiring diagram so I can trace every input and output, and repair as necessary. Then we will see if the boards fire up.
Should be the same wiring as my 790d, dash 1 Hitachi.. All my wiring diagrams are in the operation and test manual, funny how your manual doesn't have them. Doesn't explain how the modules function electronically though. My solenoids have 24v to one side constantly, ground the other lead and the solenoid functions, simple on-off solenoids.
Hello GregsHD, Thank you for the information and the diagrams! I am going to be working on this machine in a few weeks and I'll post how I made out. Thanks again for all your help.
I have a 490E which had a similar problem. I ended up calling the dealer for a mechanic. He found the CPU was dead. Upon checking the fuse to the unit was supposed to be 1 amp, but someone had installed a 5 amp in its place. The 5 amp allowed too much current draw and burned up a resistor in the CPU. I replaced the resistor and the fuse, then found out the angle sensor was the problem which had overloaded the CPU. First check the fuses to be sure they are properly sized and in good condition, then remove the CPU and open it up to see if there is a burned up element. Good luck!