490E stuck in rabbit

[Knivens894]

Gentlemen; I have a JD 490E that has decided to act up. The buttons to change the propel speed suddenly stopped working. It is stuck on the rabbit speed, which makes it difficult to climb grades without assistance from the stick. In addition the auto idle function has stopped working except when the manual pilot shut off is used. If anyone has had this issue before, I would sincerely appreciate any clues as to where to start to get this fault corrected.

 

[Bls repair]

Is switch working,power to switch

 

[Knivens894]

Please let me know which switch you are referring to? If you mean the auto idle switch, yes it is working. We checked the fuse and found it OK. I have been reading the operation and test manual which says the auto idle not functioning is an electrical issue with the system. I have printed out the test procedures for the propel pressure switch and harness as well as the propel speed pilot control pilot and harness. We will give those a go tomorrow. The switch for propel speed lights but does not change speeds for the propel function.

 

[Bls repair]

The rabbit turtle switch

 

[Knivens894]

The rabbit/turtle switch is working correctly. It will go up or down on command, lighting the various lights, but it does not actually change the speeds. Today we tested the propel pressure switches, both were open as they should be. The harness checked good at 5.1 V each. The propel speed control solenoid checks good. The output of the computer for propel checks good. Any ideas as to where the problem might be would be appreciated. It was working correctly until it quit.

 

[mikebramel]

Check the pressure at the motor which changes the displcement

 

[Knivens894]

What pressure(s) should I be looking for? Are they supposed to change from turtle to rabbit?