L785 won't crank

[scotte6]

I have a 785 with the perkins diesel, not sure what year. The engine will not crank unless I flip the switch on the control module. I jumped out the seat and seat belt switch for testing purposes, still no crank. With both of those switches jumped, and the key on I only get 3 LED's on the control module (timer, seat, & belt). Owners manual states that the SOL LED should be on as well. If I flip the switch to "service" it will start right up, but of course none of the hydraulics will work. Any suggestions? Thanks Scott

 

[Mike10]

The seat switch harness contains a diode. If you remove the connector from the seat switch and jump across the harness terminal there you are ok, but if you unplug the harness at the connector at the front of the seat and jump there the system will not work...........The sequense also needs to be correct for the system to work. First sit in the seat, fasten seat belt and then start.......Since the seat, belt and timer light are on, I would assume that part of the circuit is working. The sol comes on when the ign key is turned to the on position......You need to disconnect the connector from the bottom of the module and check if you get power at one of the terminals when the key is turned on......If no power then you need to check the wiring and ign switch......If you have power, then the module may be bad. There will be more terminals with power, you need to find the terminal that powers up when the ign switch is turned to the on position.

 

[scotte6]

The seat switch harness contains a diode. If you remove the connector from the seat switch and jump across the harness terminal there you are ok, but if you unplug the harness at the connector at the front of the seat and jump there the system will not work...........The sequense also needs to be correct for the system to work. First sit in the seat, fasten seat belt and then start.......Since the seat, belt and timer light are on, I would assume that part of the circuit is working. The sol comes on when the ign key is turned to the on position......You need to disconnect the connector from the bottom of the module and check if you get power at one of the terminals when the key is turned on......If no power then you need to check the wiring and ign switch......If you have power, then the module may be bad. There will be more terminals with power, you need to find the terminal that powers up when the ign switch is turned to the on position.

Success! Thanks so much for your help. I hooked the seat switch back up and it started right up. I was not aware of the diode, thought I could just jumper it out. Your help is much appreciated!