I am getting an error code 15 for the pump contactor. When I manual close the contactor the hydraulic pump works fine. I replaced the contactor but I still get the same error code. The voltage at the contactor coil is around 21 volts which I thought was kind of low for a 36 volt system. Does anyone know how the master or slave controller engage the contactor coils? I am assuming some kind of BJT NPN transistor with a flywheel diode across the coil. If anyone has a portion of the wiring diagram that shows the contactor coil driver I would appreciate taking a look at it.

I found out that my SC4000 uses a GE IC3645SR3R404P3 controller(s). http://fsip.biz/Documents/CR1%20Tech.pdf

Now I just have to figure out why the controllers contactor driver for the lift pump causes the contactor to flutter. Possibly sensing an over current condition in the contactor coil?