Dang it. I needed the grapple today, hooked everything up and no reaction from the open and close rocker switch and I didn't hear the diverter valves operate like usual. There is +12v at the diverter solenoid (red wire) and +12v at each of the two black wires that follow the rocker switch operation.
Then I verified the valve assembly bracket is indeed grounded. It occurred to me the valves might be frozen up, it's been 3 or 4 months since I used the grapple. So I beat on the valves a little with a steel rod and ball peen hammer (access is a bit difficult) and no joy. I kept operating the switches hoping they would start working.
There is a connection block at the top of the valve assembly for the wires but after removing two screws the block wouldn't budge. I verified voltage with needle tips for my multimeter that punctured the insulation so I suppose there could be an issue under the block. I tried to measure the coil resistance with inconclusive results.
I'm going to call WR Long Monday but in the meantime does anybody have any troubleshooting advice?