Solenoid valve on dump truck intermittent

[Welder Dave]

Wondering if anyone has experience with troubleshooting electric solenoid valves. I bought a 94 Ford L9000 that was a former plow truck but now only has the dump box. It has a Rexroth solenoid valve operated from a joystick switch in the cab. All the other functions have been disconnected. The problem is the hoist is intermittent. Sometimes it works great or only takes a couple tries and works fine but other times it can take a dozen tries to get it to work. I talked to one place familiar with Rexroth valves and they said the solenoids are wet and can get gummed up and not work properly. I have tapped on the solenoid with a plastic handle screwdriver and got it to work but it may have been a fluke and just decided to work on its own. Maybe it could be a switch problem too? If I unplug the wire connector going to the solenoid, should I be able to read 12 volts from the 2 wires coming from the switch when activated? I want to rule out the switch before I look at removing the solenoids and cleaning them. The coils for the solenoids must be good or the hoist would never work. Any assistance or advice would be greatly appreciated. The truck runs great otherwise.

 

[Delmer]

Yes, you should get 12V at the solenoid connector. Then clean the solenoids, if that's possible.

 

[DMiller]

Man I detest working on old plow/salt trucks, the junker I use on the farm is the Brother In Laws on loan where it ALMOST has a cab left on it!! Always chasing lost grounds, eaten up solenoids or wiring just a mess. Keeps me busy just working on it to keep it running long enough to haul dirt on the place.

Check feed to and from the switch, could be a corroded connection dropping supply or delivery voltage just enough to not pull in the solenoid, then if possible disassemble the solenoid and clean it up as Delmer noted, then check the grounds are solid, solenoid, cab, whatever body panel the solenoid is connected to etc.

 

[Welder Dave]

The truck comes from Alberta where they don't use a lot of salt on the roads so it isn't rusted too bad. I'm thinking if I consistently get 12 volts going to the valve, the contacts for the solenoid are dirty. I thinks it's an easy first test and I can see if the voltage fluctuates at all too.