Intermittent backhoe issue on my JCB any ideas?

[digdumpdrive1263]

I'm looking for some advice about my used JCB 3CX. It's been great but the backhoe has this weird problem.
It uses a rocker switch to start the hydraulics, which usually works. Now, it sometimes just stops. If I wait a bit (20 mins to an hour) it works again.
I've checked the fluids, changed the switch, and checked the wires. All looks good.Could a temp or pressure sensor be the problem when it gets hot? Or a bad solenoid?

Any ideas? Has this happened to anyone else with a JCB?

 

[dust-free_mojo]

I'm looking for some advice about my used JCB 3CX. It's been great but the backhoe has this weird problem.
It uses a rocker switch to start the hydraulics, which usually works. Now, it sometimes just stops. If I wait a bit (20 mins to an hour) it works again.
I've checked the fluids, changed the switch, and checked the wires. All looks good.Could a temp or pressure sensor be the problem when it gets hot? Or a bad solenoid?

Any ideas? Has this happened to anyone else with a JCB?

Could be heat-related, yeah. If the solenoid or hydraulic control valve is sticking once things warm up, that could explain the delay before it kicks back in. Have you tried checking voltage at the solenoid when it fails or feeling if it's hot to the touch?

 

[d0ugg.348]

It sounds like it's overheating and then kicking back in once it cools off so I'd also suspect the solenoid on the hydraulic pump. It can drop out when it gets hot and the coil resistance changes.. then when it's cool again, it makes contact and you're back in business like you described. Next I'd check would be the pressure relief valve. Sometimes they can get a bit sticky and not operate correctly under load, which would also explain the intermittent issue. Have a go at those two spots first!

 

[Teo_McDohl]

From what I dug up, relays and solenoids often go intermittent when they overheat... old contacts expand slightly and stop working until they cool. Swap your suspect relay with a fresh one or test it, and maybe monitor if it just quits when hot. Could be your golden ticket.

 

[yourguyharold]

I'm looking for some advice about my used JCB 3CX. It's been great but the backhoe has this weird problem.
It uses a rocker switch to start the hydraulics, which usually works. Now, it sometimes just stops. If I wait a bit (20 mins to an hour) it works again.
I've checked the fluids, changed the switch, and checked the wires. All looks good.Could a temp or pressure sensor be the problem when it gets hot? Or a bad solenoid?

Any ideas? Has this happened to anyone else with a JCB?

That's often a telltale sign of a solenoid or coil issue. It's a classic intermittent fault, and @d0ugg.348 explained it well.. I'd start by looking at the solenoid that controls the backhoe hydraulics. If you can, also check the resistance on the coil when it's cold and then again when it fails. @Teo_McDohl's suggestion is also a good troubleshooting step. Swapping the suspect solenoid with one from another part of the machine that's less critical will tell you if it's the solenoid itself or something else in the circuit.

 

[Guav444]

It sounds like it's overheating and then kicking back in once it cools off so I'd also suspect the solenoid on the hydraulic pump. It can drop out when it gets hot and the coil resistance changes.. then when it's cool again, it makes contact and you're back in business like you described. Next I'd check would be the pressure relief valve. Sometimes they can get a bit sticky and not operate correctly under load, which would also explain the intermittent issue. Have a go at those two spots first!

I think the solenoid is the top suspect. you're right that a solenoid has a copper coil, and over time, the insulation can break down. When the coil heats up, its resistance increases, and it can fail to pull the plunger. When it cools, it works again.

To test it, the next time it stops working, check for voltage at the solenoid's connector. If you have voltage but no action, the solenoid itself is bad. If you have no voltage, the problem is further upstream (like a relay).

 

[dig4ndtill]

You nailed the testing! Checking that connector voltage will tell you if the problem is the solenoid or somewhere else. Good call on how copper coils go bad, too. The insulation breaks down over time, especially with heat. You might even notice the click sounds different when it fails. If you want a quick check, try swapping in a working solenoid from something else.