I received got a tb135 with hydraulic thumb. The thumb goes out without a problem but doesn't go back in with any regularity. Sometimes it does but 90% of the time it doesn't. I originally got it working by tapping on the joystick. Seems like when it does work it works until you shut the machine off. I'm thinking obviously it's in the joystick but haven't dove into taking it apart. Switch in the joystick bad? Yes. I already checked the one way valve.
Did you ever figure this out? I'm having the exact same problem. I soldered a new switch into the handle circuit board, but the problem still exists. I hope you figured it out and can share the solution. I have been hunting for the right/left service relay locations but cannot determine where the relays are located (maybe they are built directly into the solenoid valve?).
I did not get the thumb fixed just been dealing with it which makes building boulder walls & steps challenging/ time consuming my machine needs a month of shop maintenance
Usually its a bad wire from the switch down into the armrest. They're pretty small and work harden and then break inside the insulation so you cant see it. If its an aftermarket handle theres usually a spare wire or 2 in the harness so you can swap over without replacing the entire harness. Its pretty easy to test and confirm with a multimeter
Thanks! I'll definitely check that first. It's a factory handle, I believe. It's spotty (sometimes it works and sometimes it doesn't), but only the opening function. The closing action always works. Incidentally, do you know if there are actually separate relays for the aux service/thumb (or are they built onto the solenoid/valve circuit)? I found them on the electrical wiring diagram, but I cannot figure out where they are located in the machine itself (they don't seem to be noted in the compartment behind the fuse box in the left side "electrical" compartment with the other relays.
Back at this - I'm either going to attempt to replace the entire handle or replace the broken wire. Is there anything special I need to know about disassembling the armrest? It appears to have two Phillips screws in the front, and a torx or star bolt that secures the actual armrest. Do the wires terminate right there in the armrest somewhere? Looks like replacement handles have bullet connectors at the ends of the wires, and I just need to find where those go.