Cat 259D Aux Hydraulic Problem

[Dieselfixer]

Hi all,
I'm having a problem with my 259D. I have a clam bucket on it and when I open the bucket it quickly drifts back to the closed position. The cylinders on the bucket have both been rebuilt. I tried the bucket on a Bobcat machine and the bucket stays open. Any help is appreciated.

 

[Mobilewrench]

Most likely a problem with the switch on the joystick. Is your auxiliary switch a thumbwheel?

 

[Dieselfixer]

Yes, a thumbwheel

 

[Mobilewrench]

I know there is a way to use the on board diagnostics to read what the ecu sees for that joystick on the x y axis. I am not sure if it can read the rare earth magnet thumb wheel. You can test it with a multimeter that has a duty cycle function. If you can pin out the wires for the thumbwheel.
But, to be honest, anytime I come across a cat with a UFO or WTF problem on a system that involves that particular switch; the answer is replace the joystick.
I have never found a source for just the thumb wheel.
I had to replace that joystick in the same machine last year and I sort of remember it was a little pricey.

 

[Nige]

The joystick (handle along with all the buttons & thumbwheel) is sold separately to the base which has the pilot control valves in it. The base retails at about $750 IIRC.

If you want a Part Number for the handle you’ll need to post a machine Serial Number. There are a number of different handles depending on how the machine is equipped.

 

[Dieselfixer]

Thanks all. The serial number is FTL00436

 

[heymccall]

Before tossing the switch in, physically swap the quick connects on the bucket's hoses, so that the operation is reversed. Does it still drift shut?

 

[Mobilewrench]

Heymccall, are you thinking its a problem in the valve body? Because the bucket didn't drift on his bobcat so it isn't bypassing the piston seals in the cylinders.
Just asking because I have never had that a problem in the auxiliary valve on a cat skid before. Not saying it doesn't happen. But if you tell me you have seen it I want to keep it in mind so I don't blindly change a joystick in the future.

 

[heymccall]

Just reverse the quick couplings and try. Your results will help determine where to go next. It's not labor intensive to try, is it?

 

[Dieselfixer]

Reversed the hoses, now it will stay open but won't stay closed.

 

[heymccall]

Well, you've definitely ruled out a fault in the attachment.
The thumbwheel may be defective or out of calibration. Or, the the relief valve on that circuit is compromised. There could be debris in the relief valve seat, or it could be just plain worn out.

The fact that it closes quickly suggests thumbwheel calibration or damaged thumbwheel switch. I think there is a thread on here showing the magnets swelling or such at the thumbwheel.