I recently got a tree shear for my older Bobcat 753. It is the only attachment that needs aux front hydraulics. Unfortunately the switches on the right hand steering lever that control front aux hydraulics are falling apart and only occasionally work. I started to dig into how to fix and looked up the control with switches and wires replacement part. The part is about $500.00 there are 2 switches, one for extend/retract and the other to switch to constant. OK, so I am looking at how to get it working without buying the part. I noticed that the left hand control seems to have the identical switches for rear aux hydraulics which this machine does not have. I was considering removing the left hand assembly and swapping it for the right. Then I noticed that the wires looked like they could be switched in the belly without having to cut or fish them thru the tube. Both sides have the same connectors, the wire colors are similar, the parts diagram seems to show only one part # so I think it will work to just switch the connections and having the left hand assembly control the front hydraulics. Too late tonight to try it out, but does this seem likely to work? Thanks for any input, I'll post when I try it out.
How did that work out
did not work because the left hand switch is also shot. It works by probing the hole that the left hand switch fell out of when I was working it. If the left hand extend/retract had not disassembled itself I would be shearing now. I guess step one of this scheme would be to ensure the left control is good, in addition to being the same.
You're going to have a problem rigging up a switch to control the front aux hydraulics. On the right lever, the thumb switch that controls the front aux hydraulics is a "Hall Effect" switch, it's not an analog on-off-on switch. That's how you get proportional control of the auxiliary hydraulics on those machines. An on-off-on type switch won't work because the main controller can only process input from a Hall effect switch on that circuit. The other switches, like for the rear aux option, are not proportional circuits so they will work with analog on-off-on switches.
This must be a really old unit. It has regular switches inside the control, not too user serviceable, but I couldn't give up. The aux hydraulics on this machine seem to be on/off only? After the switch didn't work, I found that it was separating from the control, so I removed the remaining part of the rocker. When I did, I found 2 small Philips screws under it, removed them and separated the halves. The broken extend/retract switch had 3 wires to it, I found a double throw momentary switch that fit inside the handle, , enlarged the hole thru the handle slightly for the new switch stem, spliced the switch to the existing wires, mounted it thru the old switch bezel, reassembled and it works great. I took photos of the operation, but cannot post here yet. Now on to my next project, figuring out how to utilize the tree shear rotation cylinder. It looks like it needs voltage to switch from the shear cylinder to the rotate cylinder, but that's for another post. Maybe replace the right hand switch with another like I did on the left.
I recall the old 743B was like that, had to push the right drive lever to the right to engage the auxiliary spool and use switch on the right knob for two way flow. I didn't recall the 753 was like that, must be an old 753 C series, of course I haven't worked on one of those in at least 15 years
Have been scowering the interweb for info on my 1994 753L Bobcat. Dont mean to high jack this post but seemed the most relevant. Just signed up here, alot of great info and insight. Willie obviously knows his stuff. I am mechanically inclined ( marine tech, mercruiser) The left boom pedal is sticky, cannot feather it. Checked all the linkage, looks good, the rod/valve appears to be the culprit. I have found info saying there is 2 check balls and a spring and wondering if anyones experience would tell them in this scenario I should be pulling the spool and checking balls and spring? If the balls and spring are there, Is it a thing where the balls can dig a groove over time that dont allow a smooth transition from up to down? A little leery about pulling apart, if I pull the valve rod out will the oil keep on flowing? Tips on plugging to stop oil flow? Thanks in advance for any insight.