Bobcat 863 c series auxiliary hydraulics

[Chadrobbins]

I have no auxiliary hydraulics on my machine. I hit the switch and no lights come on and nothing works. Any help would be greatly appreciated.

Thanks

 

[chevy43]

The mice have been chewing through my wires on my bobcat. You might look for any evidence of that.

Also mine has a button for High Flow, Variable, and regular and certain things don't work unless you push the right one.

 

[crewchief888]

1st off, check your fuses
seem to remember theres a seperate module for the aux control, i thinks its on the inner LH side of frame, tucked up near where the lever pivots are.
in the past, ive run across machines that someone has put in an aftermarket ign switch, and it's wired incorrectly/ everything works except the aux function

 

[gypsycatfish]

Chad was this a sudden problem? I have a 1998? 873 and I am assuming the hydraulics would be the same, but could be wrong. I do have a manual, but I have limited knowledge. I do know how to read, so I may be of some help. Do the rest of the hydraulics work?

 

[willie59]

in the past, ive run across machines that someone has put in an aftermarket ign switch, and it's wired incorrectly/ everything works except the aux function

Yep, I've seen that before. Seems I recall the C series used the Aux position of the ignition switch to power up a solenoid that dumps pressure from the auxiliary hydraulic circuit to assist making and breaking the coupler connections. On the Bobcat ignition switch, when the switch is in the Ign position the Aux terminal isn't powered up. On aftermarket switches that look identical the aux term is powered up when the switch is in the Ign position, prevents auxiliary hyd circuit from working.

 

[gypsycatfish]

I just noticed that your unit is a C series, my unit and manual is for an F 873. In the F series i think the only difference between the 863 and 873 is the turbo (could be wrong). I looked in my manual and there is an electric solenoid on the control valve. Since you are not getting any lights or any other indication I am guessing the problem is up line from the solenoid. You could hook up a jumper with a toggle switch with long wires (if you have to raise and lower the cab) and see if the auxiliary hydraulics work and then work your way back. I will see if I can find time to read up on the electrical side, maybe I can find some useful information in that area.

 

[willie59]

The coils on the auxiliary circuit solenoid valves are not 12V coils, they work on a lower voltage via pulse width modulation signal from the main controller, 12V will burn them up.

 

[gypsycatfish]

Thanks for pointing that out. I would have checked for correct voltage first ( you should always determine the proper voltage before the smoke test) but left it out of my post. I have not had time to research the electrical controls for my 873 which may or may not apply for the 863. Sometimes incomplete advice is worse than no advice, but forums are a group effort to attempt to help strangers in need.

 

[willie59]

Pulse Width Modulation (PWM) isn't common knowledge, and it's really not possible to troubleshoot by checking voltage. That's because PWM works by pulse bursts of full voltage, whatever that might be, 5V, 9V, whatever the system (computer) is designed for. It gives a solenoid a full burst of voltage, then off, then another full burst, then off. This is typically used on proportional valves, such as the aux valves on a Bobcat. The thing you cant see with a volt meter is the "width", that full on/off/on/off, is varied by the width of how long the full on back to off lasts. A short burst of full on will only open the valve slightly. Whereas a long burst of full on will open the valve fully. But in either case all you see on a volt meter is voltage because this all happens in milliseconds. The only way to check PWM is with an oscilloscope.

 

[gypsycatfish]

Thanks Willie59 for the explanation on pulse modulation. I woke up in the middle of the night and was thinking about asking you to post about it. It is more difficult to learn about electricity and electronics than mechanical. When smoke testing if high voltage, you and or the equipment can turn into a crispy critter, in low voltage, your component and your bank account can go up in flames. Although I was aware of PWM, I have only a basic understanding. Unlike the old days, you can’t just stick a screw driver across the terminals to test components. The important thing to remember is that always check for proper voltage first and be aware PWN exists on our equipment.

 

[willie59]

No problem, glad if any info I offer is helpful. Again, PWM is typically used for proportional valves as it provides smoother and more precise control than variable voltage. It's easy to actuate "bang" valves, put 12V on it and bang, full open. But for precise proportional, if you just applied 1V or 2V to get the valve to move just slightly, not enough voltage to make magnetic energy to make the spool react. With PWM, it's full volt, then off, full volt, then off, and the width of the full on determines how much it lifts the spool. Additionally, this on/off/on/off makes the spool sort of bounce, as in a rapid vibration, this helps keep the spool from sticking and provides smooth proportional operation through the full range.

 

[gypsycatfish]

i understand the basic principle, but have been wondering how long of a pulse at full 12 would it take to burn out the coil. I guess it all depends on the duty cycle at full 12v for a particular coil. You got me going on learning more about pwm controls. If it would last long enough for the valve to open and see fluid flow for a couple of seconds, it would be nice, but I guess there is no way of knowing without rolling the dice. I do not like to gamble.

 

[willie59]

Same here, I know the concept of how it works, but it's way above my education on how to make it work.

 

[gypsycatfish]

Most of the valves have a manual override. You take the acorn lock nut off and there will be a regular lock nut underneath, loosen and turn the screw in to full flow but be sure to count the turns so you can set it back to the original setting. The coil should pull off so check the stem for rust or crud that could be blocking the magnetic field that moves the plunger (unlikely the cause but worth checking while you are there). I did some research last night and found some people saying you can apply full voltage for a short time to test, but I want to find a person that has the credentials to back it up. I did find one guy that worked for a heavy equipment company that was explaining the controlling of the coils, but I was too tired to absorb it all. My gut feeling is that you can do a short go no go test on a coil without damage. To know if the pulse time is correct would take equipment that most of us do not have but the pulse is determined by the controller board. A simple feel for a click on the coil body would be one test. Of course there is always the chance the problem is a mechanical one in the valve body, but the click test may catch that some times. I am going to talk to some people that are smarter than me (may take a while since there are several million of them) and get back with more information. I do want to read up on the switches etc. to get back to where I think Chad’s problem is located. Chad, have gotten yours working?

 

[gypsycatfish]

I should have said some PWM valves have a manual override not most . I have not checked my JD 310E but I do not think that they do.

 

[crewchief888]

I should have said some PWM valves have a manual override not most . I have not checked my JD 310E but I do not think that they do.

bobcats do not