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Bobcat AHC Issue 773G

Discussion in 'Skid Steers' started by DeereJohn, Jul 1, 2016.

  1. DeereJohn

    DeereJohn Active Member

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    I just got a Bobcat 773G, that I was told needed a actuator for the hand controls. The machine did not tilt, threw code 32-31. When I switch the actuator plugs, tilt works perfectly with the left joysitck. When I go to raise/lower with the right joystick, I get the same code.

    So then I thought the problem was the joysticks. I put the actuators back to their original connections. When I swap the plunger things on the joysticks, I get the same code for tilt (32-31) and my boom works correctly - so it does not follow the joysitcks.

    Has anybody encountered this before? Or have an idea of where to go from here? Bobcat is quite proud of these parts and I am a little hesitant to start throwing money at it without knowing whats wrong.

    I have found other threads with this code, they always seem to be resolved with the actuator replacement. I believe my actuators to be operating correctly.
     
  2. lantraxco

    lantraxco Senior Member

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    I don't know this machine, but isn't there more to the joystick than the "plunger thing"? Or did you mean you swapped out the whole base of the joystick?

    Also, have you double checked all the wiring and plugs going to the tilt actuator?
     
  3. DeereJohn

    DeereJohn Active Member

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    Hi Lantraxco,

    The plunger thing has three wires, and operates when the sticks are moved in or out. I am assuming I dont have to swap the compete joystick assemblies. The plunger mechanisms have the same part number for both sides and I am pretty sure they are the only thing needed to check these functions (boom and tilt).

    I should probably clarify here, only my tilt and boom are electric operated, the forwards and backwards are mechanical linkages.

    I have checked all of the electrical connections, sprayed them down with lectra clean and hooked them back up. I have not found any cut of chaffed wires.
     
  4. huckleberry

    huckleberry Member

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    check the wires at the plug. we have had several AHC machines with the same problem. and about half ,the wires were broken on the handle side of the plug. The wires didn't look bad but if you pull on them one by one you can see them stretch. they were broken where they go into the plug
     
  5. crewchief888

    crewchief888 Senior Member

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    hand control only? (AHC)
    selectable hand/foot (ACS)
    metal or plastic controller?

    :drinkup
     
  6. DeereJohn

    DeereJohn Active Member

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    I checked the continuity from the "plunger actuator" to the computer and it checked out, the wires looked like they were in good condition
     
  7. DeereJohn

    DeereJohn Active Member

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    Ahh They are AHC controls, sorry about that. It has the metal controller.

    Any chance there are electrical manuals for this thing? I feel like it shouldn't be this complicated. Now I am getting a "Tilt not in neutral" code, and my voltage out of the actuator is 1.72, exactly where it should be and same as the lift actuator...
     
  8. crewchief888

    crewchief888 Senior Member

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    do you have the square aluminum handle sensors, or the small plastic ones?
     
  9. DeereJohn

    DeereJohn Active Member

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    I am going to say the plastic ones, I can get the part number if that helps
     
  10. crewchief888

    crewchief888 Senior Member

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    check and see if the aluminum bonnet on the back of the tilt spool is tight, and that the retainer bolt that holds the centering spring in the back of the spool is tight.
    i would check the handle/harness connector for a loose wire or pin/socket thats not getting a good connection.

    if you have the aluminum handle sensors, bite the bullet and buy the updated kit from bobcat.
    if you have the plastic handle sensors, and are POSITIVE you dont have an actuator problem the problem is possibly in the AHC controller.
    it's a sealed unit.
    about all you can do is swap it out and see if the problem goes away.

    i really hate the early AHC systems, not much info as to diagnosing the system.

    :drinkup
     
  11. DeereJohn

    DeereJohn Active Member

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    Wanted to give an update incase anybody else runs into an issue like this

    So when the machine is started, with no codes present, and I hook my voltmeter into the acutator motor wires (+/-) at the harness from computer to actuator (harness is connected), I can see 11-12 volts one direction (when the handle is moved, causing the tilt down to occur) and zero volts the other direction (then throws code)

    So the computer is not triggering the actuator in one direction, the polarites should just be switched

    Now on the tilt handle input side, with everything connected and no codes, hooked the meter to in to the harness from the computer side, positive on the signal from the tilt controller. I see voltage swinging back and forth with the controller and it appears to be within spec (if it wasnt, I think that a different code any way).

    So I know the computer is getting signal both directions, outputting only one, causing a fault on the other as it does not see the potentiometer in the actuator move

    I think I am going to bite the bullet and replace the computer.
     
  12. crewchief888

    crewchief888 Senior Member

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    you should NOT be seeing 11-12 volts at the actuator.
    sounds like the AHC controller is the problem


    :drinkup
     
  13. BC873G

    BC873G Active Member

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    DeereJohn, I am experiencing something very similar. Did the controller replacement fix the issue?

    crewchief888, interesting that you note a loose bonnet on the back of the control valve. I went ahead and replaced the spool rod seals because I had oil leaking through to the actuators and when I went to remove the end caps (bonnet) the tilt cap was very loose.

    I have an 873G with metal controller.
     
  14. DeereJohn

    DeereJohn Active Member

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    BC873G,

    It did fix my issue.

    Can you describe what you have gone through for troubleshooting?
     
  15. BC873G

    BC873G Active Member

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    DeereJohn, thanks for the reply. BTW, my 873G is hand control only (AHC). Here are some of the things I have done:

    1. I tested the harness from the handles to the controller for continuity.
    2. Verified the signal from the handle sensors to the controller. The neutral voltage was 2.15V on mine. My service manual for the 873G doesn't show a reference voltage for neutral. Each handle output 2.15V at neutral. I saw that you mentioned 1.72V. Did you get that from the service manual for your 773?
    3. Removed both actuators and verified the ram would move when voltage was applied. The lift actuator had hyd oil in it so I have purchased a new one to replace it. The actuators were the original ones for the model.
    4. Replaced the spool rod seals and o-rings.

    I haven't completely tested the harness from AHC controller to the actuators. I tried to do some testing but was having trouble getting enough jumpers in the plugs to read voltages. Did you just pierce the wire to take your voltage readings? The motor voltage from the controller to the actuators was around 5.45V.

    I just about have it back together again so I will be able to find out soon if the problem still exists. If it does, then the next steps are figuring out if the controller is bad or some intermittent issue with the harnesses from the handles to the controller.

    My problem was if I moved the lift and tilt handles together at the same time I would get a 32-40 error (lift handled not calibrated). I could operate the lift and tilt separately without much of an issue except for an occasional beep. As side note, the manual says that if you have an ACS machine the 32-40 error is (lift handle/pedal not in neutral) or something close to that.

    Does anyone know if the handles themselves can be calibrated? It looks like the only way would be to position the pins that hold the handle sensor in different locations. Just not sure.

    Thanks.
     
  16. DeereJohn

    DeereJohn Active Member

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    1. That is good, others have seen wires break, mine were fine as well
    2. My 1.72v reading was from the potentiometer wire on the actuator. I believe this is the green wire. You should have a constant voltage for the pot, a ground for the pot, then the green signal wire from the pot. This runs on 5V. Someone above stated it was 12, that is incorrect.

    The other two wires are slightly larger, and supply 12V to the actuator (red and black). I opened the plugs on the actuator, stuck a probe into the two larger wires (red and black, for the motor control) and re connected the actuator to the controller. This enabled me to see the voltage the computer was supplying to actuators during movement. This should be 12V during movement.

    In my case, I could only get 12v in one direction, the computer would not do -12v for the reverse movement.

    All of my errors were actuator based. Have you swapped the joysticks to see if the error changes sides?

    On my g series machine, I have never been able "calibrate" it the way you may see in other posts (holding the handles together etc).
     
  17. BC873G

    BC873G Active Member

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    I don't think it is possible to calibrate the machines with the metal controllers using the recommended "hold handles inward, power-on, hit PTO button, and release". At least when I try it, I never heard the actuators cycling. From what I have been able to determine it is the plastic controllers with ACS that can be calibrated in that manner.

    I still didn't get how you read the voltages to determine if polarity was changing. Are you saying that you opened the plug between the actuator and the controller (5 wire plug) and then put your probles in and the closed your connector with the probes inside?

    I haven't swapped the handle sensors yet as a test. I did switch the plugs at the actuator and if I remember correctly the error code remained the same. I would occasionally get a 32-35 error though (tilt handle not calibrated) regardless if they were switched or not. Mostly it has been consistent with a 32-40 error. To me it seems like the issue with between the controller and handles. I only replaced the the lift actuator because my seals were bad and figured the actuator was short lived anyway. It was still working when I benched tested it.
     
  18. DeereJohn

    DeereJohn Active Member

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    I still didn't get how you read the voltages to determine if polarity was changing. Are you saying that you opened the plug between the actuator and the controller (5 wire plug) and then put your probles in and the closed your connector with the probes inside?

    That is correct. I was checking for voltage to the electric motor inside the actuator (larger red and black wires in the plug).

    That all makes sense. If the code switches with changing the handles you have found your problem, if it does not and all your continuities check out, it sounds like the computer.

    Hopefully its a joystick, the computer was not cheap.
     
  19. BC873G

    BC873G Active Member

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    DeereJohn, I got the spool rod seals replaced and the new actuator installed over the weekend. My voltage to checks for neutral coming from the actuator to the AHC controller were 1.74V so I think they are both within spec. I do have a new issue though when I did some initial testing. When moving the loader forward, and especially turning one direction or the other, I am getting some uncommanded quick/fast drops with the lift. They don't stop until I release the drive levers. I didn't have any issue like that before replacing the actuator and seals.

    Thanks,
    Steve
     
  20. BC873G

    BC873G Active Member

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    DeereJohn, just wanted to report back that my issue was resolved after finding a bad socket in the connector that goes from the lift handle sensor and the AHC controller. I made a video of the repair that will hopefully benefit someone else.

    Cheers!