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IT28G Slow lowering hydraulics and cannot use joystick to lower mast

Discussion in 'Tool Carriers' started by Cadwell, Jun 13, 2022.

  1. Cadwell

    Cadwell Member

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    Hello, i have an 03 IT28G with forks installed. The main lift cylinders will not lower unless manually powered (with a battery) at the solenoid on the manifold that is at the base of the cylinders. you only need to activate the right side for it to work because the left will do nothing. I have swapped all components from one manifold to another and nothing has changed. When I activate the right side manually, it is slow to lower (guessing because the left side will not work). To sum up what is going on
    -slow lowering hydraulics on main lift cylinders
    -main cylinders only lower when right side solenoid is activated manually and joystick is going down
    -joystick will not activate solenoid
    -
     
  2. Nige

    Nige Senior Member

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    Please supply a Serial Number.
    Is the SERV CODE icon lit up on the Monitor Panel in the cab?
     
  3. Cadwell

    Cadwell Member

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    the serv code is not lit and serial # EFW00105
     
  4. Nige

    Nige Senior Member

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    I don't know if you are aware but this is an ex-military machine built specifically as a 10T forklift for the USAF. There is very little information about it in the system apart from the fact that it is based on the non-military DBT-prefix IT28G.

    Please post a photo of the solenoid on the manifold at the base of the cylinders that you mentioned, plus info of any Part numbers you can find on it. I think you could be speaking about the load control valvewhich is logical if the machine was only ever designed for lifting use and not as a loader.

    The solenoids on those two cylinders are powered from the Ride Control Relay (they are not powered from anywhere on the joystick) so checking that should be the first step.
     
    mg2361 likes this.
  5. Nige

    Nige Senior Member

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    Another thing. If you look on the electrical schematic I sent you will see that there is a blocking diode wired in parallel across those two solenoids on the locking valve as a flashback arrestor. It might be well worth checking that out to make sure it hasn’t popped.
     
  6. Cadwell

    Cadwell Member

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    Thank you for the schematic! You are correct about it being military and USAF and it is still in use surprisingly. I will check that part of the system and get back to you. I also attached a picture of what I believe is the flashback arrestor based on what you have said. If it is not the right part please let me know.
    1.jpg 2.jpg 3.jpg
     
  7. Nige

    Nige Senior Member

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    That’s the diode. It should be checked electrically just to make it hasn’t popped.

    Follow the wiring on the schematic back to the Ride Control relay and identify that on the machine. It’s one of four identical relays so for a test you could swap it with one on the others, or test it by applying voltage to the coil, your choice.
     
  8. Cadwell

    Cadwell Member

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    Sorry for the delay, had other vehicles that needed to get out. I found out that when i put the ride control relay in it looses all power going to it, but as soon as i take it out the power comes back. I believe that is not normal. Could this mean this it is the machine control because wire 571-CN333 goes directly to it (the machine control) and it looks like its the power wire
     
    Last edited: Jun 28, 2022
  9. Nige

    Nige Senior Member

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    Try putting a different relay in the Ride Control relay slot. If you remember there are four identical ones right next to one another. That would eliminate the possibility that a defective relay is causing the problem.
     
  10. Cadwell

    Cadwell Member

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    i tried a brand new relay and it had the same outcome. going to check if there is continuity/resistance in the 571 wire
     
  11. Nige

    Nige Senior Member

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    Yes. The Ride Control relay coil is fed from the key switch via 161-CN331 and 571-CN333 is effectively the ground for the coil. You could try testing 571 for continuity with the plug on the Control removed, or if you disconnect it at the relay end and put a temporary wire direct to machine frame ground and see if the relay pulls in.

    EDIT: Sorry, just read your post above again and your comment about power/ground. In the illustration below the 161-CN331 wire is coloured blue. That means it is a wire containing machine voltage when the key is in the ON position. If you trace 161-CN331 backwards it goes to the fuse box via 161-CN222.
    The fuse box bus bar is fed from the the main power relay via 112-PU when the key switch is turned on. The MPR in turn is energized from the key switch via 308-YL.
    See Page 4 Grid C-3 of the schematic and look at the table there showing what the different colours mean.
    The way I interpret the schematic is that the Machine Control creates a path to ground to energize the Ride Control relay coil.

    upload_2022-6-28_10-46-41.png
     
    Last edited: Jun 28, 2022
  12. Nige

    Nige Senior Member

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    Digressing just a bit. If the Machine Control does prove to be defective then a replacement 262-1408 control would be supplied blank and would require the correct software to be installed into it in order for it to function. This would be a dealer-only job.