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Cat 303E joystick voltage

Discussion in 'Compact Excavators' started by Skinned Digits, Jun 30, 2022.

  1. Skinned Digits

    Skinned Digits Member

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    Can anyone advise what the voltage should be going to the proportional roller switches on the joysticks?
    I have 12 volts (14 when running) going into LH & RH.
    Output voltage between the two control wires on LH is +2.5v * 0 * -2.5v

    The RH (hydraulic thumb) works in one direction only. Output on RH is +2.5v * 0 * 0v
    The switch is not available separately and is nearly $600 for new handle.
    I removed the rocker from switch an found the magnet disintegrated on one end.
    After reading some posts here about 3D printing a new rocker (hats off to Ryan Bunce), I thought that may be a fix.
    However, I switched the rocker (with a good magnet) from LH switch to the RH switch and the RH switch still only outputs in one direction.

    In searching online for a substitute switch, it seems most of them use a 5 volt input. Cyber-Tech advertises a 5 volt regulator for their switches. I am questioning whether the 12 volts on this machine is correct or if there is supposed to be a regulator upstream that has failed? CAT part number on wiring loom is 452-2983
     
  2. Nige

    Nige Senior Member

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    Need a Serial Number to look at the electrical schematic to get the voltage. If it’s like the skid-steer product line joysticks it will be a digital 8v supply produced from inside the ECM but by the sound of your measured 12v maybe not.
     
  3. Skinned Digits

    Skinned Digits Member

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    Was hoping you would see this. Cat 303E CR ser# 0303EEHHM01280
     
  4. Nige

    Nige Senior Member

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    The mini excavators are obviously different to the Compact Equipment line then........
    The joysticks use machine voltage as a supply. The power comes from the fuse marked "joysticks" in the fuse panel.
     
  5. Skinned Digits

    Skinned Digits Member

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    Thanks very much for your help on this.
     
  6. John C.

    John C. Senior Member

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    The serial number prefix does not come up in any of my info. I'm wondering if you have a gray market machine? FYI, Cat went to PWM joy stick switches on most of their models of excavators so it may be that yours don't regulate control by analog voltages. Minis might be different but it needs a deeper look.
     
  7. Nige

    Nige Senior Member

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    The Serial Number shows up on the system, so not a grey market machine AFAIK. My info came from UENR6678 which covers 303E machines with S/N HHM1-up.
    I must admit I was surprised but I don't think the schematic is going to lie.

    upload_2022-7-3_17-47-23.png
     
  8. John C.

    John C. Senior Member

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    Do you show a year of manufacture on the serial number? It would give me an indication of the accuracy of mine. My info only shows machines built in China and Japan for the North American market.

    I only bring up the type of switches as something to check. I've seen plenty of damage done by people probing couplers looking for analog signals and end up grounding out a digital input or output.
     
  9. Nige

    Nige Senior Member

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    DOM - 3rd June 2015.
    Attached a copy of the electrical schematic.
     

    Attached Files:

  10. John C.

    John C. Senior Member

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    Looked up the prefix without putting in a model and came up with the machine. That's a quirt in my source I didn't know could happen. Thanks

    The statement of a magnet in the switch is curious. The analog switches I'm familiar with just have a contact sliding over a coil. I don't see a controller in between the switch and the solenoid, so it must be an analog system.
     
  11. Nige

    Nige Senior Member

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    I think that the output of the joysticks must be PWM, because if you follow the wiring (take X782 in the illustration above as an example), it goes to the "PWM IN" side of what is labelled as a "power driver", the output of which goes directly to a solenoid.

    That makes sense when the OP said he disassembled the joystick "switch" and found a broken magnet inside it. A regular occurence on skid steer machines where the joystick thumbwheel switch has a PWM output. If only Cat would service the microswitches separately......

    upload_2022-7-4_12-11-18.png
    upload_2022-7-4_12-12-12.png
     
    mg2361 and John C. like this.
  12. Skinned Digits

    Skinned Digits Member

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    "If only Cat would service the microswitches separately....."
    If only - If I can't come up with an alternate switch, I will plumb a foot operated pilot valve to control this function.

    For any that might be following this - If you own machines that have the proportional electrical thumbwheel controls, and you have an open cab and work in a wet environment, consider covering the joysticks with a plastic bottle or something when the machine isn't being used? Cat uses a "Hall effect" switch with a sintered magnet. The magnet is not visible but is exposed to the weather. It looks like they might use a shellac to seal the magnet from moisture. Once water gets past the coating, the magnet will disintegrate. My machine has less than 900 hrs but it has spent a lot of time in the outdoors.
     
  13. John C.

    John C. Senior Member

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    Have you tried finding something similar from Digikey? https://www.digikey.com

    I have found microswitches, relays and resisters there with digits I got off the used components.
     
    digger doug likes this.
  14. Skinned Digits

    Skinned Digits Member

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    Yes, I have checked digikey and mouser. Found some that may be able to be retrofit but they usually want a 5 volt power supply. That's why I needed to know if the 12 volts I measured was correct. A company called Cyber-tech offers what they call a 5 volt regulator so that should remedy the voltage issue.
    Only numbers found are on stickers attached to harness. They seem to be Cat numbers - yet Cat does not offer the switch/harness separately?
     
    John C. likes this.
  15. Nige

    Nige Senior Member

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    That's what we found when trying to come up with a replacement thumbwheel for a skid-steer joystick. The power supply in that case was a digital 8v produced inside the machine ECM but all that was available from the most prominent companies manufacturing microswitches were switches that required a 5v supply.
     
  16. Skinned Digits

    Skinned Digits Member

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    I noticed that several of these switches seemed to be rated for a substantial over-voltage? Ruffy SAT specs show the max overvoltage is 20 volts? There may be some wiggle room on voltage?
     
  17. Nige

    Nige Senior Member

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