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2685-8 left drive motor speed sensor

Discussion in 'Skid Steers' started by Bill Hunt, Jul 2, 2022.

  1. Bill Hunt

    Bill Hunt Member

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    Can anyone tell me where the left drive motor speed sensor is located on a cat 259d???
     
  2. Nige

    Nige Senior Member

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    Right on the bottom of the drive motor. The wiring harnes connector should be easy enough to spot.

    upload_2022-7-3_10-59-31.png
     
  3. Bill Hunt

    Bill Hunt Member

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    Dear Nige thanks a bunch for your answer. I hate to sound so elementary but is there 2 drive motors and if so then where is this drive motor located. As you can tell I'm no diesel mechanic but i learn pretty fast. I'm just trying to get acclimated to this recently purchased machine i got. Once again thanks for all who will chime in and help me out on this one
     
  4. Chrisso

    Chrisso Well-Known Member

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    Hi Bill, yes two drive motors, one on each undercarriage. Both have speed sensors that need to read correctly.

    First thing first... raise the cab and check all plugs and wiring, especially those that branch off to both undercarriages under the cab.

    Next, get the machine up on blocks and remove the bolts/plates on your axles that stop your undercarriages falling off. If the bushes aren't seized you'll be able to slide the whole undercarriage out a few inches for better access. 2685-8 is "Unexpected Motor Speed Detection Control" on the LHS motor so start with the LHS.

    May need to remove a few hoses to get to the allen head bolt for the sensor, maybe not. Remove sensor, look for any metallic debris. If you cant find anything wipe it clean and swap sensor with the one on the RHS undercarriage.

    Three things could happen:
    1) Nothing, 2685-8 keeps reoccurring, problem is still in your LHS speed sensor wiring.
    2) Fault changes to 2687-8 which is "Unexpected Motor Speed Detection Control" for the RHS, which means the sensor is bad.
    3) Fault mysteriously goes away. Could've been tiny piece of metallic debris on the sensor from general wear, or could've been a bad connection somewhere in a plug.
     
    Last edited: Jul 3, 2022
  5. Nige

    Nige Senior Member

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    Does this help.?
    upload_2022-7-3_17-52-59.png
     
  6. Bill Hunt

    Bill Hunt Member

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  7. Bill Hunt

    Bill Hunt Member

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  8. Bill Hunt

    Bill Hunt Member

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    Chrisso 20220703_212901.jpg I was able to get the machine on blocks as instructed and surprisingly i saw what appears to be that plug. And it is just hanging. It appears to be attached to the drive motor but ithe other end is not attached to anything. I'll send a picture to see if this is definitely the sensor. Of course it is dirty but it's the best picture i could get. I may be able to clean the area a little better to get a better picture. My question is: what is the other end supposed to be attached to. I assumed it should be attached to a wire coming from the machine but i don't see one unless I'm overlooking it. I also have the cab up as you instructed. Is it possible to send me somewhat of a diagram of what that plug looks like or comes from? Thanks a bunch for your time and patience
     

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  9. Chrisso

    Chrisso Well-Known Member

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    That'll run alongside the hydraulic hoses and through the machine frame connecting under the cab. Easiest way for you I think is to look at the RHS.

    That connector (receptacle) and the bit it connects to (plug) are called deutsch connectors. Looking at those photos they will both need to be replaced before reconnecting.

    If you post your s/n and ask nicely Nige will probably send you a schematic.
     
  10. Bill Hunt

    Bill Hunt Member

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    I tried to look at the other side but i couldn't see it. I'll try to look again today at the RHS. And i will most definitely post my S=N and ask Nige to send a schematic. Information is helpful that you've provided thus far
     
  11. Nige

    Nige Senior Member

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    Another question. Is this a fault that has appeared suddenly or has it been there for a while now.?
    You haven't bought this machine recently with the fault present on it by any chance have you.?

    The reason I ask is that my first thought when you said the harness/sensor connector was hanging was that your photo would show torn wiring (possibly not unusual if a tree root or similar has been jammed in there). The fact is that it doesn't, it shows what appears to be an unplugged connector. Based on photo that the "other end" (aka the male half of the connector) should be around somewhere not too far away. Looking at the other side of the machine ought to give you the best clue.
    Again this comes back to Serial Number. There are 8 different models of 259D (also plus potentially different sub-models within that 8) and it would be of major benefit to know which one of them you have, not least to help in posting an illustration of what the wiring that connects from the machine chassis to the speed sensor ought to look like.
     
  12. Bill Hunt

    Bill Hunt Member

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    That is exactly what happened. I bought it a week ago with this issue already just trying to rectify it and the loud beeping. I just recovered my serial number. It is as follows: CAT0259DPFTL07252. I will try and see what the RHS looks and runs to
     
  13. Nige

    Nige Senior Member

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    A lot of head scratching could have been avoided if you'd volunteered that information in the first place...........

    Attached is the parts diagram of the platform wiring but I am not sure if it will help you much. You might be better served investigating the other side of the machine and see how that is connected. I'm wondering whether this machine has had wiring ripped of at some time before you bought it and the previous owner simply couldn't be bothered to fix it correctly. If that is in fact the case the $64k question is what state the wiring is in at whatever point it was damaged. It might not have been repaired because it can't be repaired if you get my drift.
     

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  14. Bill Hunt

    Bill Hunt Member

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    Yes that isa really good question. I hipe thats not the case. I'll start with replacing the speed sensor. However i was able to get the T40 allen screw out but couldn't manage to get the actual sspeed sensor out. Is there any magic to it? I assumed it would fall out once igot the screw out. I even tooka small hammer and tried to jar it a loose but to no avail. It looks like the original one but i still wouldn't think it would be this hard to come out.
     

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  15. Chrisso

    Chrisso Well-Known Member

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    Have you tried replacing the connectors and plugging it back in? Not sure why you're removing the sensor since you found the harness unplugged.
     
    BigWrench55 likes this.
  16. Bill Hunt

    Bill Hunt Member

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    Because i sent pictures of the sensor and a senior member suggested that by looking at the end of the sensor it may need replacing. However i blowed it out and cleaned it and was going to try and see if that did the trick. Problem is i can't seem to find the end that connects to the sensor. I'm referencing the end that comes from the tractor. I just looked under the machine and saw the end of the sensor unplugged but didn't see what to plug it to. I'll look again today if i get off work in time. But what I'm faced with is that i saw a dangling wire which happens to be the sensor. Can't see where it goes. ANY SUGGESTIONS???
     
  17. Nige

    Nige Senior Member

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    Only what was suggested before to look at the other side of the machine. The connections should be similar if not identical.
     
  18. Bill Hunt

    Bill Hunt Member

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    Ok I'll try that tomorrow. Its tough to see that sensor from the bottom for some odd reason
     
  19. Bill Hunt

    Bill Hunt Member

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    This is the only wire coming from the machine that i see dangling. It does however reach to the speed sensor on the machine but does not fit. I've sent photos and as you can see, the grey plug coming from the machine does say DEUTSCH as you suggested and the speed sensor that's bluish/green. They look like they should connect but the plugs dont match. My question is: is there possibly another piece that attaches to make these two fit? And also I've tried everything within my power to get to and view the other side but my view is highly obstricted by the hydraulic hoses and i can't see the RHS at all. Otherwise i would access it and use it for reference. So are these the two plugs that i need. Thanks again for all of your troubleshooting and expertise
     

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  20. Nige

    Nige Senior Member

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    Your first photo shows what appear to be the TWO halves of a 4-pin Deustch connector (see photo below) plugged together. If you look closely at it the end closest to where your photo was taken it should unpug from the other half by pressing the plastic lever shown arrowed on the LH half of the connector. This ought to leave a connector to which the one on your sensor (your 2nd photo) will plug straight into.
    upload_2022-7-11_13-34-9.png
    To confirm that it is the correct wiring you're looking at, please check the wire colours/numbers that come into the back side of the connector and that they correspond with the terminal pin numbers shown below. they should be P769 Yellow, P770 White, 834 Yellow, & 835 Purple.
    upload_2022-7-11_13-28-11.png