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SA 250 oil pressure sensor wiring

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  • SA 250 oil pressure sensor wiring

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Name:	16516304944956929718623269438467.jpg
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ID:	714735 I recently purchased a mid-80s model Sa 250 and I am doing some rewiring on it. I am confused on the wiring diagram for this model as to where the 2 wires go to from the oil pressure sensor. It looks like one of the wires goes to the temperature gauge. The other I don't know. I don't quite understand how this would wire in or shut anything down as it is a manual shutdown on this unit with the Perkins engine.

    ​​​​​ Would anyone have more insight as to where the second wire goes? The diagram only shows one wire coming off of the pressure sensor.
    ​​​​​​
    Last edited by AEmery; 05-03-2022, 09:16 PM.

  • #2
    As I recall they have the ign switch wired thru the gage so it wont start or run if there is no oil pressure. Its not wired to temp. But,,, this is from, memory so,,,,,,,,,,,,,,,,,,,,,,,,,,,
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    • #3
      Originally posted by Sberry View Post
      As I recall they have the ign switch wired thru the gage so it wont start or run if there is no oil pressure. ...
      Wouldn't there not be any oil pressure unless it's already running? Or are these mechanically different from typical automobile engines?

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      • #4
        I absolutely forgot these were diesel,,, ha,,, but,,, on SA the oil pressure sender is really low, 6 or 7 # and it comes up past that when cranking the starter.
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        • #5
          There is 2 wires to it,,, must be in series with something?
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          • #6
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ID:	714749 Yes, I am not sure. The machine is pretty basic, all mechanical with no ignition or electric solenoids on the injection pump.

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            • #7
              If image above is correct, one wire to a ground source and one wire to "S" terminal (I believe- letter is hard to read) of "Engine Protection Relay" for oil pressure switch..... Temp Gauge (sender) also seems to have connection to same "S' terminal on "Engine Protection Relay"....

              Being there is what appears new wiring on oil pressure switch, my first impression is the it may be incorrect .....

              Click image for larger version  Name:	Screenshot 2022-05-07 155442.jpg Views:	0 Size:	74.4 KB ID:	714754

              Last edited by Dale M.; 05-07-2022, 06:02 PM.
              "Fear The Government That Wants To Take Your Guns" - Thomas Jefferson..

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              • #8
                Originally posted by Dale M. View Post
                If image above is correct, one wire to a ground source and one wire to "S" terminal (I believe- letter is hard to read) of "Engine Protection Relay" for oil pressure switch..... Temp Gauge (sender) also seems to have connection to same "S' terminal on "Engine Protection Relay"....

                Being there is what appears new wiring on oil pressure switch, my first impression is the it may be incorrect .....

                Click image for larger version Name:	Screenshot 2022-05-07 155442.jpg Views:	0 Size:	74.4 KB ID:	714754
                Dale M.
                I would agree with you. What I see is one wire coming off of one terminal of the sender and going to the S terminal. While the other terminal looks as if it connects to the originally talked about terminal, while the ground would be the sending unit itself grounding out to the block.

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                • #9
                  Originally posted by AEmery View Post

                  Dale M.
                  I would agree with you. What I see is one wire coming off of one terminal of the sender and going to the S terminal. While the other terminal looks as if it connects to the originally talked about terminal, while the ground would be the sending unit itself grounding out to the block.
                  This where you need a volt-ohm meter and determine how the contact arrangement is for the switch....I may not have a internal ground through threads into block.... With out testing its hard to say.... What it amounts to is assume nothing....
                  "Fear The Government That Wants To Take Your Guns" - Thomas Jefferson..

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