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Thread: SA200 Murphy Gauges

  1. #1
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    SA200 Murphy Gauges

    I have a 1966 SA200 that I'm trying to wire 4 gauges to. I bought the 4 gauge kit from BW parts that contains the relay for shutting off the machine in low oil pressure / high temp scenario. This is also the oil pressure gauge with the little button you push. From what I've looked at, I'm assuming you have to click this before starting so it will read enough oil pressure to run?

    This machine was already upgraded to automatic idle down and electronic ignition before I bought it. I'm trying to use the wiring diagram for it but I'm not sure on some things.

    First of all is the ammeter. I'm pretty confident it is hooked up correctly, I have positive wire on gauge to alternator. There was a broken ammeter gauge under the doors that hooked up to a little assembly (pic. A) that goes to a brass fitting, I just ran the negative to that same spot as the old one.

    On the hour meter I'm not really sure, and was trying to go off stuff I found on the forum. I have the positive wire ran to the on position on the switch and the negative grounded to the frame.

    The engine temp gauge goes into a hole that has a plug in it somewhere on the engine, from looking things up I thought it would be on the side of the engine block but I only found a plug that looks like the right size on the top (pic. B) is this correct for the sensor to go in?

    On the oil pressure line, do I just run that hose to this connection that already existed under the doors? (Pic. C)

    How do you change the set points on the gauges for when they cut the engine off?


    Lastly, wiring the relay. I have the wiring diagram that BW parts provides online as pic. D. I have the wiring from oil pressure gauge and temp gauge wired together and connected to 85 on relay. I have 87 on relay taped off and not using it. I have 30 on relay going to positive side of ignition coil. I have 87a and 86 on relay wired together but I'm not sure where it goes. It says ignition switch but where does it need to be with having the auto idle and everything? Pic. E shows the ignition switch wiring, right below it is starter button wiring and to the left of that is idle switch.



    I'm not sure on any of this at this point. Is any of this right? This is my first SA200 and my first time trying to wire anything like this.

  2. #2
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    Re: SA200 Murphy Gauges

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  3. #3
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    Re: SA200 Murphy Gauges

    might try do a search for similar title/keywords, someone in last couple months, had a similar murphy switches thread , and member 12v71 posts helped him out on it

  4. #4
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    Re: SA200 Murphy Gauges

    Alright, an update. My ammeter is working correctly, and I did some more research and saw the other plug for the coolant that im suppose to use on the side. The dirt on the engine kind of concealed it. Tried to get it out with a socket wrench with a cheater and ended up rounding off the hex inside the bolt. Filled it up with weld and welded a 3/4" nut on and it came right off. So that's hooked up now.

    I looked up that post by 12v71 and its helpful but my issue is, what exactly is meant by ignition switch? If you look at my last picture in the 2nd post you will see the wiring to the start button, then above it is the wiring to the on/off switch then to the left is the wiring to the high idle / auto switch.

    I'm assuming the on/off switch is the ignition switch. As you can see, one wire goes from the on/off switch to the idle switch. The other wire goes to the oil pressure switch shown in the first picture. Would I just go on the same screw as one of these? Does one of them come off and the relay wire go in instead? This is where most of my confusion is coming from.

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    Last edited by Leviwc; 11-15-2021 at 11:47 AM.

  5. #5
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    Re: SA200 Murphy Gauges

    [QUOTE=Leviwc;8835316]Alright, an update. My ammeter is working correctly, and I did some more research and saw the other plug for the coolant that im suppose to use on the side. The dirt on the engine kind of concealed it. Tried to get it out with a socket wrench with a cheater and ended up rounding off the hex inside the bolt. Filled it up with weld and welded a 3/4" nut on and it came right off. So that's hooked up now.

    I looked up that post by 12v71 and its helpful but my issue is, what exactly is meant by ignition switch? If you look at my last picture in the 2nd post you will see the wiring to the start button, then above it is the wiring to the on/off switch then to the left is the wiring to the high idle / auto switch.

    I'm assuming the on/off switch is the ignition switch. As you can see, one wire goes from the on/off switch to the idle switch. The other wire goes to the oil pressure switch shown in the first picture. Would I just go on the same screw as one of these? Does one of them come off and the relay wire go in instead? This is where most of my confusion is coming from. [quote]


    I'm trying to figure out the best way to do this, since I have no idea how the "updates" were installed or wired, you basically want to use the relay to interrupt the circuit to the ignition coil. Yes, the on/off switch is the ignition switch and that's where the power to 86 and 87A should come from and 30 goes to the coil.
    So, the wire from ignition switched power to the coil will be the one you cut to go to to and from the relay. It would be really good if the guy that did the updates could supply a schematic for his wiring. Some things don't look exactly right to me, but I'm not a total expert on the Idler and electronic ignition.

    Oops, yes the push button on the oil pressure gauge is the start up bypass, and to set the desired limits on the gauges there is a small "screw" looking thing on the face to turn the stationary contact. Usually with a small allen wrench. some of the older ones had a screwdriver slot.
    Last edited by 12V71; 11-15-2021 at 08:53 PM.

  6. #6
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    Re: SA200 Murphy Gauges

    @Leviwc

    I hope you have better luck that that braided hose then I did from BWParts. I have a leak between the ferrule and the brass nut connecting to the pressure gauge and when I tried to start the machine it had coolant spraying from it. Have an email to BW Parts about how I can fix it without having to drain the coolant and install a compression fitting to a different hose, I saw that duaneb55 installed a plastic hose on his and put heat resistant wire loom around it and that might be my only alternative. Needless to say I am in the same boat with you in learning how to rebuild an SA200 but I do enjoy it

  7. #7
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    Re: SA200 Murphy Gauges

    Quote Originally Posted by pipewelder View Post
    @Leviwc

    I hope you have better luck that that braided hose then I did from BWParts. I have a leak between the ferrule and the brass nut connecting to the pressure gauge and when I tried to start the machine it had coolant spraying from it. Have an email to BW Parts about how I can fix it without having to drain the coolant and install a compression fitting to a different hose, I saw that duaneb55 installed a plastic hose on his and put heat resistant wire loom around it and that might be my only alternative. Needless to say I am in the same boat with you in learning how to rebuild an SA200 but I do enjoy it
    You're getting coolant spray from a pressure gauge connection??? Huh?? What have you mis-connected?

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