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Turning motors over through Series Parallel switch without inotion switch


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Hey guys,

Got a real thinker here for you. We're trying to turn the motor over in a 1964 Mack B-61 through the series parallel switch, but without the ignition switch. We have all the batteries tied together with the series parallel switch and starter, but don't know which two terminals to cross in order to get the motor to turn over so we can build up some oil pressure for a prestart. There are three small terminals located on the rear of the switch (see pictures). We established that the one with the red wire is a ground leading to the frame, so we did that. Then that same terminal is connected to the bottom terminal with a jumper wire. We put a voltage meter on the them and read that each one has 12.5 volts when it's set up the way I just described. However, when the jumper wire is disconnected, only the terminal with the ground wire reads 12.5 volts and the others have 0. My question to you is what terminals must I cross in order to complete the circuit and turn the motor over.

Let me know,

CJ

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two things here 1st. the s.p. switch will only get you to 24v .2nd then you will have to jumper the starter solenoid to make the starter motor engage and crank. as for the s.p. sw. wiring a good auto parts store should be able to get you a diagram. or look on line! its been to long since I have played with one. but if I remember right one small term. is ground, one should have 12v. that should go to the dash. the other term. should shift the sw. to make 24v. it and the starter start term. I think go together

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I am doing the same thing as you.Go to my post labeled Need Help.I posted the diagram from the maker of the s.p. sw.You should be able to hook the batteries up to the starter direct to turn over the motor.

If I'm looking at the diagram correctly, would crossing the #6 and #7 terminals result in the motor turning?

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The SP switch you have is to be used with 24V starter that has no solenoid on it.But the SP switch you have has four big cable ter on it and the bottom two has two smaller terimals on it and that is the two to use to make contact.One needs a ground and the other goes to a 12V starter switch.But I have used the 24V starter with the solenoid on top of it with this SP switch but I don't think you will be able to find a schematic of it cause it was not made to use with it. The SP switch you have has the SP switch in it with a magnectic solenoid built into it.

glenn akers

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I am confused. Are you just trying to turn the motor over to build oil pressure and not starting the motor until you have oil pressure ?

Yes we don't want to start the motor dry. We want to have everything nice and lubricated before we attempt to start the motor and have it run.

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If you still have the 24 volt system just follow the wiring diagram from the starter button mention above in the wiki section. I think in most systems the ignition switch is in the charging system for now you do not need it. With out looking at the diagram I think all you need to do is pull the batteries in series to get 24 volts to the starter. This should mean power to both solenoids if the cables are correct.

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Yes we don't want to start the motor dry. We want to have everything nice and lubricated before we attempt to start the motor and have it run.

Don't want to overstate the obvious, but on a Mack the ignition switch has nothing to do with whether it will run or not. If you have an engine with any doubts as to the effectiveness of the fuel cutoff. i would disconnect the fuel line before cranking.

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