Testing a Neutral Safety Switch

Discussion in 'Electrical' started by undertakerman, Jul 13, 2020.

  1. undertakerman

    undertakerman Member

    As you gentlemen know I have had a problem getting my 65 Plymouth Sport Fury to start. I have 727 Automatic Transmission. There is a single wire running from the Starter Relay to the NS switch which I have continuity between the two points. I know that its function is to not allow power to the starter in any other gear other then Park or Neutral. I also know that when the ignition switch is moved from the RUN position from to the START position it sent's a signal to the NS switch and the Starter Relay connecting the BATTERY to the starter therefore engaging the starter starting the engine providing that the car is in PARK or NEUTRAL and if is not and in any other gear the car will not start. So my question is How do I test the Neutral Safety Switch to see If its working.
  2. 67Mopar

    67Mopar Moderator Staff Member

    The neutral safety switch acts as the ground for the circuit. Power runs from the Battery(+) to the ignition switch, out of the switch via the Start contact pin, then on to an electromagnetic coil in the starter relay, then through the neutral safety switch to ground, which of course is connected to the Battery (-) completing the circuit.
    If the neutral safety switch is no good, you have no ground, and therefore no circuit... the car will not start, you will not hear so much as a "Click" from the starter, nothing, dead.

    Testing the switch is easy enough.... ensure the vehicle is in Park or Neutral, Park preferred. Rock the chassis forward/backward to make certain that the vehicle transmission is actually in Park. Sounds silly I know, but it wouldn't be the first time I ran across a vehicle that wouldn't start simply because the transmission wasn't fully engaged in the Park position... it happens.
    Once you know you are locked in Park, just pull the wire off the switch (assuming it's one wire switch since it's for a 65)... then check for continuity between the pin on the switch, and the casing of the transmission. If you have continuity, your good, the switch is grounding the circuit as it should.
    67r/t4speeder likes this.

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