How to Check an Automotive Neutral Safety Switch

Your neutral safety switch is equipped on every automatic transmission made, and keeps the starter control circuit open when the shifter is in a neutral position. If you notice that your car or truck is not sitting in neutral, will not shift into neutral, or is stuck in neutral, this could be a problem to look at before you pay for a new transmission.

To begin, you should always have your wheels chocked, and allow time for your car to cool completely. Now place your shifter into the park position so the car or truck does not move, and turn your key over to the start position. If your starter works properly, then the park position on your column will work right. Now that you know that park is correct, move the shifter to the neutral position until the lever at the end drops off the neutral stop in the selector window of your dash. If your starter works again when you start the vehicle, then your linkage in the gear shifter is aligned and properly adjusted now. This small test will test not only your neutral safety switch, but it will also help you to check the adjustment of the switch; which is crucial to its operation. If you find that your car does not turn over when you place your gear selector in either position noted, then the neutral safety switch is not working right, or the gear selecting linkage should be fixed or replaced.

So you knocked out two birds with one stone with this test.

Now manual vehicles use a clutch start switch to connect to the start circuit. What this does, is it keeps your vehicle from starting unless the clutch pedal is completely pressed down to the floor. Your switch is almost always open when the clutch pedal is released from the floor. So when it is pressed down, the switch will close and your circuit between the ignition switch and starter solenoid is complete. You should check this if your vehicle does not want to start, after you have checked the battery and electrical system for errors. Since your clutch pedal is wired between the ignition switch and the starter relay coil, your engine won't try to start if the switch is bad. Depending on the type of vehicle you have, some clutch start switches are located on the clutch pedal assembly, and then others will be on the master cylinder push rod.

To check this switch, disconnect it at the clutch pedal assembly via the connector. You can use an ohmmeter to check for electrical continuity between the two terminals when the clutch is engaged and released. If your clutch is released and not pressed to the floor, there will be absolutely no action at all on your ohmmeter, meaning there is no continuity. With your clutch pedal pushed to the floor, you should have that ohmmeter going haywire with activity. If your switch doesn't finish the circuit while the clutch is pressed, check the adjustment of the switch. If it is correct, just put the switch back on. If you do not have an ohmmeter, the MacGyver way of doing this is to just use a piece of wire bare on two ends. Bypass your switch with the wire, and if your car starts, then you have a bad switch.