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How Does it Work
/ Neutral
Safety Switch
How a Neutral Safety Switch Works
An important car electrical
component is the neutral safety switch. This switch disables the
starter operation when the vehicles transmission is
not in neutral or park. If the engine was allowed to
start in gear the car would immediately begin to move once the
engine started. Neutral safety switches are equipped
on automatic transmission vehicles only. On most
vehicles the reverse light function is integrated into the neutral safety
switch. The location of the switch can vary; designs can include a transmission
selector shaft or steering column mounting location. A neutral safety switch
carries starter solenoid voltage when the ignition key is turned to the start
position. This switch works the same way a normal switch would work except the
neutral safety switch is controlled when the vehicle gear selector is moved
throughout its range from park to 1st or low gear. When a neutral safety switch
fails the starter or reverse lights will not operate.
Neutral Safety Switch (appearance will vary)
Testing Neutral Safety Switch
Required Tools:
Test Procedure
- Locate the neutral safety switch
- Disconnect the
wiring connector at the switch
- Using a test light or volt-meter test for power at the wiring harness with
the key in the "engine crank" or the gear shifter in the "reverse" position.
(do not start the engine)
- If power exists reconnect the neutral safety switch and probe outgoing wires
at the connector.
- If no outgoing power is present the switch has failed and needs to be replaced.
Tip : If the engine will not crank over with the car in "park"
push down the brake pedal and try cranking the engine over with the car in "neutral".
What you are doing is bypassing the "park" position in the switch and now are using
the little used neutral circuit. If in neutral the engine starts the switch is probably
bad.
Tip: Sometimes a neutral safety switch can become misadjusted.
This switch adjustment can change due to normal wear of mechanism that controls
switch slider.
Other complications can occur if there is a loose connection somewhere in the
system. While this condition is not a shorted circuit problem, it is a condition
that simply breaks the flow of electricity intermittently. To troubleshoot this
problem consult a car repair manual to locate the wiring schematic for your car.
Repair the broken or shorted connection as needed and recheck system. Electrical
problems are less complicated when the proper information is available. If
technical assistance is needed, ask our team of certified technicians.
How Does it Work
/ Electrical
WARNING! Always have the vehicle under inspection on level
ground, in park with the emergency brake on. Always wear protective eyewear, gloves
and necessary clothing before inspection or work begins. Never crank an engine over
when anyone is near the battery or engine. Always have an operational fire extinguisher
close by, obey all first aid instructions in the event of an accident. Never stand
in front or behind a vehicle when cranked over or running. When engine is cranked
over keep hands and clothing free from rotating components.
Troubleshooting
/ Neutral
Safety Switch
Additional Resources
Check Manufacturer Specific Neutral
Safety Switch Questions and Answers
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