The Neutral Safety Switch | Failure Symptoms, Testing, Cost & Replacement
What is a Neutral Safety Switch?
One of the very first lessons taught in any driving class is to never start or stop the engine in any other gear other than park or neutral. Doing so could have serious consequences, such as your car rolling into traffic. This is dangerous not just for you but for anyone that might be in the surrounding area.
To prevent something like this from happening to you, the transmission is equipped with what is known as a neutral safety switch (When shopping for a transmission you may also see it abbreviated as NSS). Also known as an inhibitor switch, this device is responsible for making sure your car is only able to turn over when the transmission gear is only set to Park or Neutral. Any other gear and the engine will not crank.
The origin of the neutral safety switch, as well as other safety features for most vehicles, can be traced back to the early 1960s with the formation of the Specialty Equipment Manufacturers Association, or SEMA as they are more commonly known.
While some features designed to keep drivers safe had been introduced in earlier years, SEMA helped bring these products into the spotlight and began the process of streamlining them, making them key aspects of any vehicle.
The location of the switch depends on the model of the vehicle, namely the type of drive the car is, whether being front wheel or rear wheel drive. The most common spot to find the switch is on the left side of the transmission, around the linkage that allows the transmission to perform its main job in switching between different gears.
4 Symptoms of Failure
It is important to know when the neutral safety switch may be going through trouble. There are different symptoms that you might be feeling if the switch is damaged or otherwise in need of replacement.
Engine Unable to Crank in Park or Neutral
One of these is if the engine is unable to crank when the transmission is set to Park but is able when set to Neutral. If this is happening, then the problem might be in the neutral safety switch or potentially with the shifter cable itself, being loose or adjusted poorly or even the cable being damaged.
On the other side of things, if the car is able to start in Park, but not Neutral, then the issue could be the switch suffering from an electrical failure. While the case is likely the safety switch, it is always important to make sure that everything else in the vehicle is running safely to make sure there are no other underlying issues that might have gone unnoticed.
Engine Cranking In Gear
A third issue that could potentially occur is if the vehicle is able to start in any gear besides just Park and Neutral. As mentioned before, this is a serious safety issue. Say you are starting your car and it happens to be in 1st or 2nd gear. Instead of just sitting there upon the engine cranking, the vehicle would lurch forward, possibly hitting another car, your garage, even the main road full of busy drivers.
This could happen if moisture in the neutral safety switch causes contacts to cross or there is debris causing physical damage to the switch. If this happens, then the power side of the NSS will short out, which is what causes the vehicle to start in gear.
If you notice anything wrong with how your vehicle starts, it is best to have it looked at as soon as possible, as letting it slide by could have serious repercussions for not just you but for anyone else around that might get caught up as well. It is better to be safe than sorry in this case.
Engine Unable to Start
In addition to affecting certain gears of the transmission, a bad neutral safety switch can also prevent the car from turning over entirely, no matter what gear it is set to. If this is the case and the engine will not crank in either Park or Neutral, then there is likely an electrical issue at hand.
The neutral safety switch is often connected to the starter relay of the engine, meaning if a part is bad there, then the whole system will be affected. With the electrical issues presented, there would likely be no power flowing from the switch to the starter, thus the engine not cranking. Without this, the engine will not have the ability to come to life.
If this is the case, then there might be an open electrical circuit in the switch, potentially due to a handful of causes, including a faulty relay, a blown fuse, or internal issues with the switch itself. If this is the problem you are dealing with, then it would be recommended to have your safety switch replaced as soon as possible. Replacement and repair costs of the part depend on the make and model of your vehicle, but having the piece functioning is vitally important.
Reverse Lights Not Shining
One lesser known fact about the function of the neutral safety switch is that it works with the reverse lights on many different vehicle models. If the engine is not cranking as well as these lights not coming on, then the switch could be at fault.
Having these lights on is not necessarily important while on the road, but there are still times when they are needed, so any pedestrians or nearby vehicles are aware that you are reversing and don’t cause an accident while you are backing up.
The neutral safety switch has a number of roles, and any one of them could possibly be affected by damage, so it is important to always be aware of its condition.
Having the neutral safety switch replaced can cost anywhere between $100 and up to around $350 for both parts and labor, depending on the make and model of your vehicle, as well as the type of specialist working on the system.
However, this cost can be skewed for more unique vehicles, such as newer models or foreign imports, as the build will be of a different design and there will be parts that might be added or omitted. If you are an expert wanting to do this job yourself, the safety switch costs generally between $30 and $60, though as mentioned earlier this cost can vary depending on your specific vehicle.
Neutral Safety Switch Replacement
Having a new neutral safety switch removed and replaced is a relatively simple process. After the vehicle is raised on stands to allow for accessing the transmission, the shift lever and the cable responsible for changing gears are removed, as well as the electrical connector from the switch itself. From there, the switch will be able to be removed from the transmission.
As mentioned above, the location of the switch varies depending on the model of the vehicle as well as the transmission style. On a rear wheel drive vehicle, the switch will be found on the driver side of the transmission (the left) and on a front wheel drive it will be on the top of the transaxle. In the case of the latter, it can generally be accessed from the engine compartment, meaning that the vehicle will not have to be lifted.
Once the neutral safety switch is removed, the unit will be checked for any signs of leaks on the shaft seal to prevent any further issues from occurring with the part. With the old piece removed, the new safety switch will be installed onto the selector shaft and then secured while everything is being aligned. With the switch locked in, the cable and shifter are reinstalled and the vehicle is tested to make sure the switch is able to handle its job before the vehicle is lowered.
DIY NSS Replacement
If you consider yourself a transmission expert and decide to handle this task yourself to save time and money, there are a few guidelines that should be followed. The first is the matter of lifting your vehicle.
It is important to have both a car jack as well as jack stands, especially if you will be under your vehicle. NEVER work underneath a raised vehicle while only using a jack. Have the stands installed in addition to provide yourself with the best possible safety while the car is raised. To make sure the vehicle is stable, with the vehicle on the jack stands give it a small push on the front corner. If there is any movement, no matter how little then the stands will need to be reset.
Tools & Supplies Needed
- Replacement NSS
- Car Jack & Stands
- 10mm wrench/socket with rachet
- 12mm wrench/socket with rachet
- Flat Head Screwdriver
The first step in replacing the NSS (Neutral Safety Switch) on your own is to disconnect the negative cable of the car battery, making sure that it is far enough back to not make contact while you are working on the switch as to not cause any electrical issues.
Depending on the type of vehicle drive, locate the switch. It is important to know that some of these switches have a plastic cover that will be coating the body of the switch. The switch will be mounted to its respective location by 2 or 3 bolts with sizes ranging from 10 or 12mm.
Also present will be the shifter cable or linkage with an electrical connector, which needs to be unplugged. Ensure that this hasn’t become too brittle and that it does not break when trying to unplug it.
Next would be removing the shifter cable from the pin that is going through the switch. This cable is generally held in place with a 12mm nut or bolt, so use the according tool. The final step in removing the old neutral safety switch would be the two 10mm bolts holding it onto the transmission.
Make sure you have taken note of the original position of the old safety switch so you will be able to install the new piece in the same way as the one being replaced. After removing those and the old piece, the new switch is ready to be installed. To do so, just follow the process in reverse and the new switch will be ready to roll.
Testing The Neutral Safety Switch
In order to test to see the quality of the neutral safety switch, there is a simple test that involves the wiring of the system and a voltmeter. The wiring will vary depending on the model of your car but a diagram should be found in your service manual that will show you all the connections. If you cannot find the diagram or the manual is not available, then an image should be able to be located online just by searching your type of vehicle.
Tools & Supplies Needed
- Voltmeter or test light
- Wiring Diagram (Found in service manual)
- NSS location (component location)
The neutral safety switch itself will have wires going from it to the starter solenoid, indicating their mutual relationship. When the transmission is in gear, meaning not in park or neutral, the switch is open and prevents any electrical current from running to the starter.
When the ignition is run, as long as the gear is in park or neutral then the current will be able to run up the wiring to the starter, allowing the engine to crank and the car to start. The aforementioned test is about making sure the connections on the wiring is solid.
To perform the test, attach a voltmeter to the wire that connects the neutral safety switch to the starter solenoid. This will show the amount of voltage running between the wires upon each test. The first test is to turn the ignition with the shifter set in the park position. If the engine cranks, then the corresponding position on the switch is correct. The same would then be done for the neutral position.
When doing each of these, the voltmeter should be reading the power present in the wires that is running from the switch to the starter. If there is no reading for either, then the switch or the wire could be suffering from damage or misalignment.
If this is the case, test the wires at other points for connections to determine the source of the issue. However, if the engine cranks at both these positions, then the switch and the linkage are running fine.
Quick NSS Test
In order to check to see if your neutral safety switch might be going bad, there is a simple do it yourself test to see how it is faring. With your vehicle in Park or Neutral, go and start the engine while softly giving your shifter a small wiggle to the point that it almost switches between gears. Doing this will engage a certain contact point within the switch, letting power flow through the starter relay.
If the vehicle is only able to start when you are doing this trick, then the safety switch will likely need replacing. This is due to the shift in the contact that is not meant to occur. While replacing the switch is a relatively easy job for those that are experienced with repairs, if you are not knowledgeable, it is best to seek help from a specialist.
While it’s not the largest piece of the unit, the neutral safety switch is still just as important as anything else, because just like any great team, the components of the drivetrain all work together to help you down the track or to the soccer field!
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