Air compressor wont shut off [Fixed!]

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In this post, we shall look at why your air compressor wont shut off and some of the best ways to fix the issue.

Read it to the end if you’re trying to fix an air compressor that won’t shut off (just keeps running and running).


Air compressor wont shut off – why it is happening and what to check

So your air compressor wont shut off when full?

Well, here are the potential causes and the solutions to try:


You could be looking at a faulty pressure switch

A common culprit is a defective air-off pressure switch (That switch is intended to shut the compressor down when it reaches the right pressure) so this is the first thing you should check.

The good thing is that the pressure switch is pretty cheap and easy-peasy to swap out too (you can buy a replacement pressure switch cheaply from Amazon).

Typically, you will see it once you take the cover off- the pressure switch is usually tied to the tank and is the part with some wires going into the motor.

Go to YouTube and search for videos about “how to replace pressure switch on air compressor” if you want some help when it comes to swapping out the pressure switch.

Quick Tip: Before you proceed to order a new pressure switch, try to dismantle your unit’s pressure switch and thoroughly clean out both the diaphram plus the tube that leads back to its tank (just to be sure it’s not blocked). It could save you precious time and money.


There’s likely a broken check valve

Also, the tank check valve might not be good and you could need to replace that.

Now, the check valve tends to become loose or worn down over time.

Once this happens, air may start to leak out hence your air compressor’s pump could begin to run constantly to atone for lost pressure…

What you do is open the check valve (it’s below the pressure switch)…

There could be something inside there that’s broken (for instance, a spring) thus making it malfunction.

Indeed, if the pressure switch isn’t shutting off (so it’s causing the check valve to release erroneously), you should replace them both.


The tank has a leak (possibly)

A leak in the tank can also keep an air compressor constantly running..

You see, if there’s a leak somewhere in the tank, your air compressor wont shut off because it only does so when the tank becomes full (and now it can’t become full due to the leak).

That being so, check the tank for any signs of a leak and repair it.

The bottom-line is: your truck air compressor wont shut off (it really doesn’t matter the model) if something is preventing it from reaching full pressure.


The intake valve might have malfunctioned

It might even be a bad intake valve that’s the cause of the problem.

You see, the intake valve (also called regulator valve because it functions as a regulator of the air that’s getting into the unit and getting compressed inside the air tank) is known to wear out quite fast.

And when it does, your air compressor will start acting up for the simple reason that the pump will be struggling to bring in air that’s enough to make (and keep) the tank properly pressurized.

This results in the pump not shutting off.

Keep in mind that intake valves are dirt cheap (check prices on Amazon) and are very straightforward to replace.


You are probably looking at a malfunctioning gauge

For some models, especially Dewalt air compressors, a common cause of the fault is a misbehaving gauge (on its air tank).

Now, when the gauge is not operating the right way- and this is mostly due to corrosion-  pressure is likely to be misread so your compressor will fail to kick off when the designated cut-out setting is reached.


Well, you might need to install a replacement air tank gauge.


Other likely causes

Don’t forget that there are a lot of gaskets (mechanical seals) in there that could have become loose or cracked leading to leaks so check for leaking gasket(s).

Unfortunately, they are not that easy to spot- doing a soap test should however help you spot any leakages (do it and see if it will reveal any leaking gaskets).

Also, there are a couple of other parts that time and again lead to the issue including the motor failing (the motor may itself be dead!). 

Besides, the performance of your air compressor may be hampered by dirt and grime that has accumulated inside gradually during normal use.

Consequently, the pump performance suffers and it may start to keep running.

Your first step here is replacing the air filters- and you should be doing that regularly to avoid problems.

The final thing you need to know is that your air compressor might be underpowered because you’re using an improper extension cord with it.

Our recommendation is to change to a strong enough extension cord (or to plug it in directly).

It’s worth mentioning that most manufacturers expressly discourage the use of extension cords with air compressors.


Final words

A faulty pressure switch, a check valve that has malfunctioned, and leaks are the most common causes of an air compressor failing to shut off.

Other things worth checking include the gauge and the intake valve.

Also, remember that even the motor could be having problems so check it as well.

Now, if the above doesn’t fix it, you might have to consider putting your air compressor up for sale on craiglist (or other second hand pages) and hope you will get someone to buy it- otherwise, you could end up losing a lot of cash.


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