Common mistake: plugging the line to the pressure switch

Last Updated on by Brian A Cummings

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Common mistake plugging the line to the pressure switchIf you think of doing this, then you are committing a big mistake. If you do this, then your air compressor will no longer work properly. And believe me; you don’t want that to happen, because you will then spend unnecessary money to buy a new one.

Here is one important thing you should remember, there is nothing installed or connected to your air compressor that is not necessary. Therefore that line that comes from your tank, check valve near the pressure switch is there with a purpose. If you plug that line, then it will no longer work in the same way.

Some think that this is a good option because of a broken line, a solution that will no longer require an expensive replacement. But here are important notes why you shouldn’t do this:

The line

You might be wondering what this line is. This line is connected to the compressor into the base of the pressure switch. It could be a copper or aluminum line and can be distinguished by a red triangle. This line can be seen starting from the fitting to the air line where the compressor pump meets the tank. The large line faeeds from the compressor pump. If you check the fitting, it is connected to a brass plate at the bottom center and it usually contains either a one-way or a check valve. This line runs from that fitting to the pressure switch.

The function of the line

The line is important because it is connected to the fitting and the air passes from the pump into the tank due to that fitting. From the fitting the air passes through the smaller air line until it reaches the pressure switch.

This pressure switch contains an unloader valve. It can be part of it or mounted to the side. The line from the tank, check valve connects to the pressure switch and connects to the unloader valve.

This is how the air flows using that line. The compressor pump produces the air padding through the line going to the fitting. It then flows to the pressure switch passing through the smaller line. Remember that when the compressor is running the unloader valve is closed and cannot escape. Then it will go into the tank, and increases the tank pressure until it reaches the cut out pressure setting and stops the compressor.

When the compressor unloader valve opens

When the compressor stops to pump air due to the increase in air pressure that reaches the cut out pressure setting, the unloader valve opens. However, in cases where there is trapped air in the piston of the compressor pump, this adds to the load of the piston. There will be a difficulty for the compressor motor to start again after this added load.


Therefore, when you plug the line to the unloader valve, it will no longer start the compressor. This is because of the trapped air in the piston that prevents the cycle of pumping air to the pump. This will result on the compressor going to a thermal overload that can either result in a trip on the breaker or fuse blows. This will result to a much bigger problem even for the best portable air compressor that you have.

The best solution

Don’t let this problem put you down. There are cheaper options and better solutions that you can be found in your portable air compressor review notes. The common problem is that the cost of the OEM is expensive. But you don’t need to replace your OEM machine. All you need to do is go to an authorized compressed air fitting supplier; the common is the Google industrial air cylinders. Here you can check and buy the fittings that you will need to replace the hard metal with a new polyurethane tube. This tube instantly fits, which is why it is highly recommended (also known as “quick fits”). You will still spend, of course, but not very pricey. The range is $20-$30.

However, this solution only applies if you do not use your air compressors commercially. Thus, if commercially used, you will need to replace the OEM with an OEM metal tube. This is because the polyurethane tube cannot run for long periods of time.