Central Pneumatic Air Compressor Not Building Pressure Why? Let’s Resolve this Issue

You have Harbor Freight’s central pneumatic air compressor that is running fine but not building pressure, or suddenly the pressure drops. Is it? So, what to do? How can you troubleshoot this issue? Is there any need to call a technician, or can you do it yourself? All of these queries will be answered in this article today.

If you don’t have much knowledge about different parts of air compressors, you can hire a technician who will save your money and time. Also, you can seek help from Harbor Freight’s customer support. When the inquiry starts, you have to give the model number of your air compressor. Their team assists you in solving all pressure-related problems, and soon it will get fixed.

On the other hand, if you are a beginner and want to resolve this issue yourself, then follow our solutions here.

5 Reasons Why Air Compressor Not Building Pressure

There are 5 types of possible issues that an air compressor owner can face if the pressure won’t build.

Reason 1: Broken Reed Valve

First, we will know about the functioning of the reed valve in an air compressor and then start fixing it.

What is Reed Valve?

A Reed valve is a type of valve that uses a flexible material, usually a thin sheet of metal, to control fluid flow. It is a type of check valve that allows fluid flow in only a single direction.

The reed valve allows, regulates, and prevents the flow of air, steam, vapors, or gases passing through the inlet. It consists of a small, usually cylindrical, metal or fiberglass body in which are incorporated one or two metal reeds.

So, if your reed valve is broken, follow our guide for fixing it below.

Replacing Reed Valve

We will replace the reed valve in 4 following steps:

  • First, empty your air tank to release all the pressure
  • Loosen the 4 nuts on the top and put it off
  • You will see two reed valves there; one or both of them are broken, which is one of the main reasons the air compressor is not building pressure.
  • Place the new reed valve in the place of the defective one
  • Properly tight all the fittings to avoid any leakage
  • Now, start the compressor and analyze the psi rating on the pressure gauge. The pressure will start increasing, and congratulations your problem is fixed

If you have an old air compressor, then there is a possibility that the reed valve has become rusty. In this case, you can clean it with some solvent.

Reason 2: Blown Gasket

A blown gasket may be the issue that many DIY enthusiasts face when their air compressors are not building pressure. It blows due to intense heat in the engine and the unavailability of a cooling system. Basically, Gasket is a seal that helps to get high pressure by blocking the air leakage of contacting surfaces. If blown out or damaged, your compressor will fail to build the required pressure. For checking whether the Gasket is blown or not, you have to open the top section of the air compressor. The Gasket will be available between the valve plate and cylinder. If it is broken or blown, replace it. Now, you can get the desired pressure. 

Reason 3: Seal Leakage

Your central pneumatic air compressor will also not build good pressure if there is a seal leakage issue. Whenever you run the air compressor and the pressure start building, the tank will not fill properly, and after some time all the pressure drops. So to fix it, check all the seals of the compressor, especially those that are connected with the tank area. To check which seal is leaking, follow this DIY guide:

  • Calculate how many seals are on the air compressor; it will help us not miss anyone.
  • Take water in your hand and pour it into the seal area.
  • If there is a leakage issue, bubbles start coming outside; this way you can identify the area where the seal is leaking.
  • Repeat the same procedure on all remaining seals.
  • When you identify the leaking part, try to repair it by applying some adhesive or leakage blocking material.

Hopefully, this quick method will help to find out the seal leakage section, and still if the issue isn’t resolved then try other solutions given here.

Reason 4: Damaged Tank

As the pressure is stored in the tank so if the compressor tank is damaged, it could also be a reason for not building pressure. Run a thorough inspection of the tank, and check if there is a damaged sign on the tank. When you find the damaged area, then try to recover it. The only way to fix it is by welding the area because if you use any other type of solution it will not work. When the internal pressure of the air compressor increases, you can again face the same damage to the tank. So, go for a long-lasting solution and properly fix the damaged area through welding.

Reason 5: Valve Left Opened

The drain valve available at the bottom of air tank helps in removing excess liquid and gas. If it is left open, the air compressor will continue losing pressure, and the pressure won’t build until you fix the valve. So, check the drain valve properly; if it is opened then close it, and if the valve is leaking or damaged, you have to replace it quickly. Now, start the compressor, it will perfectly start building pressure. 


These solutions 100% work and fix your central pneumatic pressure-related problems. For the prevention of these types of issues, you have to do your compressor maintenance after every 80-90 days. It will help to quickly catch the issue if air compressor cause and you can fix it on time. If there is any problem related to your central pneumatic compressor other than listed here, you can comment below; we will quickly respond and resolve your issue.

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