Reasons Why Your Portable Air Compressor Won’t Start

By Jack Mash

Machines make us money. They are fast. They get the job done better than humans can.

In construction, air compressors have built more homes than just about any other tool.

However, as machines, they are prone to breakdown and failures. 

Sadly, air compressors belong to this category.

Air compressors, whose primary objective is to increase the gas’s pressure by reducing its volume and transporting it through a pipe, sometimes will not start. 

A thousand and one things could be responsible for its failure to start. 

It’s too easy to assume that your portable air compressor is damaged and needs to be replaced. 

Before you shop for a new portable air compressor, try these tips to get yours going again. 

Power Source Problem

Before speaking in-depth about the power source problem as a cause, we will like to establish the fact that some air compressor runs on fuel. For your fuel-based compressors, you might need to use the pressure relief valve to release the pressure in the tank before starting it. 

A basic awareness of some electrical terminologies will aid your understanding when troubleshooting, but it isn’t a prerequisite.

The first thing first, when you notice that your portable air compressor will not start, check its connection to a wall socket, and ensure to turn the switch on.

The emphasis here is laid on the wall socket because most electrical compressors have power ratings that could be gotten directly from the wall socket. 

It does not imply that you cannot use an extension cord, but if you must do ensure the extension cords are between 10-25 gauge wire. Otherwise enough power may not be getting to the compressor. 

If it is plugged into the wall, check the breaker box. Make sure the breaker is not tripped. 

Capacitor or Relay Problem

Another reason why your portable air compressor won’t start is a faulty capacitor. Having a faulty one on your machine could mess things up. In addressing this issue, an excellent way to do it is by using a hard start capacitor. 

Sometimes you can identify a faulty capacitor by the burn marks it has. Other times you’ll need to test it with a multimeter that can measure micro-Farads. (such as an HVAC Multimeter.)

A hard start capacitor performs the function of adding to the starting torque of the air compressor and cutting out the capacitor from the circuit once the machine has started.

For the proper operation of your air compressor, a broken capacitor will need to be replaced. This replacement is an effective way of solving a broken capacitor problem.

If the start relay is the problem, then you will want to consider replacing it to bring your machine back to operation.

The Circuit Breaker Trip-Off

Electromechanical equipment has a circuit breaker. This circuit breaker serves to protect the equipment against a power surge that could damage some components of the device. The circuit breaker trips off to cut out the power supply during excessive high voltage. 

Some old houses don’t have a breaker. Instead, they use a fuse box. If the fuse is blown, you have to unscrew it and screw in a replacement fuse. 

After you ensure that enough current flows from the wall socket, you will need to be sure that an in-line fuse in the compressor is not bad.

Check all wire connection of the air compressor to be sure there is no short.

The inline fuse is generally designated by a thicker spot in the wiriing. If you pull back the cover in this area you can access the fuse.  

Faulty Pressure Switch

The next possible reason why your portable air compressor won’t start is a faulty pressure switch. You could take the following steps to troubleshoot your pressure switch.

First, ensure your compressor is unplugged from power, then you can twist open the drain valve to release air from the compressor.

After bleeding air from the tank properly, get someone to reconnect the compressor to power, and turn on the pressure switch. You should hear a ‘click’ sound from the pressure switch.

The solid click should indicate the pressure switch is adjusting out and allowing the points to engage. Sometimes, however, there will be a gauge on the pressure regulator. If the gauge is stuck, it can indicate a bad regulator that does not allow the compressor to engage. 

Low Compressor Oil

Air compressors that use oil may have a safety mechanism that disengages the compressor if the oil levels get too low. 

 The oil functions to lubricate the mechanical parts of the air compressor. When this oil level goes below the standard, the compressor may not start. 

This phenomenon is common with mechanical systems. They will not turn on when their oil level is below the specified level, to protect the machine from danger.

You should ensure that the oil level is up to gauge, and your air compressor is not tilted. You could have enough oil in the machine, but because it leans to one side, your air compressor may not start. Ensure you check beneath the oil tank for leaks.

Also, do a routine check on the viscosity of the oil inside of your compressor. In cold weather, a thicker viscosity oil may prevent the compressor from running. In these conditions, you may want to switch to a 10W oil during the cold winter months. 


We understand that having a portable air compressor that won’t work can be very frustrating and annoying. 

With this guide, we hope that we can help your compressor get started again and save you money.  

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