Compressor Will Not Start Cold

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So, the air compressor will not start when it is cold? Or, if it starts at all, it starts sluggishly. This can happen when the compressor is a oil-lubricated model and it’s cold where the compressor is!

If the compressor is stored in an uninsulated garage or other outbuilding when the outside temperature drops into the low 40’s (F), or even colder, for example.

When it's cold enough to freeze you it's cold enough to freeze the air compressor too!
When it’s cold enough to freeze you it’s cold enough to freeze the air compressor too!

Marginal Electric Compressor Motors Are Part of the Reason

Many DIY type oil-lubricated air compressors have marginal electric motors. By that I mean that the motors are often as big as they can be to even run on a 120 VAC circuit, and without the added juice from a start capacitor to overcome the inrush startup requirement of the motor, the circuit breaker would pop all the time when the compressor motor tried to start. That is when the temperature is nominal, usually mid-fifties or so (F) or higher. The capacitor and power supply, working together, can get the compressor motor running every time, unless there is a mechanical or another electrical issue.

What Happens When You Chill The Compressor?

Now, let’s take that same compressor and put it in the unheated garage. And, it is mid-January in North Dakota, for example. Think it is going to be cold in that garage?

What is an oil-lubricated compressor lubricated with?

Oil, you answer! And, you already know what happens to oil when it gets cold, don’t you? The colder it gets, the more that oil thickens. If it is cold enough, that oil will freeze almost or completely solid.

Now, you have the internal workings of your air compressor essentially stuck in a cold, thick oil mass, and you throw the switch to start it up.

What Happens When You Plug In the Compressor?

Either nothing at all happens, or, depending on the fuse delay, your breaker or fuse will likely pop.

Your air compressor is trying to start. It just cannot get enough oomph out of the supply circuit, even with the capacitor kicking in its charge, to start the motor turning against the added load of the frozen or thickened oil. The compressor motor continues pulling more amps in trying to start when so very cold, until the circuit breaker or fuse lets go.

You know how difficult it is to start your car on sub-zero days? Your oil-lubed, and even some non-oil-lubricated models will respond to the cold the same way.

If you are having a problem getting your air compressor to start when it is really cold, warm it up! Bring it into a heated area for an hour or so before you need to use it.

Both your compressor start circuit and the mechanical parts of the air compressor will thank you for it.

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