Compressor Will Not Start When Cold

The air compressor runs properly during the late spring, summer and early fall. But, the air compressor will not start when cold. How come?

To understand this compressor problem it helps to understand that 120 VAC air compressor motors run very close to the line when it comes to the available power in a 120 VAC supply circuit and the amount of power that is actually needed for the air compressor motor to start and run.

Air compressor motors typically will not start without help, and that’s where the start and run capacitors come into the picture. For more info on them see the page about – is the compressor start capacitor working – on this site.

In the northern and southern parts of the world we get this phenomenon called snow. If there’s snow, there is cold weather, and our air compressors get just as cold as the weather when they are stored in an unheated area, like the compressor in the photo, just brought out of a cold garage.

compressor will not start when cold - cold air compressor

Compressor Will Not Start When Cold

Why? The typical reason the air compressor will not start when cold is the compressor oil.

If your air compressor is an oil lubricated model, what happens to oil when it gets cold? It becomes thicker, more viscous, and since the oil is thicker, it moves sluggishly and is harder to move.

Compressor lubricating oil had splashed up into the pump of the compressor when it was last running, and now that oil is close to, or is, frozen solid.

So you have this cold air compressor with cold, thick and maybe frozen oil. Your air compressor is already marginal when it comes to the power available when it is starting in warm weather.  Further creating this issue is that the compressor operation may now not be optimal since it’s no longer new. And, it may be frozen.

The additional load on the motor by the thickened oil  means the motor cannot turn over, you may get a fuse blown or a breaker lets go, and at the least, the compressor will not start when it is cold.

What About Non-lubed Air Compressors

Air compressors that are oil-less, or are labelled as non-lube, are actually factory lubed – in theory for the life of the compressor – and there is not need for the compressor owner to add oil.

However, these air compressors still contain factory lube, and the same phenomenon can result. Frozen or chilled lubrication adds load to the compressor start circuit, often to the point where the compressor cannot start.

Solution

Bring the compressor indoors a few hours before you want to use it. Let it warm up to room temperature, and then plug it in and/or turn it on if yours  has an ON/OFF compressor switch.

That should do the trick, assuming that trying to start it when it was cold hasn’t created another compressor start problem that is not related to the compressor temperature.

Comments

  1. tony nguyen says:

    The quickest and most logical solution for your air compressor is for you to heat things up. Place the entire ensemble in a heated space and leave it there for more than an hour. The mechanical segments as well as the compressor’s start-up circuit will have warmed sufficiently and the oil will have melted again. Your ‘winter’ is over.

  2. len meeny says:

    I have been given an Airline 2.5 hp compressor that started up first go today. But when I went out to it later, it would not start. Can anybody please help me out? I need the compressor to start spray painting my 1928 Dodge.

  3. Brandon says:

    Hey guys. I have an old Campbell Hausfeld 15 gal portable electric air compressor. The compressor will cut on and cut off at about 40 psi and will not refill after I let all the air out. I replaced the pressure switch and it will air up to about 100 psi then cut off. When I let the air out of the tank it will not cut back on to refill the tank. Any idea what’s wrong with this thing?

    • Hey Brandon. If the compressor stops at 40 PSI, and will not start after you drain the tank, it’s logical that the pressure switch would be suspect. The fact that the compressor gets to 100 PSI after adding a new switch is more than a little odd. We think this is pointing to an electrical issue with the motor circuit, and suggest that you see the page on this site about how to check your compressor motor capacitors. They might be getting a bit wonky, and if they aren’t working right, the symptoms would be similar to your compressors, particularly in its capacity to handle increasing load.

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