Craftsman Air Compressor Will Not Start

Do you own a Craftsman air compressor. What do you do when the Craftsman air compressor will not start? We hope the following helps.

First Step When a Craftsman Air Compressor Will Not Start

The first step is always to check and make sure the socket into which your compressor is plugged actually has power there. We are talking about compressors that are typically plugged into a 120 VAC circuit here, but the same principle applies regardless of the power source. Is there power to your compressor?

Craftsman air compressor will not start - typical fuse and breaker for electrical supply

Always check the fuse or breaker first to ensure that you have power to the outlet for the air compressor.

Sometimes, when compressors are hard to start, the starting process may have popped the breaker or blown the fuse in the power supply to that outlet.

Simply grab another electrical device that you know is working and plug it into the same outlet the your air compressor is commonly plugged into. If the device works, then you have power there. If it doesn’t – your circuit fuse or breaker may have popped. Check that out and if there isn’t power to the outlet, either use another outlet with power, or reset the breaker or replace the fuse to get power to the compressor outlet.

It’s always useful too to have your air compressor plugged into an outlet that is protected by at least a 15 amp, and preferably a 20 amp breaker or fuse.

If there was power at the outlet and the compressor won’t start, move to step two. If you turn the compressor on again, it may start, it may not – and it may blow the fuse or breaker again. If that happens, replace the fuse / breaker with the compressor unplugged from that circuit, and move to step two.

Second Step When a Craftsman Air Compressor Will Not Start

The following information is applicable to pretty much all brands of air compressors that come equipped with an air tank.

We always suggest this as the first step when trying to find out what is wrong with an air compressor when it won’t start.

Unplug the air compressor, open the tank drain valve, and drain all the air out of the compressor tank. At the same time, you will be voiding the tank of any water accumulation, something you should do on a regular basis anyway.

Sometimes the crud that comes out of the tank with any water is pretty dirty. You may want to open the tank drain with it sitting on some old newspapers or cardboard to catch the water sludge mixture. If you have not drained your tank in a long time, there may be quite a bit of water. So, be aware.

Why drain the compressor tank?

By draining the compressor tank fully you ensure that the effect of the air pressure on the pressure switch has been removed. As a result, the compressor pressure switch should have tripped to “passing”, meaning that power should now be flowing across the pressure switch to the motor circuit.

Tank drains are typically located on the bottom of the lowest part of the tank. One such can be seen in the following image of a small Campbell Hausfeld air compressor. The red arrow points to the tank drain.

Drain the compressor tank - tank drain location on a Campbell Hausfeld air compressor

Another reason to drain the compressor tank is that your typical home air compressor usually has some sort of unload device that voids any air trapped over the piston when the air compressor stops. Trapped air will make it very hard for the air compressor to restart. Emptying the tank will emulate the function of the unloader valve, ensuring that no air is trapped over the piston, and eliminating this as a reason why your Craftsman air compressor will not start.

Close the tank drain, and plug the air compressor back in. Assuming that the ON/OFF switch is flipped to on (if your Craftsman air compressor has a switch) the compressor should start.

No joy?

What’s next when Craftsman compressor won’t start?

It would be useful to know if there were any sounds from the air compressor at all, when you tried to start it.

So far we’ve checked to see if we have power to the compressor, and tried to start it after draining the tank.

Does power at the plug mean power to the compressor motor?

Step Three – Does the ON/OFF button work?

If your Craftsman air compressor comes equipped with an ON/OFF button it needs to be checked to ensure that, even though you have power flowing to the Craftsman air compressor from the wall outlet, that the power is not being stopped by a malfunctioning ON/OFF switch.

Typical compressor ON/OFF switch

Typical air compressor ON/OFF switch

The easiest way to check the ON/OFF switch is with a multi-meter that can check voltage. Probe the supply line (the one from the wall plug) at the switch to confirm that power is making it to the switch. Then, use the multi-meter to check the voltage on the compressor side of the switch, with the switch turned on.

Yes, this is a live circuit and you very much need to be careful. If probing live wire is not for you either do not do it and get a pro to work on your compressor, or method two may apply.

Method two: Unplug the compressor, and examine where the wires enter and exit the ON/OFF switch. Typically there will be one wire on each terminal on the switch. Often they are connected to the switch by simple push on or plug connectors. If so, pull off both wires, hold the plug ends together so metal touches to make a circuit, and use a piece of electrician’s tape to hold the ends together. Make sure that the wires are not, and can not touch anything else than each other.

Why tape the ON/OFF switch wires together?

What you are doing is taking the ON/OFF switch out of the circuit. When you plug the air compressor back in, the power will run right by the switch to the next item in the circuit. We’ll cover that in just a moment.

OK, if the Craftsman starts now, then it’s most likely that the switch has failed, and it either needs to be replaced, or left out of the circuit entirely. It’s your call.

If your air compressor comes with an ON/OFF switch and a pressure switch, really, the ON/OFF switch is redundant. If the pressure switch is working, then the pressure switch will turn off the compressor motor when the tank is full, and your air compressor will stay off unless the pressure in your tank drains down far enough that the pressure switch trips and the compressor will restart. The tank may drain down due to a leaking tank check valve or leak in a fitting in the line.

We don’t use compressor ON/OFF switches on our compressors but let the compressor shut off due to the tank being full, we pull the compressor power plug, and then drain the tank a bit to let moisture blow out. Next time we need air, we simply plug the compressor back in and carry on.

Does the Pressure Switch Work?

Earlier we talked about draining the tank to ensure that the pressure switch should trip to passing to allow power to cross the points and enter the motor circuit. Ensure that the compressor tank is empty and that the air compressor is plugged in to a live outlet.

Air compressor pressure switch with unloader valve.

Air compressor pressure switch with unloader valve.

In the image above we see a typical air compressor pressure switch, this one with an external unloader valve. You will need to remove the cover of the switch, and use a multi-meter to check whether there is power on both sides of the switch. That is, 120 VAC showing up on the line side of the switch, and 120 VAC showing up on the load or motor side of the switch.

As always be careful. When you remove the cover the terminals inside the switch will be live, and if you are careless and ground yourself when probing them, you will do yourself a damage – perhaps even fatally! Don’t do this if you are not comfortable with the process.

For purposes of this page, let us assume that find that although you have power on the supply side of switch you do not have power on th eload / motor side of the switch. That suggests that your pressure switch has failed and a replacement is in order. Please see the page on this site about replacing the pressure switch for details about that.

Or… you have used your multi-meter and find that you have power on the supply / line side of the pressure switch terminals, and you have power on the load / motor side of the switch too. This suggests that the pressure switch is working just fine, and it is not likely that the pressure switch is the reason your Craftsman air compressor will not start.

Now what?

We now have to continue to follow the power. See is the start capacitor working?

Comments

  1. I have a 60 gallon craftsman and the motor will only run when you cover the air intake. If left uncovered the motor only hums. Any thoughts?

    • Now that is bizarre. You can see the page on this site that talks about why air compressors hum when they are trying to start for information about that. Covering the intake (essentially increasing the load on the motor) allows the motor to run, but uncovering the intake (essentially reducing the motor load at start up) makes the motor hum. Still, if it turns out that it’s not the start capacitor – you need to check it – then our next best guess is a valve failure.

  2. I have a Craftsman 5.5hp (supposedly). Starts easily on 20 amp circuit when tank is empty. When using air tool and it gets to cut in pressure it trips the breaker. I tested the start capacitor to 412mf. It should be between 400 and 480. I replaced the pressure switch and unloader valve. After initial fill, and at cut off, I do hear the unloaded valve releasing the pressure to the pump head. Still trips breaker at cut in.

    Is it possible the check valve has failed and is slowly building pressure back onto the pump head causing a load on the motor on cut in? Or would it be better to get a new start capacitor since its testing on the low end of the rating?

    • Has the check valve failed? Possibly. With an empty tank and the compressor off, you can remove and examine, clean it, and replace the tank check valve to be sure. If the compressor cord is right in the wall socket, and there isn’t too much other load on the circuit feeding the compressor, yeah, a new start cap is a good diagnostic, and if it turns out to be the motor instead, then you’ll at least have a spare. Let us know how it turns out, please?

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