Leonard Splaine Why is my Outdoor AC unit’s fan not spinning

The heat of summer can be intense, and you need a reliable air conditioner to provide relief indoors when it’s too hot and humid to be outside.

Unfortunately, air conditioners can break down for a number of reasons – leaving you to sweat it out while you search for a reliable HVAC company to make the repair.

In some situations, you noticed that your air conditioner’s condenser fan stops spinning, even though the actual system is running. Does this sound familiar?

If so, you’re probably wondering what’s going on.

There are two possible scenarios here:

• Scenario A: You hear the outdoor unit’s compressor working and the fan isn’t spinning.
• Scenario B: You don’t hear the outdoor unit’s compressor working and the fan isn’t spinning.

Let’s explore both.

Scenario A: Compressor works, but the fan does not spin

Oh, no—your air conditioner’s not working. You go outside to check the A/C unit, and it’s buzzing but the fan’s not spinning. What’s going on?

The Problem:  You may have a bad fan motor and/or bad start capacitor.

A capacitor is a small, cylindrical object that stores a lot of energy—similar to a battery. Capacitors send an electrical jolt to start a motor (a “start capacitor”) or to keep one running (a “run capacitor.”) In an air conditioning system, capacitors work with three different motors: the compressor, the indoor blower fan, and outdoor fan.

The good news is, it’s pretty easy to find out. A bad capacitor is a common A/C problem with a straightforward fix.

Here’s an easy way to test if the fan’s capacitor is bad:

Slide a long, thin wooden stick through the fan grate and gently push one of the blades to try to get the fan spinning. (Safety note: DO NOT use any kind of conductive metal or material to do this. Don’t put your fingers in or near the grate.)

If the fan takes off and then keeps going on its own, you more than likely have a bad start capacitor. You took over its job of kick-starting the fan by pushing the blades.

If the fan doesn’t start running, you may have a bad fan motor. If you have difficulty getting the blades to turn, there may be debris wrapped around the fan axle, or the motor bearings may be dirty or jammed.

Okay, my capacitor is bad. Now what?

Turn off the A/C unit and call in an HVAC technician to replace the capacitor as soon as possible. This is a quick and simple repair for a professional.

If you leave the unit running, the fan motor will keep attempting and failing to start. The capacitor may also be used to keep the fan motor running properly as well as starting it. (This is called a “start/run capacitor” and they’re used in many A/C systems.) In either case, a bad capacitor will strain the fan motor and may cause it to burn out completely.

Depending on your A/C unit, the same capacitor may be used for both the fan motor and compressor. This is called a “dual capacitor” and has three terminals on the top—one for the fan motor, one for the compressor, and one shared. Your compressor can overheat if it continually attempts to access a failed capacitor, causing major damage.

Don’t risk a costly fan motor or compressor repair by putting off a simple capacitor replacement!

Scenario B: Both compressor and fan are not working

The compressor is an integral part of the air conditioning system. Its role is to carry heat out of the house while compressing the refrigerant fluid.

The Problem: When turning on the AC, you may notice the fan running when the compressor is not. In most cases,  either no power is getting to the outdoor unit or you have a defective compressor contactor. If your AC compressor is not functioning, here are some situations you may face:

• Warm, dry air coming from the running fan.
• The circuit breaker keeps tripping.
• The compressor stops altogether.
• Strange noises and shaking from the outdoor unit.

Solution:

Check the circuit breaker box. Did your outdoor unit breaker trip? If so turn off your AC at the thermostat, then reset the breaker. Turn the AC back on at the thermostat, If the AC trips the breaker again, then call an HVAC expert.  An expert AC technician will make a recommendation of whether to replace or repair the compressor. A pro in the industry can fix it before the utility begins to rack up.

Still have AC problems?

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