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Is your ac compressor not working, but the fan is running? There are quite a few issues that could prevent your compressor from running. These issues can range from ‘easy to fix’ to more complex ones that can require a licensed Technician to come and have a look.
Some reasons your compressor is not working, but your fan is running include: a bad compressor capacitor, bad starter relay, low refrigerant levels, power issues, bad thermostat wiring, bad contactor, and a dead compressor. Shortly, we’ll be looking at these issues in a little bit in detail.
Air conditioners are typically installed with two fans. One fan that is installed inside your home blows air throughout your home, and the other one found in the ac condenser unit blows away heat from the coils.
Let’s now look at what can cause your compressor not to run when your fan(s) are running.
Read also: Home AC Compressor Not Turning On [Solved]
Why Is My AC Compressor Not Working, but Fan Is Running?
Your AC system has two fans so let’s start by looking at what can cause your indoor fan to run when your compressor unit is not working. Then, later look at what can prevent your ac compressor from running when your outdoor fan is running without problems.
Case #1: AC Compressor Not Working, but Indoor Fan is running
If you have an ac compressor that is not working but your air handler fan is running properly, look out for the following things:
1. Problems With Power
Power and electrical-related issues are common causes for your ac compressor not working. When your compressor and the whole condenser unit is not turning on, this is a clear sign of a power issue. To troubleshoot and fix power issues, you should start by checking the following things:
- Circuit breakers and power switches for both the outdoor and indoor units. Check the air conditioner circuit breaker and verify that it is not tripped. Reset the tripped breakers. If the breaker trips again, you need to call in HVAC professionals.
- Suppose the disconnect is pulled out. A disconnect is a small device planted on the wall of your house near the refrigerant lines. It acts as a switch to cut off power from your condenser unit for any reason you have. A disconnect can also cut power if inserted upside down or in another way. If everything is fine with it, let’s move to the next step.
2. Bad AC contactor
A defective ac contactor can be why your compressor is not turning on. A contactor conducts electricity to all other components of your condenser unit. It has a coil inside and can get magnetic when there is a signal to do so.
When the coil inside the contactor gets burnt out, it will not close the circuit, and the condenser unit will be cut off from power. Meanwhile, your air handler inside will not be affected, and the fan can be running quite fine.
To rule out an ac contactor, get a screwdriver and manually push a metal plate against the other to complete a circuit. If the unit starts running, then the problem is with the contactor. If it doesn’t, then something else could be messing with you. At this point, you need to look at your compressor capacitor.
3. Bad Compressor Capacitor
A defective compressor capacitor could be why your ac compressor is not turning on. A capacitor is an important part of your ac condenser unit because it powers your compressor and fan motor. A defective capacitor is the most common among the top issues that can stop your compressor from running.
The good part is compressors are usually cheap to buy and easy to fix. Just make sure before touching the capacitor you discharge it of all voltage.
Sometimes, you can tell when a capacitor is defective if it has a swollen top but other times, there could be no signs at all. In this case you will need a multimeter to test it for continuity.
4. Bad Thermostat Wiring
A thermostat that is not properly wired can fail to make cooling calls to your HVAC system. This could be why your compressor isn’t working. Pull off your thermostat from the wall and check its wiring.
Make sure there is a jumper between R terminal(power) and the Rc terminal (power for cooling). Without Rc terminal connected, your compressor won’t turn on to start cooling.
Other thermostat issues that could affect the working of your compressor include thermostat settings. For your AC compressor to start running, your thermostat must be adjusted to a temperature lower than the room temperature reading.
5. Low Refrigerant
If the refrigerant leaks out of your ac system, the low-pressure switch will detect this and can shut off the compressor over at the contactor. The low-pressure switch ensures that there is enough refrigerant in your ac system.
6. High-pressure Switch
The high-pressure switch will shut off the compressor if it detects high pressure in your system. That is if the condenser can’t eject heat for some reason, like when it’s blocked or has lots of build-up on it. If the fan motor is defective, much of the heat absorbed from your home won’t be ejected, and the pressure will rise and cause the high-pressure switch to kick in and discontinue the pressure from rising.
Case #2: AC compressor Not Working, but Outside Unit Fan is Running
Sometimes, you might notice a compressor that is not working, but your condenser fan is working without issues. Most of the time, the problem is caused by a dead compressor capacitor.
A dual ac capacitor powers your compressor on one side and your fan motor on the other side. If one side that powers the compressor becomes defective, your compressor won’t work but your fan will run.
In that case, you need to replace your ac capacitor. Compressor capacitors these days are readily available in the market. If you are not comfortable doing all the stuff yourself, call professionals for help.
Bad Starter Relay
A starter relay works in hand with a capacitor. It transports the energy from the capacitor to your compressor. In cases where your starter relay becomes defective, it won’t send energy to the compressor to start running.
A Dead Compressor
Over time, your ac compressor can age and pass its life span. Usually, a compressor can work for about 10-15 years. But if you have been taking care of it well, it can stay a little bit longer than that. However, when it dies, that’s it. Compressors are expensive to replace. If yours dies, consider replacing the whole system.
The general rule of thumb is if replacing your compressor or other parts of the ac system costs more than 50% of the amount you would spend to get a new HVAC system, replace the whole system.
If an ac compressor is not working, but the fan is running, try out our tips in this guide. But if you can’t figure out or solve the problem, it’s best to call professional services.
We’d also advise you to have your air conditioning system checked and maintained regularly. You can have scheduled maintenance in the fall and spring. This will ensure your system is running in the best condition and prevent unforeseen problems. Thanks for reading.
HVAC tech with over 30 years of experience. Retired and doing repair work on the side around Madison County, AL.