If the air coming from your vents is getting warmer and the outdoor AC unit is silent, start with a few simple checks. The problem may be at the thermostat or breaker rather than the compressor itself.
In Phoenix, you do not want to spend half the day guessing while the house gets hotter. Check the items below first. If they do not get the outdoor unit running, Wolfgangs offers AC repair for homeowners in Phoenix, Tempe, and Prescott Valley.
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Quick Checks Before You Call a Technician
Before assuming the compressor has failed, check these three things:
- Breaker: Find the breaker marked for the AC or outdoor unit. If it has tripped, reset it once. If it trips again, leave it off and call a technician.
- Thermostat: Make sure it is set to COOL and the temperature is set below the current room temperature. Replace the batteries if your thermostat uses them and the display is blank or weak.
- Outdoor disconnect: Look at the disconnect box mounted near the outdoor unit. Make sure the visible switch or handle has not been turned off. Do not open the box or touch anything inside it.
If those checks do not solve the problem, the next steps require testing inside the AC.
Common Reasons an AC Compressor Won't Start
When we arrive for an AC compressor not turning on, we first find out if the compressor is actually the failed part. Several electrical and control problems can keep it from starting.
Common causes include:
- Tripped breaker or blown fuse: An electrical fault can cut power to the outdoor unit.
- Failed capacitor: Depending on the system design, a capacitor may help the compressor, fan motor, or both start and run properly.
- Thermostat or control problem: The cooling call may not be reaching the outdoor equipment.
- Failed contactor: The contactor controls power to parts of the outdoor unit. If it fails, the compressor may not receive power.
- Compressor failure: Internal electrical or mechanical damage can keep the compressor from starting.
Finding the cause requires electrical testing. Do not remove the outdoor unit's access panel to troubleshoot these parts yourself.
Compressor Hums But Won't Start
A hum tells us the outdoor equipment is trying to do something, but it does not tell us which part has failed. A weak capacitor is one possible cause. A compressor that is struggling to start can make a similar sound.
Turn the AC off instead of letting it sit there humming. We can test the capacitor, electrical components, and compressor to find out what is preventing the system from starting.
Why This Is More Urgent in Phoenix Than Elsewhere
During a Phoenix summer, losing the outdoor unit means the house can start gaining heat while temperatures outside are above 110 degrees. During extreme Phoenix heat, a home without cooling can become uncomfortable or unsafe more quickly, especially for young children, older adults, pets, and people who are more vulnerable to heat.
Long summer run times are hard on AC electrical components, and monsoon dust can collect around the outdoor equipment and restrict airflow. If your AC stops during extreme heat and you need help right away, our 24-hour emergency cooling service is available for urgent cooling problems.
When to Call for Professional Repair
Stop troubleshooting and call us if the breaker trips again, the outdoor unit hums without starting, you smell something burning, or the quick checks do not restore cooling.
At that point, we need to test the electrical components and compressor. Capacitors and other parts inside the outdoor unit can hold dangerous electrical charges even after power is shut off, so this work belongs with a trained technician.
If testing confirms that the compressor has failed, we look at the age and condition of the AC along with the repair involved. On a system with other major wear, we can compare the compressor repair with AC replacement costs before you decide where to put the money.
Get Your AC Back Up and Running Today
If the breaker, thermostat, and disconnect all check out but the outdoor unit still will not start, you have reached the point where the equipment needs to be tested.
Wolfgangs handles AC repair in Phoenix, AZ, along with Tempe and Prescott Valley. We will find out why the outdoor unit stopped and explain what needs to be repaired before any work begins.
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FAQ
Why is my AC compressor not turning on at all?
The outdoor unit may not be receiving power, or a capacitor, contactor, control component, fan motor, or compressor problem may be preventing the system from starting. If the breaker, thermostat, and outdoor disconnect are set correctly, the system needs professional testing.
Is it safe to reset the breaker myself?
You can reset the AC breaker once if there is no burning smell or visible damage. If it trips again, leave it off and have the system checked.
Can a dirty outdoor unit stop the compressor from starting?
Heavy dirt and debris can restrict airflow and make the outdoor unit run hotter. A compressor that will not start still needs testing to determine the actual cause.
How much does compressor repair typically cost?
The cost depends on what has failed. A capacitor or other electrical repair is a different job from replacing a failed compressor, so the system needs to be diagnosed before the repair cost is known.
Should I repair or replace a failed compressor?
That decision depends on the AC's age, condition, and other needed repairs. If the system has significant wear, compare the compressor repair with replacement before putting money into the existing equipment.
