How Do You Troubleshoot Your AC Before Calling a Repair Company?
- Jun 15
- 4 min read
TLDR: Before calling an AC repair company, check the air filter, thermostat settings, circuit breaker, and outdoor unit in that order. These four checks resolve approximately 30% of AC service calls without a technician visit, saving the average $85 to $150 diagnostic fee. If none of these fix the problem, call a licensed HVAC technician.
Before calling a repair company for an air conditioner that is not working, check four things in this order: the air filter, the thermostat, the circuit breaker, and the outdoor unit.
According to the Air Conditioning Contractors of America, approximately 30% of residential AC service calls involve problems that could have been resolved by the homeowner without a technician visit. The average diagnostic fee in Colorado runs $85 to $150. The four-point check takes 10 to 15 minutes.
Homeowners in Arvada who complete this check and still have a non-functioning system can reach Air Conditioner Repair Arvada, CO for licensed diagnosis and repair.
Check 1: The Air Filter
A clogged air filter restricts airflow through the system, causing the evaporator coil to freeze and the system to lose cooling capacity or shut down on safety controls.
How to check: Pull the filter out of the return air slot or air handler cabinet. Hold it up to a light source. A filter that blocks light is restricting airflow.
What to do: Replace it with a filter of the same MERV rating. Restart the system. If ice is visible on the indoor coil, turn the system to "fan only" mode for 30 to 60 minutes to thaw before restarting cooling.
Standard one-inch filters need replacement every 30 to 60 days during the cooling season. A filter that has not been changed in 90 days is a probable cause of reduced performance.
Check 2: Thermostat Settings
A thermostat in the wrong mode produces symptoms that look like equipment failure.
Common thermostat errors:
The system is in "heat" mode instead of "cool"
Fan is set to "on" (continuous) instead of "auto," so air blows from vents even when the compressor is not running, creating a false impression that the AC is on but not cooling
Temperature setpoint is above room temperature, so the system does not activate
Thermostat batteries are dead (on battery-powered models)
How to check: Set the thermostat to "cool," set the fan to "auto," and set the temperature 3 to 4 degrees below the current room temperature. Wait 5 minutes. The outdoor unit should start.
Check 3: Circuit Breakers
AC systems have two breakers: one for the indoor air handler and one for the outdoor condenser. Either one can trip independently.
How to check: Go to the main electrical panel and locate the breakers labeled "AC," "air conditioner," "condenser," or "furnace/air handler." A tripped breaker sits in the middle position between on and off.
What to do: Push the breaker fully to the "off" position, then back to "on." Wait 5 minutes before restarting the thermostat.
If the breaker trips again immediately after a restart, a fault exists in the circuit. Do not continue resetting it. Call a technician. A repeatedly tripping breaker is the system's safety mechanism, preventing a larger failure.
Check 4: The Outdoor Unit
Go outside and look at the condenser unit.
What to look for:
Is the unit running? You should hear the compressor (a hum) and see the fan spinning. If neither is happening, the unit is not receiving power or has a failed capacitor.
Is there ice on the unit or the refrigerant lines? Ice indicates airflow restriction (dirty filter, blocked coil) or low refrigerant. Turn the system off to defrost before assessing further.
Is debris blocking the unit? The condenser needs airflow on all sides and the top. Trim vegetation to maintain 18 inches of clearance on all sides.
Has the unit reset? Many units have a reset button on the side. If the unit does not start, press and hold the reset button for 5 seconds, then attempt to restart from the thermostat.
When Does the Problem Require a Technician?
Call a licensed technician when:
The breaker trips again after resetting
Ice is visible on the refrigerant lines or coil after defrosting and cleaning the filter
You hear grinding, rattling, or banging from the outdoor unit
The outdoor unit does not start despite power being confirmed at the breaker
The system runs continuously, but the room temperature does not drop
These symptoms indicate mechanical or refrigerant system issues that require certification and specialized tools to diagnose and repair. The EPA 608 certification is required to purchase and handle refrigerants. This is not a DIY-repairable category.
What Do AC Repair Technicians Typically Find?
A 2022 analysis of service call data from the ACCA found the most common causes of residential AC failure by frequency:
Dirty air filter (28%)
Capacitor failure (19%)
Refrigerant leak (15%)
Electrical failure at thermostat or contactor (14%)
Compressor failure (9%)
Frozen coil from airflow restriction (8%)
Other (7%)
Items 1 through the first part of item 3 are diagnosable by a homeowner through the checks above. Items 2 through 7 require a technician.
Key Takeaways
Dirty air filter, thermostat settings, tripped breaker, and outdoor unit condition resolve approximately 30% of residential AC service calls without a technician visit
A filter that blocks light is causing airflow restriction and should be replaced before any other troubleshooting
Fan set to "on" instead of "auto" on the thermostat causes continuous airflow from vents even when cooling is not active, creating a misleading symptom
A breaker that trips again immediately after reset indicates an active fault; do not continue resetting it
Ice on refrigerant lines means either a dirty filter (airflow restriction) or low refrigerant, both require the system to be turned off before further action
Capacitor failure is the most common repair-level AC problem at 19% of service calls; it requires a technician and costs $150 to $350
Run through these four checks before calling a repair company. If the problem is in this list, you save the diagnostic fee. If it is not, you give the technician accurate information about what you have already verified, which shortens the diagnostic process.
