AC Not Cooling in Aurora? 7 Fixes Before You Book a Service Call
A licensed Aurora HVAC tech's checklist for a central air conditioner that runs but will not cool — filter, drain, capacitor, refrigerant, and when to stop DIY.
It's 92°F in Aurora, the thermostat says 78, and the house is at 84. Before you call, run this checklist — half our July no-cool calls are solved in five minutes at the panel or filter.
1. Change the filter
A restricted filter starves the coil, freezes it into a block of ice, and cuts cooling to zero. If you can see dust caked on the filter, replace it. If the indoor coil is already frozen, turn the system to Fan Only for 60 minutes to thaw before running Cool.
2. Check every breaker and switch
There are usually two breakers — one for the outdoor condenser, one for the indoor air handler — plus a disconnect box next to the outdoor unit. All three must be on. Trip and reset any that are questionable.
3. Confirm the outdoor unit is running
Walk outside. If the fan on top of the outdoor unit is spinning and you feel warm air blowing out, the condenser is working. If it is silent, that is a capacitor, contactor, or motor failure — needs a tech.
4. Clear the condensate drain
Every AC generates condensation. If the drain line clogs, a safety float switch shuts down the system to prevent water damage. Find the PVC drain line near the air handler and clear it with a wet/dry vac at the exterior end.
5. Rinse the outdoor coil
Cottonwood and dust plug the outdoor coil fins fast in the Denver metro. Kill power at the disconnect, hose the outside of the unit gently from the inside out. Never use a pressure washer.
6. Verify the thermostat settings
Mode: Cool. Fan: Auto (not On — On runs the blower constantly and blows warm air between cycles). Setpoint at least 4°F below current room temp. Dead batteries in a battery-powered stat will let it display normally but not call for cool.
7. If the copper line is warm — you need refrigerant
The larger insulated copper line coming out of the outdoor unit should be cold and sweating when the system runs. If it is warm or dry, you are low on refrigerant, which means there is a leak. That is a licensed job — Colorado law requires an EPA-certified tech to add refrigerant.
Still not cooling? Book a service call
Ventilation Pro Mechanical runs same-day AC service calls across Aurora, Denver, Centennial, Parker, and Littleton. We diagnose the exact problem and give you the repair number before we touch anything. Call 720-256-5118.
Why is my AC blowing warm air?
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Most common causes: frozen indoor coil from a clogged filter, low refrigerant from a leak, tripped outdoor breaker, or a failed capacitor keeping the compressor from starting.
How much does AC repair cost in Aurora?
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Capacitor and contactor replacements are typically a few hundred dollars. Refrigerant leaks, compressor issues, and full recharges cost more. We diagnose first and quote before doing the work.
Should I run my AC continuously in Denver summer?
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Leave the thermostat at a steady setpoint (75-78 works for most homes). Cranking it up and down uses more energy than holding a set temperature.
How long should a central AC last in Colorado?
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12 to 18 years with maintenance. Our dry air is actually kinder to AC equipment than humid climates.
AC, furnace, heat pump, or ductwork trouble in the Denver metro?
Same-day service across Aurora, Denver, Centennial, Parker & Littleton · Free install estimates · Licensed & insured.