Guide
The AC is running, but the air is warm
A system that runs without cooling is one of the most common summer calls. Some causes take a minute to rule out. Others need a technician with gauges.
Work through these in order
Stop at any step that turns up the answer.
Thermostat mode
It should say Cool, not Heat, Fan or Auto with a high set point. A fan set to On blows room air even when the compressor is off.
Batteries and display
A faint or blank screen can mean the thermostat is not calling for cooling at all.
The filter
Slide it out and hold it up to a window. A filter that blocks the daylight needs changing.
Breakers
There are often two: one in the main panel and one in the disconnect box beside the outdoor unit. Reset a tripped one once.
The outdoor unit
With the system calling for cooling, the fan on top should spin and you should hear the compressor. Silence, or a hum with no fan, points to a part failure.
Registers and returns
Make sure furniture or rugs are not covering return grilles, and that most supply registers are open.
What the results usually mean
If the outdoor fan runs but the air stays warm, the compressor may not be starting, or the system may be low on refrigerant. If neither the fan nor the compressor runs, the cause is often electrical: a capacitor, a contactor or a control fault.
If the copper line at the outdoor unit is frosted or iced, the coil inside has frozen. Turn the system off and let it thaw, and read the frozen coil guide before turning it back on.
Hot afternoons are a stress test
Some systems cool well in the morning and fall behind by late afternoon. On a 105-degree day, a system that is slightly undercharged, has a dirty coil or was sized tight to begin with will show it first. If the house recovers after sunset, mention that pattern on the call. It helps narrow the cause.
What not to do
Do not keep resetting a breaker that trips again. Do not open the outdoor unit's electrical panel. The capacitor inside holds a charge even with the power off. Do not add refrigerant from a store-bought can: refrigerant work on these systems belongs to EPA-certified technicians.
Common questions
How cool should the air from the vents be?
Contractors look at the difference between the air going into the return and the air leaving the supply registers. Ask what number they expect for your system; a much smaller difference than normal points to a problem.
Could it be the ducts?
Yes. A disconnected or crushed duct in a hot attic can dump cooled air where it does nothing. Rooms at the end of a long run are usually the first to feel it.
Talk it over with a contractor
Say what the system is doing and where the house is. You will be speaking with an independent HVAC contractor who works in Bakersfield and the towns around it.