Our phone does not ring evenly through the summer. It rings in clusters, and the clusters land on the hottest three or four days of the year. That is not a coincidence, and it is not bad luck. A heat wave is a stress test, and marginal equipment fails the test.
Here is what is actually happening inside these systems, what warns you first, and what you can do while you wait for a technician.
Why 105 degrees breaks what 85 degrees did not
An air conditioner rejects heat from inside your house to the air outside. The hotter it is outdoors, the harder that job gets. Refrigerant pressures climb, the compressor works against more resistance, electrical components run hotter, and the system stops getting the off cycles it normally uses to cool itself down. A unit that was quietly limping along at 30 percent airflow restriction all spring has enough margin to keep up at 85 degrees. At 105 it does not.
In other words, the heat wave rarely causes the problem. It reveals a problem that was already there.
What actually breaks
Capacitors
This is the single most common heat wave failure we see. The run capacitor gives the compressor and fan motors the electrical kick they need to start and keep turning. Heat degrades them, and when one weakens the outdoor fan may not spin, or the compressor tries to start, draws heavy current, and trips the breaker. Symptom: the outdoor unit hums or clicks but the fan sits still.
Frozen evaporator coils
Restricted airflow or low refrigerant causes the indoor coil to drop below freezing and build ice. Ice blocks airflow further, which builds more ice. The result is an air conditioner that runs constantly, blows weakly, and cools nothing, often with water dripping somewhere it should not.
Dirty condenser coils
The outdoor coil is how your house gets rid of its heat. Cottonwood fluff, grass clippings, dust, and orchard debris pack into the fins and insulate it. The system then runs hot, long, and inefficient, and eventually protective controls shut it down or the compressor gives up.
Refrigerant leaks
Low refrigerant is a symptom, not a cause. Systems do not consume refrigerant, so if a system is low there is a leak. During a heat wave low charge means poor cooling capacity right when you need maximum capacity, plus compressor strain that shortens equipment life.
Contactors, wiring, and control boards
Contactors pit and weld themselves closed, connections corrode, and boards fail under heat and repeated high-current starts. These are the failures that leave a unit running nonstop or refusing to respond to the thermostat at all.
Drain lines
Hard-working systems pull a lot of condensate. A clogged drain line backs water into a pan, trips a float switch, and shuts the system off as designed, or worse, spills into a ceiling.
Warning signs in the weeks before failure
- The system runs noticeably longer to hit the same thermostat setting than it did last year.
- Weak airflow at the registers, or air that is cool but not cold.
- New noises: buzzing, humming, grinding, or a rattle from the outdoor unit.
- The breaker trips once and resets fine. That is not a fluke, that is a warning.
- Water or ice anywhere on the indoor equipment or refrigerant lines.
- Rooms that always used to keep up and now do not.
- A power bill climbing while your habits have not changed.
Any one of those found in May is a repair. The same one found on the second day of a heat wave is an emergency call at the worst possible time.
What maintenance actually prevents this
A real tune-up is not a filter swap and a handshake. It includes washing the condenser coil, checking refrigerant charge against manufacturer superheat and subcooling targets, testing capacitors and contactors under load, measuring motor amp draw, clearing and treating the condensate drain, verifying temperature split across the coil, inspecting electrical connections, and confirming thermostat calibration and airflow.
That is where weak capacitors get caught before they strand you, where a developing leak shows up as a charge discrepancy, and where a coil gets cleaned before it costs you capacity in August. Spring is the right time. If it is already hot and you have not had it done, do it anyway.
See our air conditioning service, repair, and installation
What to do while you wait for service
- 01
Check the simple things first
Thermostat set to cool and below room temperature, fresh batteries, the breaker for both indoor and outdoor units, and the filter. A badly clogged filter causes most no-cooling calls we get.
- 02
If the coil is frozen, shut cooling off and run the fan
Set the thermostat to off for cooling and the fan to on. That thaws the ice over several hours. Never chip at it. Then leave it off until someone looks at the cause.
- 03
Do not keep resetting a tripped breaker
One reset is reasonable. Repeated resets feed high current into a failing component and can turn a small repair into a compressor replacement.
- 04
Protect the house while you wait
Close blinds on the sun side, avoid oven and dryer use during peak heat, run bath and kitchen exhaust fans, and move to the lowest floor. Check on elderly neighbors, because indoor heat is a genuine health risk.
No cooling during a valley heat wave counts as an emergency with us, and those calls get prioritized. A real person answers the phone around the clock. Call (509) 888-3389 or request service online, and if a repair makes more sense than a replacement we will tell you that too.