Guide
AC guide: what to do when the cooling stops
A plain-English walk-through for a desert home, from the moment the air turns warm to the day the system is working again.
The first 15 minutes
Quick checks and staying cool
Check the simple things
Thermostat on Cool and set low enough, batteries, both breakers, and the filter.
Protect people first
If the house is heating up, move babies, older adults, anyone unwell and pets somewhere cool. Call 911 for signs of heat illness.
Don't make it worse
If there is ice, switch to fan only. If a breaker trips twice, leave it off.
Call with details
Tell the contractor what the system is doing, its age if you know it, and anything that changed.
While you wait
Keeping the house cooler
- Close blinds and curtains on sunny windows, especially west-facing ones in the afternoon.
- Run ceiling fans and portable fans, and avoid the oven and dryer.
- Drink water, even if you don't feel thirsty.
- Maricopa County runs a Heat Relief Network of cooling and hydration stations each summer.
- If the house gets dangerously hot, go somewhere air-conditioned for the afternoon.
Repair or replace?
There is no single rule. Look at the age of the system, how often it has failed, what this repair costs and what the system runs on. Small electrical repairs are usually worth it on any system that is otherwise sound. Major repairs on older systems are where it makes sense to price a replacement too.
Desert systems often need replacement sooner than the same equipment in a mild climate, because of the long, hard cooling season. If you are spending on the same system every summer, ask for both prices in writing.
R-22, R-410A and what comes next
Older systems, typically installed before 2010, use R-22, which is no longer produced in or imported into the US. It is still available from recycled stock, but it is expensive, so leaks on R-22 systems get costly fast.
Most systems installed after that use R-410A. Federal rules are now phasing that down too, and new systems use lower-impact refrigerants such as R-454B or R-32. You don't need to replace a working R-410A system, but if you are buying new, ask which refrigerant it uses and why.
Look after it before summer
A spring tune-up, a clean outdoor coil, a clear condensate drain and regular filter changes prevent many of the breakdowns that happen on the hottest days. After a monsoon dust storm, check the filter and rinse dust off the outdoor coil with a garden hose, with the power off.
Choosing a contractor
Five checks before you sign
- Look up the Arizona Registrar of Contractors licence at roc.az.gov.
- Ask for proof of liability insurance.
- Get the price and the scope in writing before work starts.
- For a replacement, ask for a load calculation and whether a permit is included.
- Be wary of pressure to decide on the spot, and of anyone who quotes a new system without looking at the old one.
Questions
Common questions
What indoor temperature is too hot?
There is no single number, but heat builds up quickly in a closed house in summer and is most dangerous for babies, older adults and people with health conditions. If the house is getting hotter and can't be cooled, move vulnerable people somewhere cool.
How long should an AC run in summer?
On the hottest afternoons, a properly sized system may run almost nonstop. It should still cool the house down in the evening and cycle off overnight.
Where do I check a contractor's licence?
The Arizona Registrar of Contractors has a licence search and a complaints process.
AC not keeping up?
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