When an air conditioner stops working in a Leander house in September, the first five minutes belong to you, not to us. Plenty of no-cool calls in Leander, Cedar Park and Liberty Hill end at a thermostat setting, a switch or a filter, and those are things you can check before you pick up the phone. Here is the list in the order we would check it at your door, and the three signs that mean stop checking and shut the system off.
Start at the thermostat
Confirm the thermostat is set to Cool and the setpoint is below the room temperature. Carrier's own troubleshooting guide starts here for a reason: a thermostat left on Heat or Off after a cool morning, or bumped to a setpoint above the room, produces a system that looks dead and is fine. Carrier also says to check whether the fan is set to Auto, On or Off. If the screen is blank, the thermostat may simply need batteries, and a blank screen means nothing is telling the system to run.
Check the breaker, once
Go to the electrical panel and find the breaker for the air conditioner. Carrier's guidance is to verify that the breaker for the HVAC system is in the On position; a breaker in the middle position has tripped, and you reset it by pushing it fully off and then on. Do this one time. If the breaker trips immediately after resetting, Carrier says not to try again, because a breaker that will not hold is reporting an electrical fault that needs a professional, and repeated resets can turn a repair into a replacement.
Find the two switches
Two switches turn an air conditioner off without touching the breaker. Carrier notes that many systems have a power switch near the indoor air handler or furnace that looks like a light switch, and that the outdoor unit usually has a disconnect box on the wall beside it. A disconnect that has been turned off or pulled out is, in Carrier's words, a common reason an air conditioner will not turn on. Painters, roofers and pest control crews pull that disconnect and forget it.
Pull the filter and look at it
A clogged filter can stop a system cold. Carrier describes a clogged filter as a leading cause of performance issues and says to replace it if it is gray or clogged; its guide on an AC that runs but does not cool explains that a dirty filter blocks airflow, reduces cooling and can cause the system to shut down. ENERGY STAR's rule is to check the filter monthly in heavy-use months and change it at least every 3 months. A Central Texas summer counts as heavy use from May onward.
Look at the outdoor unit
The outdoor unit has to breathe. Carrier's list of reasons an air conditioner runs without cooling includes a condenser blocked by dirt, grass and debris clogging the fins, which reduces efficiency and can damage the compressor. Clear grass clippings, leaves and anything stacked against the unit, and make sure the fan on top is turning when the system calls for cooling. Do not open the cabinet and do not hose the fins from close range; clearing what is around the unit is the homeowner's job, and cleaning the coil is ours.
Running but not cooling
If the system runs and the air is not cold, the same three causes lead Carrier's list: the thermostat, the filter and the outdoor coil. Beyond those, the causes are professional ones. A frozen evaporator coil is best handled by a technician because reaching it is difficult, a refrigerant leak requires certified handling and is not something to attempt yourself, and an undersized unit will struggle to keep up as outdoor temperatures rise. A system that cools until mid-afternoon and then loses ground on the hottest days is describing one of those.
Three signs to shut it off now
Carrier draws a hard line here, and we agree with it. If you hear buzzing, smell burning, or see ice on the coils or the refrigerant lines, shut the system off and call for service immediately. Ice in particular is not a sign the unit is working extra hard; Carrier's instruction is to shut the system off at once to prevent compressor damage, because a compressor pulling liquid refrigerant is the failure that ends a system.
While you wait for the technician
A house without air conditioning in a Central Texas summer is a health matter, not only a comfort one. The CDC's guidance is to use fans only while indoor temperatures are below 90°F, because above that a fan can raise body temperature rather than lower it. It also names the people who need extra care on hot days: anyone 65 or older, infants and young children, pregnant women, and people with heart disease or asthma. If the house is past 90°F and someone in it is on that list, the CDC's advice is to find a place with air conditioning, and dialing 2-1-1 will locate one.
How we handle it
Tell us what you checked when you call. A thermostat that is blank, a breaker that will not hold, or a disconnect you found pulled each points to a different part, and it tells us what to bring. Many same-day visits end with a part replaced on the spot, and the ones that do not end with an honest conversation about whether an AC repair is the right money on that unit. Our emergency AC repair page covers how the after-hours call works.
Comfort Pros is a Carrier dealer serving Leander, Cedar Park, Georgetown and Liberty Hill, licensed under TACL# TACLB116912E. ENERGY STAR's advice is that a yearly tune-up improves efficiency and comfort; ours is that a spring maintenance visit is how most of these calls never get made.