AC Troubleshooting Guide for Central Texas Homes
This guide organizes cooling problems by what you observe, then explains the usual suspects behind each one and the point where homeowner checks stop and professional diagnosis begins.
Nothing here is a remote diagnosis. Confirmation always comes from measurements at the equipment.
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Nothing runs at all
- Check thermostat mode, setpoint and batteries.
- Check the breakers and the indoor service switch; reset once only.
- A tripped condensate float switch is a very common cause of a totally dead system.
- Beyond that: control transformer, low-voltage fuse, contactor or wiring — professional territory.
Indoor blower runs, outdoor unit does not
- Check the outdoor breaker and disconnect.
- Listen for a hum or click at the outdoor unit and report what you hear.
- Likely candidates: capacitor, contactor, condenser fan motor, compressor.
- Do not remove the electrical panel cover on the outdoor unit.
Both units run, house stays warm
- Compare airflow and temperature at the vents: weak-but-cool versus strong-but-warm.
- Replace a dirty filter and open blocked registers.
- Clear debris and vegetation from around the condenser.
- Likely candidates: dirty coils, refrigerant charge or leak, compressor performance, duct leakage.
Ice on the coil or lines
- Turn cooling off, set fan to on, and let it thaw fully.
- Replace the filter; check for closed registers.
- Likely candidates: airflow restriction, dirty coil, blower problem, low charge.
- Do not chip ice or apply heat.
Water around the indoor unit
- Turn the system off if water is near electrical parts or a finished ceiling.
- Check whether a float switch shut the system down.
- Likely candidates: clogged drain, pan problem, thawing coil, failed condensate pump.
Unusual sounds
- Buzzing or humming at startup: capacitor, contactor or a compressor struggling to start.
- Grinding or squealing indoors: blower motor or wheel.
- Rattling outdoors: loose panel, fan blade or debris.
- Clicking that repeats: control or relay issue.
- Persistent hissing: possible refrigerant leak — leave it alone and have it checked.
Short cycling
- Note how long the system runs before shutting off.
- Check filter and register restrictions.
- Check whether the thermostat is in sun, near a lamp or above a register.
- Likely candidates: control issues, airflow, refrigerant, protective devices, oversizing.
Uneven room temperatures
- Note which rooms and what time of day.
- Open all supply registers and clear returns.
- Likely candidates: duct sizing and leakage, attic heat gain, return air capacity, blower speed, zoning issues.
Where homeowner troubleshooting ends
Settings, filters, vents, visible ice or water, and breaker status are all fair game. Everything past that — electrical testing, capacitor handling, refrigerant work, opening sealed or high-voltage equipment — belongs to someone with the tools and training to do it safely.
Frequently asked questions
What is the single most common cause of no cooling?
Across a summer, restricted airflow from a neglected filter and failed electrical start components such as capacitors account for a large share of no-cool calls.
Can I diagnose refrigerant level myself?
No. It requires gauges, temperature measurements and training, and refrigerant should not be handled by homeowners.
Is it safe to run the fan with cooling off?
Generally yes, and it is specifically helpful for thawing a frozen coil. Stop if you see water spreading or smell anything burning.
How do I describe my problem clearly on the phone?
Say what runs and what does not, what the air at the vents feels like, the indoor temperature versus setpoint, and whether there is ice, water, smell or noise.
AC Not Cooling in Killeen?
Call any time, day or night, to talk through what your air conditioner is doing and request service.