AC Running but Not Cooling? A 10-Step Troubleshooting Guide for Amarillo Homes

“It’s running but it’s not cooling” is the most common summer complaint Amarillo HVAC contractors hear, and a surprising share of those calls end with the technician changing a filter, thawing a coil, or hosing off a condenser — things you could have done yourself before paying a $75–$150 diagnostic fee. This guide walks through the checks in the order a technician would do them, tells you what each symptom usually means and what it costs to fix in Amarillo, and marks the points where you should stop and call a licensed pro rather than keep poking.

Cost figures here match the Amarillo AC repair cost guide. If the house is already dangerously hot, skip to the emergency guide first.

Before you start: two Amarillo-specific realities

Dust. The Panhandle’s spring winds load air filters and condenser coils with dirt faster than almost anywhere in Texas. A filter that lasted three months last winter can be choked in five weeks in April and May. Half the airflow problems below trace back to this.

Hail. Amarillo has a primary hail season from March to early May and a smaller one in September–October. If your cooling problem started after a storm, look at the outdoor unit before you do anything else — flattened fins or a bent fan blade change the whole diagnosis. The hail-damage guide has a five-tier scale for that.

The 10-step check

Work in order. Each step is either free or nearly free. “STOP” means stop troubleshooting and call a licensed technician.

1. Thermostat

Mode on COOL, fan on AUTO (not ON — ON runs the blower continuously and can make the air feel warm between cycles), set point at least three degrees below the room reading. If the display is dim or blank, change the batteries. Check for a schedule or vacation hold overriding your setting. This resolves more “no cooling” calls than anyone likes to admit.

2. Air filter

Pull it. Hold it up to a light. If you can’t see through it, replace it. Use the same size and a moderate MERV rating (8–11 is the usual residential range; very high-MERV filters restrict airflow on systems not designed for them). A starved system can’t move enough air across the indoor coil, and the coil freezes — which brings us to step 4.

3. Registers and return

Open every supply register, including in rooms you don’t use — closing them doesn’t save energy on most systems and does raise pressure and reduce airflow. Make sure the big return grille isn’t behind a bookcase or covered by a rug.

4. Ice

Look at the indoor coil (behind the access panel on the air handler, if you can reach it safely) and at the larger copper line where it enters the outdoor unit. Frost or ice means the coil is too cold, which happens for one of two reasons: not enough warm air moving across it (filter, blower, blocked returns) or not enough refrigerant in it (a leak).

Set the thermostat to OFF and the fan to ON. Wait two to three hours. Replace the filter in the meantime. Then turn cooling back on. If it runs normally, you had an airflow problem and you fixed it. If it freezes again with a clean filter, STOP — it’s almost certainly low refrigerant, which means a leak, which is a $400–$1,600 repair and not a DIY job. Don’t chip at the ice and don’t run the compressor while it’s frozen.

5. Breakers and disconnect

At the electrical panel, look for tripped breakers — there are usually two, one for the outdoor condenser and one for the indoor air handler. Reset once. If either trips again, STOP and leave it off; repeated tripping means a real electrical fault or a compressor that’s locking up. Outside, check that the disconnect box on the wall near the condenser hasn’t been switched off or had its pull-out removed (kids, lawn crews, and the last technician have all done this).

6. Watch the outdoor unit start

Have someone set the thermostat to call for cooling while you stand by the condenser. Within a minute or two the fan should start spinning and you should hear the compressor come on with a deeper hum.

• Fan spins, compressor hums along: the unit is running; move to step 7.
• Humming or buzzing, fan not spinning: classic failed capacitor. STOP. It’s a $150–$400 repair in Amarillo, and letting it keep trying to start is hard on the compressor. You can sometimes nudge the fan with a stick to get it going — don’t; it’s a one-time trick that ruins the motor.
• Nothing at all, no hum: could be the contactor, the disconnect, a low-voltage wire, or the thermostat. STOP and call.
• Rhythmic ticking or wobbling: likely a bent fan blade, common after hail. STOP — a blade is cheap, a motor is $300–$700, and running it out of balance turns the first into the second.

7. Outdoor coil: dirt and hail

Look at the fins on all four sides. In Amarillo they’re usually coated with a film of dust, sometimes cottonwood fluff in early summer, sometimes grass clippings from the last mowing. Flattened fins in a splatter pattern mean hail. Both restrict the coil’s ability to dump heat, which makes the system run hot and cool poorly.

Turn the power off at the disconnect. Clear debris by hand. Rinse the coil gently with a garden hose, spraying from the inside out if you can get the top off safely (or just from the outside at low pressure if you can’t). Never use a pressure washer — it flattens fins. Let it dry, restore power, and test. A coil wash alone can restore several degrees of cooling.

Bent fins need a fin comb, which is inexpensive but tedious; most homeowners leave that to the technician. If the fin damage is extensive or the coil is leaking (oily residue on the fins is a tell), see the hail-damage guide.

8. Condensate drain

Cooling produces water — a lot of it on a humid day, less in Amarillo’s dry heat, but enough to clog a drain line with algae over a season. Many air handlers have a float switch in the drain pan that shuts the whole system off when the pan fills, to protect your ceiling. Look for standing water around the indoor unit or in a secondary pan under an attic air handler. Clearing the line is usually simple (a wet/dry vac at the outdoor drain outlet does it), but if you’re not comfortable, STOP and call — it’s a quick, inexpensive service call.

9. Temperature split

After the system has run for 15 minutes, hold a thermometer in the air coming out of a supply register, then in the air going into the return. A healthy system delivers supply air roughly 15–20°F cooler than the return. A split under about 10°F, after you’ve done steps 1–8, points to low refrigerant, a weak compressor, or a metering problem — STOP and call. A split over 22°F or so usually means restricted airflow (back to steps 2–4).

10. Give it time — within reason

On a triple-digit afternoon, a correctly sized Amarillo system may pull the house down only a degree or two per hour and may not reach 72°F until after the sun leaves the west side of the house. That’s physics, not a malfunction. What’s not normal: running continuously while the house gets warmer, or failing to hold within a few degrees of the set point once the sun’s off the wall. If that’s happening after all of the above, schedule a diagnostic.

What each finding usually costs in Amarillo

What you found	Likely cause	Typical fix	Amarillo cost
Dirty filter, no ice	Airflow	New filter	Cost of a filter
Ice, cleared with new filter	Airflow	Filter + thaw	Free
Ice returns with clean filter	Refrigerant leak	Leak repair + recharge	$400–$1,600
Outdoor unit hums, fan won’t spin	Capacitor	Capacitor replacement	$150–$400
Outdoor fan spins slowly / ticks	Fan motor or bent blade	Blade or motor	$300–$700 (motor)
Dirty coil	Heat rejection	Coil wash	Often within a $75–$150 visit
Flattened fins after hail	Hail damage	Fin comb / coil repair	$75–$700; see hail guide
Water at indoor unit, system off	Clogged drain / float switch	Drain clear	Usually within a diagnostic visit
Everything runs, split under 10°F	Refrigerant or compressor	Diagnosis required	$75–$150 to find out; compressor $1,500–$3,000 if that’s it

When it’s a bigger conversation

If the diagnosis comes back as a refrigerant leak on an R-22 system, a compressor, or a coil on a unit that’s 12 or more years old, you’re not in troubleshooting territory anymore — you’re in the repair-vs-replace decision. Ask the technician to quote both, and read that guide before you decide.

Get a licensed diagnosis

If you’ve worked through the list and hit a STOP, Palo Duro Air Repair connects Amarillo, Canyon, and Bushland homeowners with independent HVAC contractors who report holding an active Texas ACR license. Tell us what you found — “hums but fan won’t spin” or “ice comes back with a clean filter” gets you the right technician with the right parts on the truck. Verify any contractor at the TDLR license lookup before work begins. No obligation to hire.