What to Check Before You Call an HVAC Tech

Sometimes the system quits and there is nothing you can do about it until somebody with gauges and a meter shows up. But a fair number of the calls we drive out to in Hickory and around the foothills turn out to be one of five things a homeowner could have checked in about ten minutes.

We would rather tell you that up front than charge you to flip a switch. So here is the short list, in the order we would work it ourselves, and the point where you should stop and call somebody.

The thermostat is set the way you think it is

Walk over and look at it. Not from the hallway. At it.

Is it set to HEAT or COOL, and not to AUTO or OFF? Is the setpoint actually above or below the room temperature — if the house reads 74 and the thermostat is set to 74, the system has no reason to run. Is the fan switch on AUTO rather than ON? A fan stuck on ON runs constantly and blows room-temperature air between cycles, which feels exactly like a system that has stopped working.

If the screen is blank or dim, change the batteries. Most wall thermostats take two AAs behind a faceplate cover that pops off by hand. That is the only part of a thermostat you should be opening. The wiring behind it is live, and shorting it can take out a control board that costs far more than the service call you were trying to avoid.

The filter is not choked

This is the single most common cause of “it runs but the house never gets comfortable.”

Pull the filter out and hold it up to a light. If you cannot see light through it, it is finished. A clogged filter starves the blower, which drops airflow, which makes the system run longer and longer for less and less result. In cooling it can freeze the indoor coil solid. In heating it can trip the system off on a high-limit switch.

Put a clean one in facing the right direction — there is an arrow on the cardboard edge, and it points toward the furnace or air handler, in the direction the air travels. Then write the date on the edge with a marker so you are not guessing in three months.

Something has power that should not be off

Check three things, in this order.

The breaker panel: look for a breaker sitting halfway between ON and OFF. To reset it, push it all the way to OFF first, then firmly back to ON. If it trips again, stop. A breaker that trips twice is telling you something real, and the next step is a meter, not another reset.

The switch on the wall next to the indoor unit: it looks exactly like a light switch and it is very easy to knock off. In an attic or a crawlspace, it may have been switched off by whoever was up there last.

The disconnect box outside next to the condenser: a small gray box on the wall with a pull-out handle. Make sure the handle is seated all the way in. Do not open the box or pull anything else out of it.

The outdoor unit can breathe

Go outside and look at the condenser. Grass clippings, leaves, mulch and weeds pack into those fins over a season, and the unit cannot dump heat through them.

Clear everything back about two feet on all sides and pull off anything sitting against the coil. Do that with the system off at the thermostat.

Rinsing the outside of the fins gently with a garden hose is fine. Do not open the top of the unit, do not remove the electrical panel on its side, and do not go after the fins with a pressure washer. The cabinet holds a capacitor that stores a charge even with the power off, and the fins bend if you look at them wrong.

The condensate drain is not backed up

Air conditioning pulls water out of the air, and that water has to go somewhere. When the drain line clogs, usually with algae, the water backs up, and most systems have a safety switch that shuts everything down rather than let it overflow into your ceiling.

The tell is a system that will not start at all on a hot day with no other symptom, or water standing in the pan under the indoor unit. If you find standing water, you have found your problem, and it is worth a call.

Stop and call us when you see any of this

Some things are not troubleshooting. They are reasons to stop.

You smell gas. Do not touch a switch, a thermostat or a phone inside the house. Get everyone outside, then call your gas utility from outdoors. Call us after they have cleared it.

You smell something burning, or hot plastic. Shut the system off at the thermostat and at the breaker.

The breaker trips more than once. That is a fault, not a nuisance.

There is ice on the refrigerant lines or the indoor coil. Turn the system to OFF and the fan to ON, and let it thaw completely before anything else. Ice usually means low airflow or low refrigerant, and both need a technician.

The system is short cycling — starting and stopping every few minutes rather than running a full cycle.

Anything that involves opening a panel, touching a wire, or handling refrigerant. Refrigerant work requires EPA certification, and the electrical side is the part that hurts people.

What we do when we get there

We run the same diagnostic process on every call, because guessing is how you end up back at the same house twice. We check the thermostat and the call for heat or cool, then airflow, then the electrical side, then refrigerant pressures and temperatures if it is a cooling or heat pump issue.

Then we tell you what we found, what it needs, and what can wait. If a fifteen-year-old system needs a part that is worth putting in it, we will say so. If it does not, we will say that too. A two-year-old system does not need everything a fifteen-year-old system needs, and we are not going to pretend otherwise to write a bigger ticket.

If you have run the list and it still will not run

Call or text us at (828) 308-0928 and tell us what you already checked. That genuinely saves time — if we know the filter is new and the breaker is holding, we start further down the list.

Southern Summit HVAC is a veteran-owned, residential heating and cooling company working out of Hickory and covering Burke, Catawba, Caldwell, McDowell and Rutherford counties. NC License #33148.