INDIANAPOLIS GUIDE

When the air conditioner will not cool

The upstairs hall is the room that gives it away. In July the air feels thick, the thermostat says the system is running, and a supply vent blows something that is not really cold. Indianapolis summers are hot and humid, so a house can feel wrong even when the equipment is only partly failing. The outdoor unit may be humming on its pad, or it may be silent while the indoor blower keeps moving clammy air. Start with what you can see: the filter, the return, and whether the copper line is sweating or wearing a sleeve of ice.

By Mike Maziarz · Sources checked October 6, 2026 · How we write these guides

Humidity is part of the symptom

Cooling in this climate is not only a temperature job. The coil is supposed to pull moisture out of the air as it cools. If the system runs and the house stays clammy, write that down separately from the thermostat number. A room at the setpoint that still feels wet is a different note from a room that climbs all afternoon.

Check a supply vent and a return. Supply air should feel distinctly cooler than the air going back into the return. If you cannot tell them apart, say so. Do not stick a thermometer into the duct if it means taking a panel off. Your hand and a sentence are enough for the first call.

Outdoor air quality and a stagnant, hazy day are not the same problem as a failed compressor, though both can make a closed house feel heavy. If smoke or ozone is in the forecast, keep windows shut and still describe what the equipment is doing. Weather and the machine can be true at the same time.

Ice on the line or the coil

A frozen suction line, the larger insulated pipe at the outdoor unit or at the indoor coil, means the system has been running without enough heat transfer. Turn the cooling off. Leave the blower on only if the thermostat has a fan setting that runs air without the compressor, and only if continuing to run it does not make a grinding or squealing noise. Let the ice melt on its own. Do not chip it, and do not pour hot water through the cabinet.

While it thaws, look at the filter and the returns. A starved coil freezes. So can a coil that is low on refrigerant, and you cannot tell those apart from the hallway. Write whether the ice was on the indoor cabinet, the outdoor line, or both, and how long the system had been running.

After the ice is gone, do not immediately set the thermostat far down to catch up. Run a normal cycle and see whether ice returns. If it does, shut cooling off again and call. Repeating the freeze is how a coil gets damaged. It is also a reason to talk about repair versus a deeper failure, which the repair or replace page frames without dollar figures.

The filter and the hall return

The return is often a grille in the hallway, sometimes one upstairs and one down. If furniture, a rug, or a closed door blocks it, the system cannot move air. In a basement house the filter may be at the furnace. In a closet or attic air handler it may be behind a narrow panel in the hall. Find it before you assume the outdoor unit is the whole story.

If the filter is gray and bowed, replace it with the size printed on the old frame or on the slot. Write the date on the new frame. A filter you changed yesterday is still worth mentioning, because a wrong size that bends out of its track pulls unfiltered air and can still starve the coil.

Do not run the system with the filter removed as a test for more than a moment of observation, and do not leave it that way. The filter is there for the coil as much as for the rooms. If airflow is still weak with a clean filter and open returns, that belongs in the notes as a duct or blower clue, not as a reason to keep the filter out.

What the outdoor unit should be doing

On a cooling call the outdoor fan should turn and the compressor should be running, not just clicking. A click every few minutes with no fan is a finding. A fan that turns while the air inside stays warm is a different finding. Write which one you have, and whether the top of the unit is hot.

Clear debris you can lift without tools: leaves on the top, grass piled against the fins, a cover that was never taken off in spring. Stay off the electrical compartment. Do not push sticks through the fins, and do not spray a pressure washer at the coil. Bent fins block air as surely as a dirty filter.

Give the unit the space the manual asks for, which is a practical way of saying shrubs should not be touching the cabinet. If the pad has sunk and the cabinet leans, say so. You are describing the scene. You are not leveling it with a pry bar.

Do not add refrigerant

Cans of refrigerant at a parts counter are not a homeowner fix. Adding refrigerant to a system that is not repaired, or adding the wrong substance, is illegal for a reason and it can wreck the compressor. Federal rules for this work sit with certified technicians. The refrigerant guide explains the limit in plain language, including why a top-off without a leak repair is not a plan.

If a technician says the system is low, ask what they found: a leak location, a repair, and a test after the charge. You do not need the gauge numbers. You need to know whether refrigerant left the system and whether the leak was addressed. A house that cools for a week and then fades is a clue to write down.

Never jump out a low-pressure switch to force the outdoor unit to run. That switch is there because running without a proper charge destroys the compressor. If someone suggests bypassing it, stop the visit and ask for the finding in writing.

Notes that make the cooling call specific

Record the thermostat mode, the setpoint, and the indoor temperature at two times of day, morning and late afternoon. Marion County humidity makes a single glance easy to misread. If some rooms cool and others do not, name the rooms. An upstairs that never catches up is a different visit from a whole house that will not cool at all.

Say whether this is an air conditioner or a heat pump. Both can have an outdoor unit that looks the same from the yard. A heat pump that will not cool may still heat, or it may not. The heat pump page covers defrost and emergency heat so you do not describe a winter behavior as if it were a July failure.

If the thermostat clicks, goes blank, or never sends a call, start there before you condemn the outdoor unit. The thermostat guide is the short list of what a homeowner can check on the wall without opening the furnace. Bring the filter size and the outdoor unit model number to the call so the visit starts with your equipment.