Carrier AC Not Cooling? Common Causes & How to Fix It

First, the fast checks

If your Carrier AC is running but not cooling, start with the five things that fix most no-cool calls before you pay for a visit:

1. Thermostat - set to COOL, target a few degrees below the room, fresh batteries. On a Carrier Infinity communicating thermostat, a blank or frozen screen often points to a control issue (more below).
2. Air filter - a clogged filter chokes airflow and can freeze the coil. If you can't see light through it, replace it. Here's how.
3. Breakers - check both the indoor (furnace/air handler) and outdoor AC breakers. Reset once; if it trips again, stop and call a pro.
4. Outdoor unit - is the fan spinning? Clear leaves and debris, and make sure the disconnect by the unit is in.
5. Frozen coil - ice on the refrigerant lines or indoor coil means shut the AC off (fan ON) for a few hours to thaw, then run again with a clean filter.

If it's iced up or still not cooling after these, here's what's likely going on.

The Carrier-specific causes we see most

• Infinity communicating control-board faults. Carrier's variable-speed Infinity systems run on a communicating bus, and board or communication errors are the most Carrier-specific no-cool cause - and the one most likely to stump a tech who doesn't know the platform.
• Failed run capacitor or contactor. The single most common no-cool cause on any AC. If the outdoor fan hums but won't spin (or won't start), this cheap part is the usual culprit.
• Low refrigerant from a leak. Carrier systems don't "use up" refrigerant - if it's low, there's a leak. You'll often see ice on the lines and weak airflow.
• Variable-speed (ECM) blower motor issues on Infinity air handlers - weak or no indoor airflow.

See the full list on our Carrier repair page, and our general guide to why an AC stops cooling covers the non-brand causes in depth.

When to call a pro

Call a licensed tech if: the coil keeps freezing after a filter change, the outdoor fan won't run, you suspect a refrigerant leak, the breaker trips repeatedly, or an Infinity board is throwing errors. These need gauges, parts, and a tech who knows Carrier.

Wondering if it's even worth fixing? Our Carrier brand review covers reliability and repair-vs-replace.

Carrier AC down today? Get matched with a licensed local pro for same-day Carrier repair - upfront pricing, no overtime fees.