AC Keeps Shutting Off? 7 Reasons Air Conditioners and Heat Pumps Short-Cycle—and How to Fix It

Short-Cycling: Your HVAC’s SOS Flare

If your outdoor unit clicks on, hums for a minute, then quits faster than a toddler’s attention span, you’re short-cycling. It destroys efficiency, spikes your electric bill, and can toast a compressor faster than you can spell “replacement quote.”

The Seven Usual Suspects

1 | Oversized System – Yep, Size Matters

If you or the former homeowner installed a larger unit than should be designed for the home because “bigger = better”,  the reality is oversized units satisfy the thermostat before humidity drops, so they ping-pong on the relay all day. This creates lots of shutting on and off for your outdoor unit, and can short out the compressor prematurely.

2 | Dirty Air Filter – The Repeat Offender

A clogged MERV 13 turns airflow into a trickle. Low evaporator temperature trips the low-pressure switch and the unit shuts off to avoid freezing up.

3 | Thermostat Gone Rogue

Loose wire, dying batteries, or it’s basking in direct sunlight like a lizard—any thermostat can fake a false “target temp reached” signal.

4 | Low Refrigerant Charge

A leaking system equates to a drop in refrigerant pressures. The system hits its low-pressure cutoff, resets, restarts, repeat. (Also means you’re venting $$$ coolant.)

5 | Iced Evaporator Coil

Moist air + low temp = ice blanket. This means the unit is strangled and will short cycle..

6 | Restrictive Ductwork

Crushed flex duct or 1950s undersized returns starve airflow causing, you guessed it, the coil to freeze and the unit to short-cycle.

7 | Failing Capacitor

When the capacitor weakens, the motor can struggle to hit its rotations per minute and overload/overheat. When the motor cools down, it will try to start up again in a viscous cycle. This can lead to premature wear on your compressor.

DIY Triage vs. “Phone Now” Red Flags

DIY Check

How-To

Call-Dad Threshold

Swap filter

Obvious, but do it first

Still cycles?

Thermostat batteries/settings

Replace, relocate, recalibrate

Screen blank / temp jumps

Visual refrigerant oil stains

Just look!

Any oily residue = leak hunt

Energy Math: How Short-Cycling Prints Money for Your Utility Company

Startup amps = 5-8× run amps. Ten extra cycles/hour can inflate the bill 20+ %. Over a Carolina summer, that’s a weekend at the beach—gone.

If the breaker looks like it’s doing CrossFit, Call Dad before your compressor files a workers’ comp claim. We’re on the way-’cause that’s what Dad would say!

‍