Troubleshooting
Step-by-step diagnosis for the most common cooling and heating faults, ordered from the cheapest check to the one that needs a technician.
Calculators
AC Compressor Replacement Cost: Typical Prices and Repair vs ReplaceReplacing a residential AC compressor typically costs about $1,500–$4,500 in the US out of warranty, and roughly $1,000–…AC Vent Temperature: Check Your Temperature Split (Calculator)Subtract the supply-register temperature from the return-grille temperature. A healthy central AC usually shows a split …
Guides
AC Breaker Keeps Tripping: Causes, Safe Checks and RepairsA breaker that trips repeatedly is telling you the AC is drawing more current than the circuit allows, or that there is …AC Drip Pan Overflowing: Why It Happens and How to Clear ItAn overflowing drip pan almost always means water is not leaving through the condensate drain fast enough, and a clogged…AC Making Noise? What Buzzing, Hissing and Banging Sounds MeanEvery AC hums, whooshes and clicks a little. New noises are worth chasing: buzzing usually points to an electrical part,…AC Not Blowing Cold Air: Causes and a Step-by-Step DiagnosisWhen the AC runs but the air is warm or only slightly cool, check the thermostat mode and fan setting, the filter, and w…AC Not Removing Humidity: Why the House Feels Cold and ClammyAn AC removes moisture only while its coil is cold and running long enough for water to drip off. Oversized equipment, a…AC Short Cycling: Why Your Air Conditioner Turns On and Off FastShort cycling means the compressor starts and stops every few minutes instead of running steady cycles of roughly 10–20 …Condensation on AC Vents: Why Registers Sweat and How to Stop ItAC vents sweat when the metal register is colder than the dew point of the air around it. Supply air is usually 55–60 °F…Cracked Heat Exchanger: Signs, Carbon Monoxide Risk and What to DoA cracked heat exchanger is a breach in the metal wall that keeps furnace combustion gases separate from the air you bre…Dehumidifier Freezing Up: Why Coils Ice Over and How to Fix ItA compressor dehumidifier freezes when its cold coil drops below 32 °F, which happens most often when the room is below …Furnace Blowing Cold Air? Causes and Step-by-Step FixesMost often the thermostat fan is set to ON instead of AUTO, the filter is clogged, or the furnace has locked out after a…Outside AC Unit Not Running but Inside Fan Works: What to CheckIf the indoor blower runs but the outdoor unit stays silent, either the outdoor unit has lost power or it is not receivi…Thermostat Not Reaching Set Temperature: Causes and FixesIf your system runs and runs but the house never reaches the setpoint, the cause is either too little delivered capacity…Window AC Freezing Up: Why the Coil Ices Over and How to Fix ItA window AC freezes when its indoor coil drops below 32 °F. The usual causes are a dirty filter, running on low fan when…Window AC Leaking Water Inside? Tilt, Drain Holes and Pan FixesWindow ACs are meant to drain condensate outdoors, so water inside usually means the unit is tilted toward the room, the…