Superheat Calculator

AC Troubleshooting

AC not blowing cold air? Check it against your maker's own manual

Answer what you can see, hear and smell at the unit. The stop conditions come first, then what your unit's maker prints about normal delays and the checks it gives the owner, each quoted with its document where one is held here. If you can measure the air at a return grille and a supply register, the page looks up the target split for your conditions. Nothing here asks you to open the unit. The documents behind these checks are listed in the source receipt below.

Questions

Should I turn my AC off if it's not cooling?

It depends on what you see, hear or smell at the unit. For a burning or electrical smell, a breaker that trips again after it was reset, or the outdoor unit humming while its fan stays still, this page says to stop using the system and call a technician. For ice or frost on the copper lines or the indoor unit, every maker web page quoted here says to turn the system off, and some also say to run the indoor fan while it thaws; each page is quoted. The check on this page asks about each of these first.

How long should I wait for my AC to start again?

There is no one figure. The owner documents quoted on this page print these: Carrier (Catalog No. OG-ACR454GEN-02, Edition Date 01/24): "Time delays - depending on the air conditioner you have, there may be delays in unit operation that are built-in to protect the equipment and your comfort. Don't be alarmed if you notice a time delay in operation. It may be a standard protection feature of your equipment." York (1183508-UUM-O-0121 (2021)): "Eliminate problem, turn off the thermostat for 10 s and attempt start. Wait 5 min. If system does not start, call your servicing dealer." Goodman (P/N IO-258W, July 2021): "Wait 15 minutes. Some devices in the outdoor unit or in programmable thermostats will prevent compressor operation for awhile, and then reset automatically. Also, some power companies will install devices which shut off air conditioners for several minutes on hot days. If you wait several minutes, the unit may begin operation on its own." Pick your brand on this page to see only your maker's words.

What temperature split should my AC have?

There is no single number. CEC Joint Appendix JA6, Table JA6.1-1 (2019 and 2022 editions; JA6.1 is RESERVED in the 2025 edition) gives a target that depends on the return air's dry-bulb and its wet-bulb, and its minimum airflow criterion fails only when the measured split is more than 5°F above that target, after at least 15 minutes of cooling with the outdoor air at 65°F or warmer. The procedure covers ducted split systems in cooling. Enter the readings on this page and it looks the target up for your conditions.

Why doesn't this page tell me the most likely cause?

This page does not say which cause is most likely. A ranking here would be our own guess, so it quotes what the unit's maker prints where its document is held here, and leaves the order out.

Look up the unit's age and warranty linesSuperheat and subcooling, for gauge readings