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Smell gas? Leave now, then call 911 or your gas utility from outside. CO alarm sounding? Get everyone out and call 911.Gas smell or CO alarm? Get out, then call 911.

Symptoms

Six folders, by what you notice

Sounds4
Smells3
Leaks and ice3
Won't run right5
Lights, alarms and codes4
Comfort and bills3

Terms and Limits

Hum Drip Hiss gives general information about heating and cooling symptoms; it is not a diagnosis, and a licensed technician who sees your equipment decides what is wrong and how to fix it.

Updated

General information only

Every page on Hum Drip Hiss describes what a symptom usually means across many homes and many makes of equipment. Your furnace, air conditioner or heat pump may differ: blink codes, alarm patterns and safety features vary by brand and model, so your equipment's label and owner's manual come first.

Nothing here is a diagnosis, an inspection or a repair instruction for your specific system. Hum Drip Hiss is not an HVAC contractor and does no installs, repairs or visits.

Safety comes first

If you smell gas, get everyone out of the house without touching switches, phones or anything that could spark, and phone 911 or the gas company's emergency number only after you are out and at a safe distance. If a carbon monoxide alarm sounds, or people feel headache, dizziness, nausea or confusion, get everyone into fresh air and call 911 from outside. Don't go back in until responders say it is safe.

The safe checks on this site stop at the equipment cabinet. Never open refrigerant lines, burner compartments or service panels, handle capacitors, or bypass a safety switch. The stop-and-call signs list when to put the checks down and call.

Pages link to makers' manuals, government agencies, gas utilities and, on some pages, businesses that share owners with this site, as explained on the ownership and links page. Hum Drip Hiss does not control those sites, and their content, prices and policies are their own.

Liability

You use the information on this site at your own risk. Hum Drip Hiss makes every effort to keep pages accurate and to re-check them when a maker or agency changes its advice, but it cannot promise that every page fits every home or is free of error, and it is not responsible for damage, injury or cost arising from use of the information.

A licensed technician and your local building code decide what work is needed and how it must be done. When in doubt, stop and call one.