Your nose is a good early warning system. A heat pump that suddenly smells different is usually telling you something, and a few of those smells mean you should shut it off right away. Here's what the common ones usually mean.
Shut it off and call: fishy or burning plastic
A fishy smell surprises people, but it's one of the most important to act on. Wiring insulation and plastic electrical parts often give off a fishy odor when they overheat. A burning plastic or electrical smell, or a smell like gunpowder, points the same way: a motor, a circuit board or a connection running too hot.
- Turn the system off at the thermostat.
- If the smell is strong, or you see smoke or scorch marks, turn off the breaker for the heat pump too.
- Don't turn it back on until a technician has looked at it.
Leave the house: rotten eggs
A heat pump runs on electricity, not gas. But if your home also has gas, such as a furnace, a water heater or a range, a rotten egg or sulfur smell may be natural gas, which is given that smell on purpose. Don't flip switches or use anything that could spark. Get everyone outside, then call the gas company or 911 from outside.
Usually normal: dusty burning on the first cold day
The first time the heat runs after months off, dust that settled inside the system and the ducts over the summer can give off a faint dusty smell for a short while. That should fade within an hour or so. If it doesn't, or it smells like plastic rather than dust, treat it as the burning smell above.
Musty, mildew or "dirty socks"
A musty or mildew smell usually means moisture and growth somewhere it shouldn't be: a clogged condensate drain or pan, a dirty indoor coil, or a filter that's overdue. A smell like dirty socks, often strongest when heating starts or after the system defrosts, is bacteria growing on the indoor coil. Neither is an emergency, but both get worse, and they affect the air you're breathing. Change the filter, and have the coil and drain cleaned. That's part of a maintenance visit.
Chemical or sweet
A faint chemical or sweet smell near the indoor or outdoor unit can come from a refrigerant leak. Leaking refrigerant also means the system will heat and cool poorly and can damage the compressor. Finding and repairing a leak is a job for a certified technician, so call rather than wait.
Something died: a rotting smell
A strong rotting smell that comes through the vents can mean an animal got into the ductwork or the indoor unit. It needs to be found and removed, and the area cleaned.
When to call
- Right away: fishy, burning, electrical or gunpowder smells, or any smoke
- Right away, from outside: rotten eggs (the gas company first)
- Soon: chemical or sweet smells, rotting smells, or a dusty smell that doesn't fade
- At your next tune-up, or sooner if it bothers you: musty or dirty-sock smells
Call us at 805-965-6326 or send us a message, and tell us what the smell is like and when you notice it. That helps our technician find the cause faster.
Related
More tips on heat pumps, air quality.