Heat pump blowing cold air in heating mode
Before you worry: a heat pump that blows cool for a few minutes now and then is often doing exactly what it should — melting frost off the outdoor coil.
tuneWhat are you noticing?
Select anything that matches and the checklist below reorders to fit. Not sure? Skip it.
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Start here
In Canadian winters, watch the timing first. If the cool air lasts only a few minutes and warm heat returns on its own — often with a whoosh and some steam off the outdoor unit — that's a normal defrost cycle, not a breakdown. Note how long it truly stays cold before assuming a fault.
Ranked from real-world failure data. The order updates as you select what you’re noticing above.
Likely causes, in the order to check them
Showing the typical order Beginner-friendly Doable, with care Safety-critical Call a pro
handymanHow to fix it
Find the filter at the indoor air handler or return grille, note the size printed on its frame, and slide in a fresh one facing the airflow arrow the right way.
- Locate the filter slot on the indoor air handler or the large return-air grille.
- Slide out the old filter and read the size stamped on its cardboard frame.
- Insert a matching new filter with the printed airflow arrow pointing toward the unit, and set a reminder to check it monthly in heating season.
schedule10 min savings$8–20
gavel Check your province first AB: homeowner may do this · BC: homeowner may do this · ON: homeowner may do this · PE: homeowner may do this · QC: homeowner may do this
Replacing a return-air filter is routine homeowner maintenance in every province.
Replacing a return-air filter is routine homeowner maintenance in every province.
verifiedWhy this one goes to a pro
The reversing valve and refrigerant charge are part of the sealed system. In Canada, working with refrigerant requires certification, and valve replacement means brazing on pressurized lines. This is a licensed HVAC repair — a technician can confirm it quickly.
Your notes travel with the request — what you saw, what you ruled out, when it started — so the pro arrives with a head start instead of a mystery.
visibilityHow to check
warning Clear snow, but never chip the iceThe outdoor coil is thin aluminum wrapped around pressurized refrigerant tubing. Brushing snow away is fine; chipping, prying, or hammering ice off the coil can puncture it and turn a nuisance into an expensive sealed-system repair. If ice won't clear on its own, let a technician handle it.
- Go outside and look at the whole outdoor unit — light frost is normal in winter, but a solid coat of ice over the coil or snow drifted against the sides is not.
- Clear snow away from the sides and top by hand or with a soft brush so air can move through the coil.
- Let the unit run through a defrost cycle. If it clears and stays clear, you're done; if it glazes over again quickly, the defrost controls need a technician.
buildNo tools schedule10 min
verifiedWhy this one goes to a pro
The reversing valve and refrigerant charge are part of the sealed system. In Canada, working with refrigerant requires certification, and valve replacement means brazing on pressurized lines. This is a licensed HVAC repair — a technician can confirm it quickly.
Your notes travel with the request — what you saw, what you ruled out, when it started — so the pro arrives with a head start instead of a mystery.
Why the list is in this order
We don’t sort by likelihood alone. We sort the way a good, honest tradesperson thinks: rule out the free, safe, common causes first. That’s why the cheap checks outrank the expensive repairs — and why anything dangerous gets a hard stop instead of a pep talk. The order exists to save you money, not to sell you anything.