Direct answer: If an HRV or ERV is not working, the most common homeowner-level causes are lost power, a wall control setting issue, dirty HRV / ERV filters, or a unit that is in defrost or protection mode rather than fully failed.
Most likely: Start by confirming the unit has power, the wall control is actually calling for ventilation, and the HRV / ERV filters and exterior hoods are not badly blocked.
HRVs and ERVs can fail in a few lookalike ways: completely dead, powered but no airflow, intermittent operation, or airflow at some grilles but not others. Separate those patterns first. Safe checks are mostly visual and basic reset steps. If the unit has burning smells, water near wiring, damaged insulation, or you would need to open electrical compartments beyond a simple access panel, stop and move to professional service.
Don’t start with: Do not start by ordering a motor or control board. Those are higher-fitment, higher-cost parts, and many 'dead unit' complaints turn out to be a tripped breaker, disabled control, clogged filter, or frozen airflow path.
No fan sound, no indicator lights, and no response when you change the wall control or unit setting.
Start here: Start with power to the unit: breaker, disconnect or service switch, plug, and any resettable GFCI or nearby receptacle issue.
Lights or controls seem normal, but supply and exhaust airflow are very weak or absent.
Start here: Start with filters, the recovery core seating, and blocked exterior hoods or screens.
The unit starts and stops unpredictably, or seems to run only in certain weather or modes.
Start here: Check whether it is in standby, humidity control, timer mode, or defrost rather than failing outright.
The unit seems to run, but one area has little or no ventilation.
Start here: Look for a local duct issue, closed balancing damper, crushed flex duct, or blocked grille rather than a failed whole unit.
An HRV or ERV may appear dead if the breaker tripped, the plug is loose, a service switch is off, or the wall control is set to standby or an inactive schedule.
Quick check: Confirm the unit has power at its normal indicator or fan sound, then set the control to a clear continuous ventilation mode for a few minutes.
Restricted airflow can make the unit seem weak, noisy, or nonfunctional even though the fans still run.
Quick check: Remove and inspect the filters, and check the outside intake and exhaust hoods for lint, leaves, snow, or insect screen blockage.
If the core is not seated properly after cleaning, or if frost and drainage problems develop, airflow can drop sharply and the unit may cycle oddly.
Quick check: With power off, inspect whether the HRV / ERV core is fully seated, clean enough to pass air, and not frozen into place.
If power is present, settings are correct, airflow paths are clear, and the unit still will not run or only hums, the fault may be inside the unit.
Quick check: Listen for humming, repeated clicking, or one fan failing while the other does not. That points away from simple filter blockage and toward service.
Many ventilation units are left in standby, timer, humidity-only, or intermittent mode, which can look like a failure.
If it works: The unit was likely not failed; it was in standby, scheduled operation, or another control mode.
If it doesn’t: Move to power checks next so you can separate a control issue from a dead unit.
What that means: A unit that responds to a mode change usually has basic power and at least partial control function.
A tripped breaker, switched-off service disconnect, loose plug, or dead receptacle is a common reason the unit appears completely dead.
If it works: The problem was likely upstream power loss rather than a failed HRV / ERV component.
If it doesn’t: If power seems present but the unit stays dead, continue with safe access-panel checks only.
What that means: A breaker that trips again quickly suggests an electrical fault and is not a parts-buying situation for homeowners.
Filters and exterior hood blockages are the most common airflow-related causes and are often safe to address without repair work.
If it works: Restricted airflow was likely the main issue, and the unit may not need any repair part.
If it doesn’t: Continue to the core and internal airflow checks.
What that means: A unit that runs better after filter and hood cleaning usually had an airflow restriction, not a failed motor or board.
A mis-seated core, frozen core, or drainage problem can make the unit seem dead or severely weak even when the fans are trying to run.
If it works: The issue was likely airflow blockage, frost, or an installation/seating problem rather than an electrical failure.
If it doesn’t: If the unit still does not run or airflow is still missing, the remaining branches are more likely internal electrical or mechanical faults.
What that means: A clean, properly seated core with clear ducts narrows the problem toward controls, fan operation, or a less visible duct issue.
Once power, settings, filters, hoods, and core condition are checked, you can avoid guessing and buying the wrong part.
If it works: You have likely resolved a maintenance or setup issue and avoided unnecessary parts replacement.
If it doesn’t: Professional diagnosis is the safer next step because the likely causes are now internal and higher-risk.
What that means: At this point, filters are the only realistic homeowner purchase recommendation supported by diagnosis. Motors and controls remain fitment-sensitive and service-oriented.
Only use these links after your checks point to the part that actually failed.
Buy only if your existing HRV / ERV filter is disposable, damaged, misshapen, or remains clogged after the correct cleaning method for your unit.
The unit may have its own tripped breaker, service switch, unplugged cord, or wall control set to standby or intermittent mode. Confirm those first before assuming an internal failure.
Yes. Heavily loaded HRV / ERV filters can reduce airflow enough that the unit seems weak or nonfunctional, especially if the exterior hoods are also restricted.
Sometimes. Many units enter defrost or protection cycles in cold weather, which can look like intermittent failure. If it always returns to normal operation, that is different from a unit that stays dead or has no airflow.
Not based on humming alone. Humming can also happen with blocked airflow, a stuck fan wheel, or another internal electrical issue. Once you have confirmed power, settings, filters, hoods, and core condition, a humming unit is usually a service call rather than a guess-and-buy repair.
Usually only the HRV / ERV filter, and only after you confirm the existing filter is the problem and you know the correct replacement type. Motors, controls, and other internal parts are fitment-sensitive and better handled after diagnosis.