Is the unit completely dead?
Check the breaker, nearby service switch, plug or disconnect, and wall control mode. If power is restored and the unit runs, this was not a parts failure.
Whole-home ventilation troubleshooting
HRV / ERV Not Working? Check Power, Filters, and Airflow
Start by checking whether the HRV / ERV is dead or has power but weak airflow. Then check the breaker, service switch, plug, wall control, filters, outdoor hoods, frost, and accessible core area before assuming a fan motor or board failed.
If the display or fan is dead, prove power and the run command first. If the unit responds but air is weak, check filters, hoods, the accessible core area, and cold-weather frost before suspecting a fan motor or board.
Use the checks below to decide whether this is routine maintenance, a cold-weather restriction, a wall-control issue, or a service call for internal testing.
Don’t start with: Do not buy fan motors, boards, or wall controls from the no-airflow symptom alone. First confirm power, clear filters and hoods, a seated core, and one specific test clue.
No lights or fan?check the breaker, service switch, plug, disconnect, and wall control before opening anything.
Power but weak air?inspect filters, outdoor hoods, and the accessible core area for blockage, dust, or frost.
Do this first
- Turn the HRV / ERV off at the normal wall control before opening routine filter or core access.
- Reset a tripped breaker once only. If it trips again, leave the unit off and call service.
- Keep hands away from wet wiring, line-voltage covers, hardwired connections, and any area that smells hot.
- Do not defeat, tape down, or hold closed door switches or safety devices to make the unit run.
- Do not force a frozen core, stuck access panel, or fragile media out of the cabinet.
- Stop if you see scorched insulation, melted plastic, heavy internal ice, standing water near electrical parts, or repeated clicking.
- Save the wall-control setting, power-light behavior, fan sound, and filter/core photos before calling service.
Last reviewed: 2026-06-30
Fast HRV / ERV sorter
Does the display respond but air is weak?
Treat it as an airflow restriction first. Inspect filters, outdoor intake and exhaust hoods, and the accessible core area before pricing fan parts.
Did it stop during freezing weather?
Look for iced outdoor hoods, frost in the accessible core area, or a blocked condensate path if your unit drains water.
Do you hear one fan, humming, grinding, or clicking?
After filters and hoods are clear, those sounds point toward internal fan, wiring, or control diagnosis by service. Leave the unit off if it hums, smells hot, or clicks repeatedly.
Does the breaker trip again?
Leave the HRV / ERV off. Repeated trips are an electrical fault, not a filter-cleaning problem.
Is there water near controls or wiring?
Stop homeowner checks and call service. The next step is safe isolation and internal inspection.
Read the power, filter, and core clues
Compare power behavior, airflow, filter condition, core condition, and outdoor hood blockage before guessing at motors.
Before you buy anything
Buy a filter only after you match the exact model, size, and part number. Leave motors, controls, boards, and defrost parts for confirmed diagnosis.
What is probably happening
Most HRV / ERV failures show one of three patterns: no power, weak airflow, or cold-weather/core trouble.
- If the display is dark after one clear run command, check the access door latch, service switch, plug, disconnect, and breaker handle before opening routine access.
- If the display responds but air is weak, pull the filters and look outside at both hoods. Loaded filters, blocked hoods, or a crooked core come before internal parts.
- Cold-weather shutdowns often involve iced hoods, frost in the core area, poor airflow balance, or a drain/defrost issue. Note whether the outdoor hood is blocked or frost returns after the filters are clean.
- One fan running, repeated clicking, humming, or grinding after restrictions are cleared points toward service diagnosis.
- Guessing at a fan motor or control board before the visible airflow path is checked is the expensive mistake.
What not to do first
Rule out maintenance and control causes without creating an electrical or airflow problem.
- Do not buy a wall control because the display looks confusing. First set a clear run command such as continuous ventilation or boost.
- Do not replace a fan motor because one grille has weak airflow. Blocked hoods, loaded filters, closed dampers, or a dirty core can create the same symptom.
- Do not open line-voltage compartments, probe live wiring, or remove covers meant only for service access.
- Do not defeat door switches or safety devices to watch the unit run.
- Do not wash an ERV core or delicate media unless the unit's routine maintenance instructions specifically allow that method.
Power, filter, and airflow map
Use this map after the unit is off and routine access is safe. The best clue is what the unit does when commanded to run.
| What you see | Likely meaning | Next move |
|---|---|---|
| No lights, no fan, no response | Power or wall-control check | Check breaker, service switch, plug, disconnect, access door, and a clear run command. |
| Display responds but airflow is weak | Restriction or one-side airflow issue | Inspect filters, outdoor hoods, grilles, and the accessible core area. |
| Stopped after freezing weather | Frost, iced hood, drain, or defrost issue | Let ice thaw naturally, clear safe visible hood blockage, and note whether it repeats. |
| One fan runs or the unit hums/clicks | Internal fan, capacitor, wiring, or control fault | Stop after visible restrictions are clear and schedule service. |
| Breaker trips again or wiring smells hot | Electrical fault | Leave the unit off and call service. |
Power and control checks
A dead HRV / ERV should be treated like a power and command problem before the cabinet is treated like a failed machine.
- Set the wall control to a clear run mode, not standby, vacation, intermittent timer, or humidity-only operation.
- Look for a clearly tripped HRV / ERV breaker. Reset it once from the handle only; leave it off if it trips again.
- Look for a nearby service switch, disconnect, or plug that was turned off during cleaning or other work.
- Confirm any routine access door is fully seated if the unit uses a door interlock.
- Note whether the display is dark, normal, flashing an error, or responding to mode changes.
Filters, hoods, and core clues
Airflow restrictions are the most common safe-to-check causes of weak ventilation and cold-weather shutdowns.
- Remove user-serviceable filters and compare both sides for heavy dust, pet hair, collapse, moisture, or damage.
- Inspect both outdoor hoods for leaves, lint, snow, ice, or blocked screens from a safe position.
- Open only the normal routine-access door and look for heavy dust, frost, standing water, or a core that is not seated correctly.
- Let ice thaw naturally. Do not chip, pry, or heat a frozen core.
- Reinstall dry filters and the core exactly as labeled before restarting.
- How to clean an HRV / ERV filter — routine filter cleaning path before replacement
- How to clean an HRV / ERV core — model-dependent core cleaning guidance
Fan behavior and service clues
Once power, filters, hoods, and the accessible core are checked, listen to the fans. The sound tells you when to stop.
- Both fans start and air returns after cleaning: the problem was likely restriction or control setting.
- One fan runs while the other stays still: internal fan, wiring, or board diagnosis is likely.
- The unit hums, clicks repeatedly, grinds, or smells hot: leave it off and call service.
- The unit runs only on boost or only on one speed: note the wall-control behavior and ask for control/fan-speed diagnosis.
- The same frost or shutdown returns after filters and hoods are clear: ask for defrost, airflow balance, and drain diagnosis.
Replacement Parts
Buy a filter only when the old one is torn, collapsed, or airflow improves after it is removed. Motors, boards, and controls need confirmed service diagnosis.
HRV / ERV replacement filter
Helps when: The existing filter is torn, collapsed, will not come clean, or airflow returns after removing a visibly loaded filter.
Skip it when: The unit is dead, the breaker trips, the wall control does not respond, or one fan still will not run after the airflow path is clear.
Compare HRV / ERV replacement filters on AmazonAs an Amazon Associate I earn from qualifying purchases. Repair Riot may earn a commission at no extra cost to you.
Tools You May Need
These are for routine visual checks and loose-dust cleanup only. Stop before electrical compartments, hardwired connections, frozen cores, or unsafe outdoor hood access.
Inspection flashlight
Helps when: You are checking the lower cabinet, filter tracks, core access area, drain area, and outdoor hood openings without reaching into hidden spaces.
Skip it when: The unit is wet near wiring, smells hot, or requires opening a line-voltage compartment.
Compare inspection flashlights on Amazon
Soft brush vacuum attachment
Helps when: Removing loose dust from reusable filters and routine access areas without damaging media.
Skip it when: The filter is wet, torn, collapsing, or the unit instructions forbid vacuum cleaning.
Compare soft brush vacuum attachments on AmazonAs an Amazon Associate I earn from qualifying purchases. Repair Riot may earn a commission at no extra cost to you.
FAQ
Why is my HRV or ERV completely dead?
The most common reasons are a tripped breaker, switched-off service disconnect, loose plug, open access door, or wall control set to off or standby. If power is confirmed and the unit is still dead, the problem is likely internal.
Can dirty filters make an HRV or ERV seem not to work?
Yes. Loaded HRV / ERV filters can cut airflow enough that the system feels ineffective. Some units also reduce operation when airflow is badly restricted, especially in cold weather.
Should I replace the fan motor if I do not feel airflow?
Not first. Weak or missing airflow is often caused by dirty filters, blocked outdoor hoods, frost, closed dampers, or a dirty core area. A fan motor becomes more likely only after those checks are clear.
What if the HRV or ERV stopped during freezing weather?
Check for snow or ice at the outdoor hoods and inspect the accessible core area for frost or internal ice. Repeated freeze-ups can point to airflow restriction, drainage trouble, or a defrost issue.
Is it safe to clean the HRV or ERV core myself?
Only if the core is user-serviceable and your unit's routine maintenance instructions allow removal and cleaning. Some ERV media and coated cores can be damaged by water, soap, or rough handling.
Why does my HRV or ERV run on boost but not low speed?
That can be a wall-control setting, timer, humidity-control behavior, speed-control fault, or internal fan issue. Confirm the mode settings and airflow restrictions first, then call service if the pattern remains.
Can a blocked outdoor hood stop an HRV or ERV?
Yes. Intake or exhaust hood blockage can starve one side of the system, create frost, and make the unit noisy or weak. Clear only visible blockage from safe ground-level access.
When should I call a technician for an HRV or ERV that is not working?
Call if the breaker trips again, power is present but one or both fans will not run, or the unit hums or smells hot. Also call if water is near electrical parts or frost returns after filters and hoods are clear.
How this guide was built
Repair Riot built this page around homeowner-visible HRV and ERV clues: power response, wall-control mode, filter loading, outdoor hood blockage, accessible core condition, frost, water near electrical areas, and fan behavior. The source links support ventilation and HVAC maintenance context; the repair sequence is original guidance.
- DOE whole-house ventilation — background on whole-house ventilation systems, including heat-recovery and energy-recovery ventilation
- ENERGY STAR HVAC maintenance checklist — homeowner maintenance and professional service context for heating and cooling equipment