Direct answer: An HRV or ERV that runs constantly is usually being told to run by a wall control, dehumidistat, timer, or stuck boost switch. Dirty filters and restricted airflow can also keep it from dropping back to normal operation.
Most likely: Start with the control side first: fan mode set to continuous, a bathroom boost timer left on, or a humidity setting that keeps calling for ventilation.
First figure out whether the unit is supposed to be running all the time or whether it is ignoring the controls. That split saves a lot of wasted time. Reality check: many HRVs are designed to run often, but not every house needs full-time high speed. Common wrong move: turning random dials and dip switches without noting the original settings.
Don’t start with: Do not start by ordering a motor or control board. On these units, constant running is more often a settings or low-airflow problem than a failed major part.
You hear the unit most of the day, but it does not sound like full boost. Indoor air may seem normal.
Start here: Check whether the main control is set to continuous ventilation or a low-speed run mode before assuming a fault.
The unit sounds louder than usual and stays there, often after a shower, cooking, or using a timer switch.
Start here: Look for a stuck boost switch, timer, or humidity control still calling for high speed.
You change modes or turn the control off, but the unit keeps running the same way.
Start here: Verify power to the wall control and look for a failed control, shorted low-voltage wiring, or a relay stuck closed in the unit.
The unit seems to stay on during rainy or muggy days, especially in shoulder seasons.
Start here: Check the humidity setting first. A dehumidistat set too aggressively can keep the unit running far more than expected.
This is the most common reason. Many HRV and ERV controls have low-speed continuous, intermittent, and boost modes that are easy to misread.
Quick check: At the main wall control, look for settings like continuous, min, exchange, or ventilation and switch temporarily to standby or intermittent if your control allows it.
A spring timer, push-button timer, or bath switch can keep calling for high speed if it sticks mechanically or electrically.
Quick check: Press each boost control you can find, let timers expire, and see whether the fan sound drops back after a few minutes.
If the dehumidistat is set to chase a very low indoor humidity level, the unit may run almost nonstop in damp weather.
Quick check: Raise the humidity setpoint slightly and watch whether the unit finally cycles down after 10 to 20 minutes.
Restricted airflow can make the unit run longer and louder, and some controls respond poorly when the unit cannot move air normally.
Quick check: Open the access panel with power off and inspect the filters for dust matting, pet hair, or a gray felted surface.
A lot of constant-run complaints turn out to be normal operation with the wrong mode selected. This is the safest and fastest check.
Next move: If the unit slows down or stops, the system was being commanded to run. Leave it in the desired mode and monitor it through the day. If the unit keeps running exactly the same, move on to boost controls and humidity calls.
What to conclude: The first split is simple: either the controls are asking for ventilation, or the unit is ignoring them.
A stuck boost call is the next most common cause, especially when the unit is stuck on high speed after showers or cooking.
Next move: If the unit drops back after one timer expires or one switch is reset, that control was holding the unit on. If nothing changes, check the humidity control and the unit filters next.
What to conclude: When the fan is stuck on high but still responds eventually, the problem is usually upstream at a timer or switch, not the fan motor itself.
An aggressive dehumidistat setting can keep an HRV or ERV running much longer than homeowners expect, especially in damp weather or tight houses.
Next move: If the unit settles down after a modest humidity adjustment, the setting was too aggressive for current conditions. If the unit still runs the same way, inspect airflow restrictions inside the unit.
Filters are one of the few homeowner-service items on these units, and restricted airflow can make the whole system act wrong.
Next move: If airflow sounds smoother and the unit returns to normal timing, the restriction was likely the main issue. If clean filters do not change anything and the unit still ignores controls, the fault is more likely in the wall control, relay, or internal control circuit.
By now you should know whether this is a settings problem, a stuck external call, or an internal electrical fault that is not a good DIY guess-and-buy job.
A good result: If the corrected control or fresh filters solved it, you are done. Keep a note of the working settings so the problem does not come back after someone bumps the controls.
If not: If the unit still runs nonstop with no clear control response, stop at diagnosis and get a pro to test the control circuit safely.
What to conclude: Constant running that ignores controls is usually not a filter problem anymore. It points to a control-side fault that needs proper electrical testing.
Repair Riot may earn a commission from qualifying purchases, at no extra cost to you.
Sometimes, yes. Many HRVs are set up for continuous low-speed ventilation, especially in tighter homes. The problem is when it runs on high speed constantly, ignores the controls, or runs much more than your normal settings call for.
Usually a bathroom boost timer, humidity control, or override switch is still calling for ventilation. Start by checking whether the timer actually returned to off and whether the humidity setting is too low for current indoor conditions.
They can contribute. Dirty HRV or ERV filters restrict airflow and can make the unit sound strained, run longer, or behave poorly. They are not the only cause, but they are one of the first things worth checking.
If one control or timer consistently keeps the unit running and the rest of the system responds normally otherwise, that control is suspect. If the unit ignores every control and only stops when power is cut, the problem may be inside the unit instead.
Not as a first move. A bad fan motor is not the usual reason an HRV runs constantly. Start with settings, boost calls, humidity control, and filters. If the unit ignores controls, have the control circuit tested before buying major parts.