Why and when to reset an Aprilaire humidifier
An Aprilaire humidifier reset clears the unit's memory and restarts its control board, which solves most common problems: the humidistat not responding, the unit running constantly, error codes on the display, or the system not turning on at all. A reset is not the same as a power cycle—flipping the breaker for a few seconds. A true reset wipes stored settings and forces the humidifier to recalibrate.
You should reset your Aprilaire before calling a technician, because the fix often takes two minutes and costs nothing. Reset the unit if it stops responding to your thermostat, if it runs without stopping, or if the display shows a fault code. If the humidifier still does not work after a reset, the problem is likely a failed sensor, a clogged water line, or a broken control board—all things a technician needs to diagnose.
Key Takeaways
- Most Aprilaire humidifiers reset by holding the power button for 10 to 15 seconds until the display goes blank, then releasing it.
- Some models have a dedicated reset button on the control board inside the unit; check your manual to see which type you own.
- After a reset, the humidifier returns to factory settings, so you will need to set your target humidity level again on the thermostat or humidistat.
- A reset clears error codes and restarts the control board but does not fix mechanical problems like a clogged water line or a failed humidistat sensor.
- If the humidifier still does not work after a reset and a power cycle, the control board or sensor has likely failed and needs professional replacement.
Reset using the power button on your thermostat or humidistat
The easiest reset method works on most Aprilaire models: hold down the power button on your thermostat or humidistat for 10 to 15 seconds. Watch the display—it should go blank or show a brief message. Release the button and wait 30 seconds for the unit to restart. The display will light up again, and you should see the humidifier return to its default state.
This method works because the thermostat and humidifier communicate through your HVAC system's wiring. Holding the power button sends a reset signal down that line. After the restart, your target humidity setting will be gone, so you will need to set it again using your thermostat's menu. Check your thermostat manual for the steps—most modern units have a "Humidity" or "Humidifier" setting in the main menu.
Reset using the button on the control board inside the unit
Some Aprilaire models, especially older ones or those with a standalone humidistat, have a physical reset button on the control board inside the humidifier cabinet. To access it, turn off the power at your breaker, then open the humidifier's access panel or front cover. Look for a small button labeled "Reset" or a recessed button you press with a paperclip or pen.
Press and hold the reset button for 3 to 5 seconds, then release it. Close the cabinet, turn the power back on at the breaker, and wait 30 seconds for the unit to boot up. The display or indicator light should show that the humidifier is ready. If you cannot find a reset button inside your unit, your model uses the thermostat method instead—check your manual or the Aprilaire website for your specific model number.
What happens after you reset
After a reset, your Aprilaire humidifier returns to factory defaults. The target humidity level you set before will be erased, and the unit will not run until you set a new humidity target. On most thermostats, this means going into the menu, finding "Humidity" or "Humidifier," and entering a number between 30 and 50 percent—most homes do well at 40 percent in winter.
The humidifier will also recalibrate its sensors. If the unit has a humidistat (a sensor that measures moisture in the air), it will take a few minutes to read the current humidity and begin normal operation. During this time, you may see the display flicker or show a brief code—this is normal. If an error code stays on the display after 5 minutes, the sensor may be faulty and need professional service.
When a reset does not fix the problem
If the humidifier still does not work after a reset and a full power cycle (turning off the breaker for 5 minutes, then back on), the issue is not a software glitch. Common hardware failures include a clogged water inlet line, a failed humidistat sensor, a broken control board, or a stuck solenoid valve that controls water flow.
Check the water line first: turn off the power, locate the water inlet line (usually a small plastic tube connected to your cold water line), and look for mineral buildup or kinks. If the line is clogged, you can try flushing it with distilled water, but if the humidifier still does not respond after that, call a technician. A failed control board or sensor requires replacement and is not a DIY fix.
How to find your Aprilaire model number and manual
Your Aprilaire model number is printed on a label inside the humidifier cabinet or on the back of the unit. It usually starts with a number like 500, 600, 700, or 8000 series. Write down the full model number—it may include letters or a dash—because different models reset differently.
Go to aprilaire.com and use their product search to find your manual. read the PDF and search for "reset" to see the exact steps for your model. If you cannot find your manual online, call Aprilaire's customer service line (the number is usually on the unit itself or on their website). They can walk you through a reset over the phone and help you troubleshoot if the reset does not work.
Preventing the need for frequent resets
If your Aprilaire humidifier needs a reset every few months, something is causing the control board to fail repeatedly. The most common cause is mineral buildup in the water line or on the evaporator pad, which forces the board to work harder and overheat. Use distilled water instead of tap water—it costs a few dollars a gallon and prevents mineral deposits that clog sensors and valves.
Change or clean the evaporator pad every heating season (usually in fall before you turn the humidifier on). A dirty pad reduces water absorption and makes the humidistat work overtime trying to raise humidity. If you live in a very dry climate or run the humidifier constantly, the pad may need cleaning mid-season. A clean pad and distilled water will cut down on resets and extend the life of your unit by years.
Frequently Asked Questions
Will resetting my humidifier erase my humidity settings?
Yes. A reset returns the humidifier to factory defaults, which means your target humidity level is erased. After the reset, you will need to set your desired humidity again using your thermostat or humidistat. Most people set it between 35 and 45 percent in winter.
How long does it take for an Aprilaire humidifier to work after a reset?
The unit should restart within 30 seconds of a reset. The humidistat sensor may take another 2 to 5 minutes to read the current humidity level and begin normal operation. If the humidifier does not respond after 10 minutes, try a full power cycle by turning off the breaker for 5 minutes.
Can I reset my humidifier without turning off the power?
Yes, if your model has a reset button on the thermostat or a dedicated reset button on the control board. The thermostat method does not require you to go to the breaker. Only the internal control board reset requires you to turn off power first for safety.
What does it mean if my humidifier shows an error code after a reset?
Error codes usually point to a specific problem: a clogged water line, a failed sensor, or a stuck valve. Check your manual for what the code means. If the code clears after 5 minutes, it was likely a temporary glitch. If it stays, the part it refers to probably needs professional service.
Should I reset my humidifier if it is running constantly?
Yes, a reset is the first step. Constant running usually means the humidistat sensor is not reading humidity correctly or the control board is stuck in a loop. A reset often fixes this. If the humidifier runs constantly after the reset, the sensor or board has likely failed and needs replacement.