How to Fix Humidity Control Issues Found in an Older Humidifier

humidifier next to old radiator
  • 2-4 hours
  • Intermediate
  • 20-100
What You'll Need
Humidifier owner's manual
Furnace service manual
Screwdriver set
Adjustable wrench
Replacement float valve
Replacement water supply valve
Replacement filter pad
Replacement filter pad rotation motor

In older humidifiers, humidity control problems can manifest themselves in a variety of ways, mostly due to clogged or worn-out parts. Follow the process below to identify and fix humidity control issues that can be found in older humidifiers.

1. Indoor Air is Not Humid Enough

Determine whether your humidifier is providing insufficient air moisture or too much. In recently-built homes that are tightly sealed from outside air, the air may still be too dry when the furnace humidifier runs at the same time as the furnace. You may need to add a freestanding humidifier on the main floor. Another option is to run the furnace fan all the time, so the humidifier will operate continuously. However, the electricity used to run the fan constantly will be expensive.

2. Indoor Air Is Too Humid

The humidifier may be drawing too much water, and overflowing its reservoir. You will need to replace the float valve that controls the water depth in the reservoir. The filter pad may be saturated or clogged. Replace the humidifier filter pad with a clean new one. The humidistat may be set too high. Adjust the humidistat to between 45 and 50 percent humidity.

3. The Humidifier Does Not Operate

The humidifier may not operate when the furnace is turned on. Turn the humidifier up to between 60 and 65 percent humidity, then turn your furnace thermostat up to 5 degrees higher than your preferred room temperature. When the furnace fan comes on, the humidifier should function correctly. If the humidifier does not work, check the electrical connections, and the internal components, including the float valve, motor and transformer to make sure they are functioning correctly. If these electrical and operating components are fine, check the water supply to the reservoir and to the filter pad. Look for leakage along the tubing or inside the humidifier itself, and replace the leaking parts.

4. Inadequate Water Supply

The humidifier may be getting some water, but not enough to maintain the humidity level you desire. Check the water supply valve to the humidifier, including the water supply valve and water intake pipes. Remove the water inlet line and check the water supply valve for mold or mineral deposits that can clog it. Clean the valve with a small nylon brush and reattach it to the humidifier. If water is still not flowing into the humidifier, replace the water supply valve.

5. The Filter Pad Does Not Spin

The humidifier filter pad is turned by a motor mounted on the side of the humidifier unit. The motor should spin the filter pad to allow aeration of the water in the humidifier. If the motor does not come on when the furnace fan starts, check the electrical circuit to the motor, and the water supply to the filter pad. Replace the motor if defective, and the filter pad if it is clogged with mineral residue from your water supply.