The part(s) or condition(s) listed below for the symptom Humidifier not getting water are ordered from most likely to least likely to occur. Check or test each item, starting with the items at the top of the page.
The water inlet valve is an electrically-controlled valve that opens to allow water to enter the humidifier. If the water inlet valve is clogged or defective, the humidifer will not fill with water. Use a multimeter to test the valve for continuity. If the water inlet valve does not have continuity, replace it. In addition, test the incoming power to the valve. If the water inlet valve has continuity and is getting power, but the humidifier won't fill with water, it is possible that the valve is clogged. If the water inlet valve is clogged, replace it.
The saddle valve is a small brass water supply valve which is often clamped to a copper household water supply pipe. Over time, the saddle valve can become clogged with sediment or calcium deposits. Because it is difficult to clean a saddle valve thoroughly, and because the replacement cost is fairly low, we recommend replacing the saddle valve if it is restricted.
If the humidistat is incorrectly set or isn't working properly, the humidifier won't fill with water. To determine if the humidistat is defective, turn the humidistat to the highest setting and listen for a "click." If you do not hear a click, this indicates that the electrical contacts inside the humidistat are not closing. If you do hear a click, but the humidifier still won't fill with water, it is more likely that another part is defective.
Some furnaces have a separate transformer to provide 24 volts to the humidifier. If the water inlet valve is not receiving 24 volts and the contacts in the humidistat are closing as expected, it's likely the transformer has failed and the component will need to be replaced.
A drum style humidifier will use a float to regulate the amount of water entering the humidifier. When the tray fills with water to a certain point, the float will rise up and shut off the water inlet valve. A damaged float may not allow the inlet valve to open at all, resulting in the humidifier not getting any water. Inspect the float to determine if it is obstructed or damaged and replace if necessary.
The water supply saddle valve is a small brass water supply valve which is often clamped to a copper household water supply pipe. Over time, the saddle valve can become clogged with sediment or calcium deposits. Because it is difficult to clean a saddle valve thoroughly, and because the replacement cost is fairly low, we recommend replacing the saddle valve if it is restricted.