Humidifier Repair

Under certain weather conditions, comfort means putting water into the air of your home. This Fix-It Guide on humidifier repair tells how a humidifier works, what often goes wrong, how to identify a humidifier problem, and what parts and tools you will need to fix it. It then gives simple step-by-step instructions for how to service an evaporation pad on a pump humidifier, how to service the float control, and how to service the humidistat.You may also be directed to electrical cord repair, switch repair, motor repair, and fan repair as needed.

How Does a Humidifier Work?

A humidifier is an appliance designed on the principle of evaporation to increase moisture in the air. Water from a reservoir is added to an evaporation pad. A fan blows air through the pad. Fine droplets of water are placed in the air, thus increasing the humidity of the room. Both room and tabletop humidifiers work on this principle.

The two types of evaporative room humidifiers are drum and pump. A drum humidifier gathers water into an evaporation pad by immersing the pad, wrapped around a drum, into a reservoir of water. Water dripping from the rotating pad is absorbed by air current produced by a fan. A pump humidifier uses a pump to gather water from the reservoir and distribute it through the evaporation pad. Air from the fan blows through the pad and picks up the droplets to moisturize the air. Both types of humidifiers have operational controls, an evaporation pad, a fan, a water reservoir, and a humidistat. Some Forced-Air Distribution systems include an evaporative humidifier that works in the same way.

An ultrasonic humidifier works on completely different principles from standard room humidifiers. It’s electronic. Beyond normal cleaning and testing of the electrical cord or switch, service of an ultrasonic humidifier should be left to a service technician.

What Can Go Wrong with a Humidifier?

As you see, evaporative humidifiers are relatively simple appliances. Many humidifier problems result from dirty or damaged evaporative foam or filters. The electrical cord may malfunction. The humidistat, float control, and fan can be faulty.

The humidistat is sensitive to the level of moisture in the air. If humidity is lower than the control point set, the humidistat turns on the fan and pump (or pad rotator). See below for service instructions.

Many humidifiers have a hollow float inside that helps control water level, or tells the operator (that’s you) when to refill the reservoir. In some cases, you’ll need to adjust or replace the float (see below).

Fix-It Tip

Humidifier water conditioners are available that can soften the water and reduce algae to make your unit last longer. Stay away from those with perfumes that can leave residue to clog the evaporator pad. Clean the unit with a disinfectant at least once a season.

How Can I Identify a Humidifier Problem?

 Humidifier Repair

Test the fan motor using a multimeter.

  • If the unit doesn’t work, check the water level and fill if low. Make sure power is on at the outlet and test the electrical cord. Test and service the humidistat if it is faulty (see below). Also check the float control and service it if it is faulty (see below).
  • If the humidifier doesn’t sufficiently increase humidity, check the evaporation pad and service it if it is dirty. Also check the humidistat and service it if it is faulty (see below).
  • If the humidifier is noisy, test the fan motor and service it or replace it if it is faulty.
  • If the humidifier smells bad, check the evaporation pad and clean or replace it; check the water reservoir and clean and refill it if it is dirty.

What Do I Need for Humidifier Repair?

The most important replacement part on most humidifiers is the evaporative pad. Fortunately, you can find replacements for most popular models at local hardware stores. If you can’t find parts, refer to the unit’s owner’s manual for information on ordering replacement parts.

You’ll need a few tools to check and fix a humidifier:

  • Screwdrivers
  • Wrenches
  • Multimeter

What Are the Steps to Humidifier Repair?


Humidifiers run on electricity with water, so it’s vital that you unplug the humidifier before attempting to repair it. Safety first!

Service an evaporation pad on a pump humidifier:

  1. Unplug the humidifier or otherwise make sure that power to the unit is off.
  2. Lift the pad frame from the humidifier housing and hold it so excess moisture will drip back into the reservoir.
  3. Remove the pad from the frame.
  4. Rinse the pad with clean water or replace it. If you use soap or detergent, make sure the pad is completely rinsed of residue before reinstalling.
  5. While the humidifier is open, clean the reservoir and inspect the inside of the appliance for any obvious problems.

Service a humidifier float control:

  1. Remove the top cover and inspect the float. Make sure the float rod is straight and secure and that the float is clean. When cleaning the float, make sure you don’t bend the rod.
  2. Move the float manually to determine at what level the float switch is activated. If necessary, adjust the switch to make sure it activates at the appropriate level.
  3. Check all electrical connections on the float switch to make sure they are tight.

Service a humidifier humidistat:

  1. Mark and disconnect any wires attached to the humidistat.
  2. Use a multimeter to test the humidistat. It should conduct in the on position, but not in the off position.
  3. If necessary, replace the humidistat with an exact replacement part.

Fix-It Tip

Remember to lubricate the humidifier fan at least twice during each season it runs. Use a few drops of machine oil.