AC Condensate Pump Repair Guide

Posted by: Mas Broto
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AC Condensate Pump Repair Guide

An Air Conditioner condensate pump is an integral part of your HVAC system. When it’s failed, your system will continue to dump condensate into the drain pan and trigger the overflow safety switch to shut off the AC. Here is a guide to troubleshoot and repair the broken HVAC condensate pump.

A condensate pump is used when a gravity (or downhill sloping) condensate drain line to either the outdoors or a floor drain isn’t feasible. For example, when the air handler is located in the basement.

My home has two air handlers: one in the attic with a gravity condensate drain line to the outdoors and another in the basement with a condensate pump.

How Do Condensate Pumps Work?

AC Condensate Pump

The pump reservoir collects the condensate water from the AC evaporator coil drain line and/or the excess water from the whole house humidifier mounted to the air handler.

An AC float switch activates the condensate pump when the reservoir is full. Then pump out the water to an overhead sewer line or drain some distance away.

If the water level rises to the high water mark, the float switch will activate a safety cutoff relay to turn off the air conditioner to prevent flooding.

Why is My AC Condensate Pump Not Working?

The cause of a broken AC condensate pump was the extensive build-up of crud on the float shaft. This prevented the On/Off float from rising with the water level to turn on the motor. The float would move with hand pressure, but it was too stiff for its natural buoyancy to lift with the rising water level.

AC Condensate Pump Troubleshooting & Repair

Before replacing the condensate pump, you may need to troubleshoot the old pump first. Sometimes, it only takes a simple fix to get the pump to work again. A temporary fix for the broken condensate pump wouldn’t sweat you all night.

Perform a quick diagnostic check on the air handler. If the thermostat relay is making an audible click when the temperature is lowered, the electronic display says the system was ON. This is good.

If the main circuit breakers for the inside air handler and outside compressor were not tripped, the power wasn’t the problem.

Take a look at the condensate removal pump next to the air handler on the basement floor. If it was full of water, the safety cutoff float switch had tripped due to the high water level to turn off the A/C system to prevent flooding.

How to repair a broken AC Condensate Pump:

  1. Unplug the condensate pump.
  2. Remove the four corner screws to the cover of the pump.
  3. Remove the cover with the pump motor and mechanism off the water reservoir.
  4. Carried the water reservoir outside and dumped the water.
  5. Reassemble the pump.
  6. Plug in the pump power cord.

The float switch reset itself now that the pump reservoir was empty, allowing the A/C system to operate. The air conditioner will run for several hours until the reservoir is full again. With the cooler outside temperature that night, the A/C reservoir was only 1/2 full the next morning.

How to Clean AC Condensate Pump

Whenever you change the AC air filter, also clean the condensate pump. Here is how to clean the AC condensate pump:

  • Turn off the A/C unit.
  • Unplug the pump power cord.
  • Remove the four screws from the metal cover.
  • Wash the basin with soap and warm water.
  • Wash and wipe down the submerged parts of the pump.

Pay attention to wiping down the metal float shaft and checking that it moves freely.

Condensate Pump Replacement

An AC condensate pump was simple to replace and install, and the job took no more than 10 minutes.

Here is the step-by-step guide on how to install the new condensate pump:

  1. Turn off the AC/heater system at the thermostat.
  2. Disconnect the power cord to the pump.
  3. Remove the wire nuts that connect the AC/heater safety shutoff wires to the float switch. This is a low voltage circuit – typically between 12 and 24 volts.
  4. Remove the flexible 3/8 inch discharge tube from the barbed nipple.
  5. Remove the four cover screws at the corners of the pump.
  6. Lift up the pump cover and slide the water reservoir away from the PVC drain pipe.
  7.  You need to remove the cover because the rigid 3/4 inch PVC drain pipe extends an inch or two below the cover, and you need to tilt the reservoir to clear the pipe.
  8. Clean the drain pipe and lines with bleach and water.
  9. Set the new pump in place.
  10. Reconnect the drain and discharge lines.
  11. Reconnect the safety shutoff switch wires.
  12. Reconnect the power to the pump.
  13. Turn on the AC/heater at the thermostat.
  14. Fill the pump basin with water and test.

Note that the pump has two float switches. Float for the high-water safety cutoff switch. The switch controls a low voltage circuit. When the switch is triggered, the air conditioning unit will shut down to prevent flooding.

Float for the On/Off switch. This float rises and falls with the water level in the basin. When the high watermark is reached, it triggers the pump On switch to pumping out the condensate water.

Cost to Replace Condensate Pump

The cost to replace a condensate pump is between $125 and $300. The part itself usually costs $50 to $300.

Avoid buying a cheap condensate pump that has a bad reputation. A brand like Little Giant is recommended. You can find a wide variety of Little Giant condensate pumps and other removal pumps at

I hope this AC troubleshooting and repair guide saves you some bucks. The best way to prevent condensate pump malfunction is to schedule regular AC maintenance. It will keep your air conditioner working optimally and extend its lifespan.

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Mas Broto

Have been in the heating and air conditioning (HVAC) industry for over 20 years. He is person that will grow and thrive to learn more about the HVAC industry throughout his career. Mas Broto is also a blogger, who's dedicated to bringing you the best knowledge to get ahead in the game of life.

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