Sunday night the house was a bit warm and I set the temperature a couple of degrees lower on the thermostat. A short while later, I noticed that no air was coming from the registers and the outside compressor unit wasn’t running. I performed a couple of quick diagnostic checks:
- The thermostat relay was making an audible “click” when the temperature setting is lowered and the electronic display said the system was ON. This is good.
- The main circuit breakers for the inside air handler and outside compressor were not tripped, so the power wasn’t the problem.
- Taking a look at the condensate removal pump on the basement floor next to the air handler, I noticed 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.
Little Giant Automatic Condensate Removal Pump VCL-24ULS
“Oh great!” I thought to myself. It’s Sunday night and the hardware stores are all closed. There’s no chance of getting a replacement condensate pump tonight. I could call an A/C repairman for an after-hours visit – but there was another less expensive solution…
Temporary Fix
As a temporary fix so I wouldn’t be sweating all night:
- I unplugged the condensate pump.
- Removed the four corner screws to the cover of the pump.
- Removed the cover with the pump motor and mechanism off the water reservoir.
- Carried the water reservoir outside and dumped the water.
- Reassembled the pump.
- Plugged in the pump power cord.
Now that I had an empty water reservoir, the float switch reset allowing the A/C system to operate. I had bought myself a couple of hours to sleep in comfort until the reservoir was full again. With the cooler outside temperature that night, the A/C reservoir was only 1/2 full the next morning.
Finding a Replacement Condensate Pump
The big box hardware stores in my area have condensate removal pumps, but not the brand or horsepower rating of the pump that I have. The online product reviews for the pumps in the big box stores were very negative, so I nixed the idea of buying a cheaper (~$70) pump that had a bad reputation.
My pump is a Little Giant Pump Company model VCL-24ULS with a 1/18 HP motor, 1 gallon water tank and will lift 150 gallons of water per hour to 17 feet high.
If you’re looking for a wiring diagram, see the Operating and Maintenance manual.
Little Giant Condensate Removal Pump
The new pump, installation instructions and sticker with a notice to clean the pump when changing the AC/Heater filters.
Little Giant Condensate Removal Pump VCL-24ULS
Installing the Condensate Removal Pump
The new pump was simple to install – the job took no more than 10 minutes.
Here are the new and old pumps. The old pump died after almost 9 years. The dusty look of the old pump is from overspray when the contractor painted the drywall when the house was built.
Old Pump and New Pump
Remove the Old Pump
My pump has two input lines:
- Rigid white 3/4 inch PVC drain pipe from the A/C unit
- 3/8 inch clear flexible tube from the humidifier (used in the winter with heating)
and one discharge line:
- a clear 3/8 inch flexible discharge tube that connects to the overhead sewer line
To remove the old pump:
- Turn off the AC/heater system at the thermostat.
- Disconnect the power cord to the pump.
- 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.
- Remove the flexible 3/8 inch discharge tube from the barbed nipple.
- Remove the four cover screws at the corners of the pump.
- Lift up the pump cover and slide the water reservoir away from the the PVC drain pipe.
I needed to remove the cover because the rigid 3/4 inch PVC drain pipe extended an inch or two below the cover and I needed to tilt the reservoir to clear the pipe. - Clean the drain pipe and lines with bleach and water.
- Set the new pump in place.
- Reconnect the drain and discharge lines.
- Reconnect the safety shutoff switch wires.
- Reconnect the power to the pump.
- Turn on the AC/heater at the thermostat.
- Fill the pump basin with water and test.
Disconnect the Piping
Remove the cover screws and lift off the pump.
Remove the Pump Cover
Yuck! Everything is covered in crud. It’s remarkable the pump lasted almost 9 years. I see why the new pump includes a sticker for the service technician to clean the pump and basin when changing the AC/heater air filters.
Old Pump Covered in Crud
I removed the cover of the new pump because the instructions indicated there might be packing material inside. I found none.
Note that the pump has two float switches (click on the image below for a full size view):
- 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 water mark is reached, it triggers the pump On switch to pump out the condensate water.
Condensate Pump Floats
The new pump was simple to install. Just reattach the safety cutoff switch wires (yellow wire nuts – the order of the wires doesn’t matter, it’s a simple switch), insert the drain lines and reattach the discharge line to the barbed nipple. I filled the pump with water through the hole at the front-right corner to check the operation and look for leaks around the barbed nipple. Everything worked fine!
New Condensate Removal Pump Ready for Service
Note to self: Clean the condensate pump each time the AC/heater air filters are changed.
Cause of the Old Pump Malfunction
The cause of the malfunction 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.
Now when I change the A/C air filter, I also clean the condensate pump. To clean the pump:
- Turn off the A/C unit.
- Unplug the pump power cord. Water and electricity don’t mix!
- 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.
I pay particular attention to wiping down the metal float shaft and checking that it moves freely.
Hope this saves you some buck$.
Bob Jackson
June 4th, 2009 at 6:55 am
How to Replace a Broken Air Conditioner Condensate Pump | HandymanHowto.com great article thank you.
July 30th, 2009 at 2:26 pm
Excellent work. Thank you for detailed explanations, pictures and diagrams.
Please continue. My next project is replacing condensation pump, and I feel more confident after reading your site.
January 18th, 2010 at 2:54 pm
Great explanation. I thought there was a float switch in there, but none of the manufacturers discuss it online. Your description assured me it was a good idea to open up the pump – sure enough, the float switch was junked over and all I needed to do was clean it. Works like a charm now! Another good thing to always do, half a cup of bleach into the condensate drain every time you replace a filter. Thanks again!
January 18th, 2010 at 6:08 pm
Thanks for letting me the article helped you. – Bob Jackson
February 28th, 2010 at 4:10 pm
Thank you so much for your help. I was so glad I found your article because I had no idea what to do when the unit was leaking. Haven’t tried the repair yet, but even if it doesn’t work I also know how to install a new one. Keep up the great work !!
May 5th, 2010 at 10:39 am
Found water on the basement floor – pump running constantly – turning off/on thermostat and unplugging pump power did not help. Searched online and found your article – tho my pump is not the same and smaller – the principle should be the same so I’ve opened the assembly – it has crud but not bad enough – float seems to move freely too – BUT after emptying the container – found a small frog floating in the water;must have been the obstraction that’s preventing the float to function. Re-installed unit – seems fine now.
May 26th, 2010 at 1:56 am
This was an awesome article, and it seemed to be pointed right at me. Love it!!! Thanks
May 26th, 2010 at 4:31 am
You’re welcome. It’s amazing what you can find on the web on just about any topic.
July 7th, 2010 at 8:58 am
Thanks for this write-up. My pump and the tubing that connects the A/C to the pump seem to be fine, however, the tubing that removes the water from the pump popped off on the sump side. We’ve been running it longer than usual so it might have just hit it’s wear point. The ring fastener looks OK, so I think I just need a replacement tube.
Until I get to the hardware store, I was able to soak up the water with a towel and get it 99% dry and hopefully let the A/C run for a bit without spraying water everywhere.
Thank you again for a great write-up.
September 2nd, 2010 at 12:25 pm
Thank you so much for this article. My basement has been flooding for the last month on random days of the week. I initially called to HVAC folks to look at the air conditioner unit and after being told it may have been clogged, they cleaned the clog and left. Two days later I called again after the flooding re-occurred. I was told they found nothing and left. A week and a half later I called again to be told to look at my water conditioner system which happens to be in the same area. I was told to look at the backwash day and see if the flooding happens around the same time. Since then I have run the backwash on a day when I was home to observe it and everything was fine. On Monday I came home to see the PVC leading to the condensate pump disconnected and water over everything. I fixed that and glued the PVC back together and thought, finally, I have fixed the problem. Then today, my Mother called me at work to say the flooding occurred again. This frustrated me so much I started to look for a license water treatment contractor. One of my handyman friends said he was 99% sure is was not the water treatment system, but the float in the condensate box. I started googling the internet and came upon your handout. I was so so frustrated, but after reading your pamphlet (by the way my condensate box is the same as your new one) I feel confident I can go home today and fix my problem once and for all (be it the float or replacement). So with that, (I know this is lengthy but you have to feel my frustration) I will again say THANK YOU! THANK YOU!
P.S. I have made this website a favorite.
Ms Trini.
September 2nd, 2010 at 6:57 pm
Thanks for taking the time to write and letting me know my “How To” project helped you.
Bob