most common AC problem – blower doesn’t come on – HVAC condensate overflow shut-off device problem

Here is a documentary on how I replaced a HVAC condensing overflow shut-off device. It’s very common for a stopped-up drain to trigger this device and result…

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  • DIY Tinker says:

    If your diagnostic is correct, then the next thing to check is the blower motor. Its the blower connected to the furnace and evaporator coil. Usually located in the garage or a closet.
    If the blower runs strong, then you want to see if the ducts are clogged. Two common scenarios are frozen evaporator or a collapsed duct.
    If you turn off the AC for 2+ hours, turn it back on and you have good/improved airflow then you have a frozen evaporator issue. Cleaning the evaporator coil will fix it.

  • jaymeez says:

    Hey can you please check the 3 minute video I put up. I actually show what my system is doing.  Thanks

  • Greg Alejanderian says:

    Hey just wanna say you have great videos up..very educational to the public, students in the trade and i bet some technician s out there

  • GalaXy808 says:

    I have question, all the ac has a over flow switch? I wanna know bec. If they have the same like the chiller ac.thank you.good video

  • DIY Tinker says:

    To my understanding, Not all come with an overflow switch. But it is common for HVAC professionals to install an overflow switch in central air units.
    I never seen a window unit AC with an overflow switch. Window units usually drain at the condensate pan. if water overflows by tilting or clogged, then the fan might kick some water in the air.

  • GalaXy808 says:

    (:thanks for the answer.

  • brandon dabaghi says:


  • Michael Solow says:

    Why do you go to the circuit breakers first, why not just switch the thermostat to “ON”, that will tell you if the transformer gets power and if it does power is coming to the unit.

  • DIY Tinker says:

    good point, and your approach is removes a few steps. But, checking the breaker is easier (no DMM required) and it at least eliminates a short circuit scenario. Also, I am trying to describe the situation by showing what all ive checked.

  • 797diablo says:

    Hi, I have a question. On your thermostat. It shoes FAN: auto. I have the same thermostat and mine also says FAN: auto. I want to turn off fan but it either goes to auto or on. Is there a way to get the off option? please let me know.

  • DIY Tinker says:

    this thermostat is at my friends house. but all thermostat can turn the FAN completely off. All you have to do is set FAN to auto, then turn the thermostat OFF. I am guessing if you press the system button, it will go from Cold to Hot to OFF. If that didnt work then let me know and ill call my friend.

  • Dennis Ellison says:

    After running without a problem for three days, my central AC died. I had an AC repair guy check it out. He added freon, checked the circuits and it ran. However, about three hours later it died again. He had suggested a $400 pump so that the condensate would not backup. However, it backed up only once in five years. Of course, he did not suggest changing the low cost backup switch. Any thoughts or suggestions? Thanks! Dennis

  • Michael Solow says:

    My way also does not require using any testers

  • DIY Tinker says:

    So, your AC has so much water from condensation that the overflow switch trips all the time? Sounds like a draining issue. I am guessing your AC in the basement? Not sure why you need a $400 pump, there are alot of cheaper ones out there that are less than $100.

  • FordRVRefrigeration says:

    Good video thanks

  • Dennis Ellison says:

    Thanks for your prompt reply! To clarify, the condensate shut off the AC only once in five years. The repair guy checked the drain pipe, and it was not backed-up. Also, the unit (not the outdoor compressor) is mounted above the garage so that the water flows down hill. Whatelse would cause the AC to shut off so soon after being “repaired”? Thanks again.

  • DIY Tinker says:

    Well, many things could still go bad… there isnt enough to go off. You could try removing the overflow shutoff and tie the red wire directly to the red contact. Just to eliminate if the overflow shutoff is the issue. If it still doesnt come on, then you know its not due to the overflow shutoff.

  • Dennis Ellison says:

    Thanks for your help. I’ll try it.

  • Danny Smith says:

    call Magic Touch appliance repair if there any problem with washing machine,dryer, refrigerator, water heater, air conditioning, heating repair Hollywood 800-315-9134

  • bendelgado3 says:

    Thank You!! I’ll check that right away

  • HVACR1Training says:

    Did you know a tech could earn over $100 an hour servicing HVAC appliances ON RVs?

  • Aaron Clark says:

    could you have just done away with the switch and got it running? just asking

  • DIY Tinker says:

    yes, you can. usually thats a temporary fix. But then you dont have a safty against condensation, and you should fix the condensation drainage if its not draining correctly.

  • imran khan says:

    i repair my central a c every year

  • Nate F says:

    Mr. Tinker, I followed your instructions. My furnace has a switch rather than a 3 prong plug. I flipped the switch and the whole thing reset! I have nice cool air. I didn’t have to wait for a tech or pay several hundred dollars. You gave me the info to fix my problem by 0:50. Thanks again.

  • Tweetygale says:

    I have a question, my HVAC will not come on. We checked the power source etc, and found out that on the condensate overflow shut off device the black thing inside is down (no water in the tube) but when you push that up the unit starts to work. Does this mean the condensate overflow shut off device is bad? Or is there another problem?

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