Troubleshooting Tip: How to create a bypass so your fan will run

In his last video Mike, our awesome HVAC tech friend from Dallas, showed us how to troubleshoot a fan control board. Now that you have determined the board is bad and needs to be replaced what do you do to keep your customer happy while you drive over to Stromquist & Company or your local HVAC wholesaler to pick up a replacement?
Well if it is heating season get your customer a jacket because the trick Mike is about to teach you is only safe for cooling. As you can see

Mike has a slick way to bypass the fan relay so that your customer can still get airflow on those hot summer days until you can get back and replace the relay fan board.

Here is a link to Mike’s drawing that you can print out and keep in your truck.

Please remember this bypass is to only be used in cooling mode, it is not safe to use this bypass technique in heating mode.

Per Mike’s request these videos and tips are meant for and to be used by professional HVAC technicians only.

Thanks Mike.


5 Responses

  1. Thanks for the kind words John Paul ! Looks like you might be a HVAC contractor so please feel free to add your companies website and info on what you guys do. Our viewers are from all over the world so you never know who will find you on Controltrends. Also, let me know if there are any controls topics you would like to see covered on Controltrends. Again, thanks for your kind comments. Eric

  2. A really good idea when the board has failed and you want to leave the customer happy. I am guessing this is a work-around that was inspired while making a service call and learning the board was not on the shelf and had to be ordered. Tip of the hat for this video and information.
    HVAC Basics


  3. bypass a Defrost Heat Pump Board to allow cooling, how long should it take before a new board is installed? Does it even matter how long it takes?

  4. What are the risks of bypassing Defrost Board, if any? How long can bypass be active, with no negative effects?

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