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My son-in-law's Goodman B1809913S control board only has R, W and G terminals (no Y terminal). In order to make the AC compressor AND the furnace fan operate the Y and the G wires are jumpered together at the furnace end of the thermostat cable. In this configuration there is no way to control the fan independently of the AC compressor. Currently when the fan is set to "Manual" at the thermostat the AC compressor AND the fan run continuously. Not a good situation because it would cause the AC compressor to run continuously.

Is there a way to wire or configure the system that would allow the fan to run continuously without turning on the AC compressor?

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    Hello, and welcome to Home Improvement. When you say "furnace fan" do you mean the main air-handling fan? And, you should probably take our tour so you'll know how best to participate here.
    – Daniel Griscom
    Jul 8, 2019 at 14:04
  • That Y wire that the G is jumpered to has to go back to the compressor somewhere, somehow. Instead of being jumpered to the green, it needs to go to the thermostat. Are there any extra wires that are unused at the thermostat?
    – JPhi1618
    Jul 8, 2019 at 14:38
  • Did you ever get this resolved? If so, please give a check-mark to the answer provided, or write up your own answer explaining what you did to get it fixed and give yourself a check mark. That will help others with this kind of problem know that this has a resolution and is a good place to look for their answer.
    – FreeMan
    Aug 2, 2020 at 17:50
  • The issue has been resolved. My son-in-law was gifted one of those smart thermostats which replaced the mechanical thermostat. He had a local AC company to the install. All works well now. Thank you.
    – BAH911
    Aug 3, 2020 at 21:13
  • @BAH911 -- post that as an answer and I'll give you a +1 for it
    – ThreePhaseEel
    Aug 3, 2020 at 22:36

1 Answer 1

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Use a relay

You can wire a standard HVAC "blower relay" of the SPST-N/O type with its coil connected between Y and C and its contact connected between G and R and mount it in the furnace's wiring compartment. This allows the thermostat to energize G by itself to turn on the blower without energizing Y by accident, but also energizes G to turn the fan on when the thermostat applies power to Y to call for compressor.

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