Arkansas HVACR NewsMagazine March 2025

HVACR NewsMagazine March 2025

Tech News

In a real life application, this means that the red 24v power wire from the furnace is now connected to the White W terminal in the thermostat, which sends 24v power to the W terminal at the furnace control board. See the pic below. The 24v power on the W terminal means that the furnace must turn the heat sequence on. (This will start with the inducer motor turning on.)

Test #2 Heat Mode

Connect one alligator clip probe to the R red wire and the other probe's alligator clip to the W white wire. With the thermostat mode set to off and the fan set to auto, the multimeter should display 0.L.

Test #3 Air Conditioning (Cooling) Mode

Connect one alligator clip probe to the R red wire and the other probe's alligator clip to the Y yellow wire. With the thermostat mode set to off and the fan set to auto, the multimeter should display 0.L.

Now turn the thermostat to heating mode and adjust the temperature up above the ambient temp, using the thermostat face. The multimeter should now display 0.0Ω, signaling that R and W are now connected as seen in the pic below.

Now turn the thermostat to cooling mode and turn the temperature down below the ambient temp, using the thermostat face. The multimeter should now display 0.0Ω, signaling that R and Y are now connected as seen in the pic below. This may not happen