Trane Package Unit: 4WCX

Re: Blows Heat in Cooling Mode

The customer reports that the thermostat was set for cooling, but the unit was blowing hot air.

CHECKOUT:

1. Check Operation

• Set the thermostat to call for cooling.
• Check the temperature drop through the unit.
  • Unit Cooling → Step 4. Check Reversing Valve
  • Unit Blowing Heat → Step 2. Check Low Voltage

2. Check Low Voltage 

• Check for 24VAC power between "W" (White) and "B" (Blue) on the thermostat connections.
  • Power Present = Call for Electric Heat → Step 3. Check Thermostat
  • No Power ⇒ Continue
• Check for 24VAC power between "O" (Orange) and "B" (Blue) on the thermostat connections.
  • No Power = No Call for Cooling → Step 3. Check Thermostat
  • Power Present ⇒ Continue.

3. Check Thermostat

• Make sure the thermostat is set correctly.
• Cycle through the thermostat "System" settings and make sure there is a setting for "EM HEAT".
  • No "EM HEAT" = Mis-Configured Thermostat
  • "EM HEAT" Present ⇒ Continue
• Unit Not Receiving "O"
  • Remove the thermostat from the subbase.
  • Make sure that the Orange wire is attached to the "O" terminal.
  • Temporarily connect "O" to "R" and recheck voltage between "O" and "B" at the unit.
    • No Power = Broken Wiring
    • Power Present = Bad Thermostat
• Unit Receiving "W"
  • Remove the thermostat from the subbase.
  • Make sure the White wire is connected to "Aux".
    • Honeywell T6 Pro ⇔ Connecting the "White" to "W" instead of "Aux" will cause the electric heat to run continuous.
  • Disconnect the White wire from the subbase.
  • Restart the unit in Cooling.
  • Recheck for 24VAC between "W" and "B" at the unit.
    • ​​​​​​​No Power = Bad Thermostat
    • Power Present = Shorted Thermostat Wiring​​​​​​​

4. Check Reversing Valve

• At the Reversing Valve:
  • ​​​​​​​​​​​​​​Check the operating position by seeing which "Large" line is hot.
    • ​​​​​​​Line to Condenser Hot = Cooling Mode → Step 5. Check Heaters
    • Line to Evaporator Hot = Heating Mode ⇒ Continue
  • ​​​​​​​Check to make sure the solenoid is properly attached to the valve.
  • Make sure the low voltage connections are securely attached to the solenoid.
  • Check for 24VAC across the low voltage connection of the solenoid.
    • ​​​​​​​Power Present = Bad Reversing Valve
    • No Power Present ⇒ Check wiring between Defrost Control and Solenoid
      • ​​​​​​​Wiring OK = Bad Defrost Control

​​​​​​​​​​​​​​​​​​​​​​​​​​​​5. Check Heaters

• Check the heater contactors and make sure none are engaged.
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