4YCY - Flashing Code 3

Trane Package Unit: 4YCY

Re: Flashing Code 3

Code 3 = Pressure Switch Fault

A Code 3 will be generated in either of the following conditions:

• The pressure switch failed to close with the inducer motor energized.
• The pressure switch failed to re-open (stuck closed) with the inducer motor de-energized.

CHECKOUT:

1. Check Controller

• Activate a call for heat from the thermostat (confirm 24VAC between "W" and "C")
  • No Inducer Fan + Code 3 → Step 2. Check Inducer Motor
  • Inducer Fan Starts + Code 3 after several seconds → Step 3. Check Pressure Switch Contacts

2. Check Inducer Motor

• With "W' energized, check for 230VAC power between the IGN "Inducer HI" 23A (BK) and CC1 1C (RD).
• Check for 230VAC power between the IGN "Inducer LO" 21A (BL) and CC1 1C (RD).
  • No Power = Pressure Switch Stuck Closed or Bad Control Board → Step 3. Check Pressure Switch
  • Power + No Fan = Bad Inducer Motor or Capacitor

3. Check Pressure Switch 

• Ensure that the pressure switch hose is attached at the inducer pressure port and the pressure switch.
• Contacts
• With "W" energized:
• Check for 24VAC between both sides of the pressure switch and Gnd.
  • Power on Both Sides = Switch Closed 
  • Power on One Side Only = Switch Open
    • Switch Open + No Power to Inducer = Bad Control Board
    • Inducer Off + Switch Closed = Bad Pressure Switch
• Pressure
• With the inducer running, use a pressure gauge to check the inducer negative pressure.
  • Pressure Above Switch Rating + Open Switch = Bad Pressure Switch
  • Pressure Below Switch Rating = Clogged Pressure Port or Restricted Inducer Fan

4. ADPS Switch Setting

• The ADPS switch will sometimes fail to re-open when set for the lowest setting.