York Package Unit: PCG4

Re: Flashing Code 4

Code 4 = Limit Switch or Roll-Out Switch Open

► The automatic-reset primary Limit Switch and the manual-reset Roll-Out Switch are wired in series, so either limit open will generate a Code 4.

► NOTE: If the limit circuit remains open for more than 5 minutes, the control will switch to a Code 11. 

► NOTE: If the limit circuit remains open for more than 15 minutes, the control assumes that a Roll-Out Switch has tripped and will switch to a Code 5. 

CHECKOUT:

1. Check the Limit Circuit

• At the control board 9-pin plug, use a volt meter to check for 24VAC on each side of the limit circuit.
  • Check voltage between Pin#1 (Red/Grn 36) and "C".
  • Check voltage between Pin#5 (Red/Blk 35) and "C".
    • Power on One Side Only = Limit Circuit Open → Step 2. Check Limits
    • Power on Both Sides = Limit Circuit Closed ⇒ Reset the board by cycling power to the unit. 
      • Code 4 Returns + Limit Circuit Closed = Bad Control Board

2. Check Limits

• Check the Roll-Out Limit
  • The Roll-Out Limit is located on the plate above the burners.
  • With the wires attached to the limit switch, check for 24VAC from each side of the Roll-Out Limit to "C".
    • Power on One Side Only = Limit Circuit Open → Article: PCG4 Flashing Code 5
    • Power on Both Sides = Limit Circuit Closed ⇒ Check the Primary Limit (below)
• Check the Primary Limit
  • The Primary Limit is located inside the blower compartment and protrudes into the heat exchanger compartment.
  • With the wires attached to the limit switch, check for 24VAC from each side of the Limit Switch to "C".
    • Power on One Side Only = Limit Switch Open
      • Limit Switch Open + Hot Heat Chamber → Step 3. Check Blower
      • Limit Switch Open + Cool Heat Chamber = Bad Limit Switch
    • Power on Both Sides = Limit Switch Closed ⇒ Reset the board by cycling power to the unit. 
      • Code 4 Returns + Limit Circuit Closed = Bad Control Board

3. Check Blower

• During a Code 4 lockout, the indoor blower should be running continuously.
  • Code 4 + Blower Operating → Step 4. Check Temperature Rise 
  • Code 4 + No Blower Operation ⇒ Continue
• Make sure that both the High Voltage and Low Voltage plug are secure at the ECM blower motor.
• Check for 24VAC at the control board between "W SPD" and "24V COM".
  • ​​​​​​​Power Present + No Blower = Bad Blower Motor
  • No Power Present = Bad Control Board

4. Check Temperature Rise

• Reset the control if necessary by cycling power to the unit.
• Start the unit in a heat cycle.
• Check the return air temperature in the blower door (don't assume that the house temperature = the return temperature).
• Check the supply air temperature either in the ductwork near the unit or at a close supply vent.
  • Temperature Rise = Supply Air Temperature - Return Air Temperature
• Compare the Actual Temperature Rise to the unit's Rated Temperature Rise (typically 40 - 70 deg).
  • ​​​​​​​Temperature Rise More than 70 deg → Step 5. Check Air Filter
  • Temperture Rise Less than deg + Code 4 ⇒ Suspect a Bad Limit Switch

5. Check Air Filter

• Remove and inspect the air filter.
• Recheck the temperature rise with the filter removed.
  • ​​​​​​​Temperature Rise Still High → Step 6. Check Gas Pressure
  • Temperature Rise Drops to Normal Range = Restricted Air Filter

6. Check Gas Pressure

• Shut-off the unit by removing a call for "W".
• Hook a gas pressure gauge to the outlet or "manifold" side of the gas valve.
• Start a call for Heat and monitor the gas pressure when the unit fires.
  • Natural Gas = 2.5" w.c. minimum to 3.5" w.c. maximum
  • LP Gas = 9" w.c. minimum to 11" w.c. maximum
    • Pressure Below Maximum + High Temperature Rise → Step 7. Check Blower Speed
    • Pressure Above Maximum ⇒ Adjust Gas Pressure & Re-check Temperature Rise

7. Check Blower Speed

• Shut-off the unit by removing a call for "W".
• After the blower shuts off, remove high voltage power by pulling the service disconnect or turning the breaker off.
• Check the Low Voltage plug at the ECM blower motor to see what speed the unit is using for Heat.
  • ​​​​​​​The White wire will be connected to one of the Low Voltage terminals of the motor (1=Low to 5=High).
  • If possible, move the White wire to a higher speed.
• ​​​​​​​Re-apply power to the unit and energize a call for Heat.
• Re-check the temperature rise.​​​​​​​