York Rooftop Unit: Predator DH, DM

Re: Ignition Control - Flashing Code 3

Flashing Code 3 = Inducer Pressure Switch failed to close or Tripped Roll-out.

The vent pressure switch and flame roll-out switch are wired in series. Therefore either switch open on a call for heat will generate a code 3.

CHECKOUT:

1. Check Control Board/Inducer

• Start the furnace with a call for heat.
  • The Inducer motor should start within 15 seconds.
    • Inducer motor hums but does not start = Bad Inducer Motor or Item in Inducer ⇒ Remove inducer assembly & check for obstruction.
    • Inducer motor does not attempt to start & shows Code 3 ⇒ Check for 230VAC power to inducer.
      • Power + No Inducer = Bad Inducer Motor
      • No Power = Bad Control Board
    • Inducer motor starts and runs normally → Step 2. Check Pressure Switch

2. Check Pressure Switch

• Ensure that the inducer is running.
• Remove the two Violet wires from the pressure switch.
• Check continuity between the two pressure switch terminals.
  • Continuity (Beeps) → Step 3. Check Rollout Switch
  • No Continuity ⇒ Continue
• Check the integrity of the pressure switch hose (they tend to dry-rot).
• Use a pressure gauge to check the negative pressure at the inducer connection (Minimum = -.5" w.c.).
  • High Negative Pressure + Open Switch = Bad Pressure Switch
  • Low Negative Pressure ⇒ Continue
• Check for blockage at pressure port.
• Check inducer blower wheel for damage.

3. Check Rollout Switch

• Press the reset button in the middle of the rollout switch.
  • Clicks = Rollout was Tripped ⇒ Reconnect all wires, make sure Code 3 goes away and check for a Bad Heat Exchanger
  • Doesn't Click ⇒ Continue
• At the Heat Control Board, Check for 24VAC between "W1' and "C".
• Check for 24VAC between "PS" and "C".
  • Power on "W1" + No Power on "PS" = Open Circuit ⇒ Recheck both switches.
  • Power on "W1" + Power on "PS" + Code 3 = Bad Control Board