Ameristar Gas Furnace: A951X

Re: Flashing E3_2

E3_2 = Furnace Pressure Switch failed to close on a call for heat.

• There are 2 Pressure Switches - one connected to the inducer and one connected to the drain line.
• The Pressure Switch connected to the inducer is the only one that will cause the E3_2 code.

CHECKOUT:

1. Check Control Board

• Start the furnace with a call for heat.
• Ensure that power is present on "W" by checking for 24VAC between "W" and "C".
  • No Power = No Call for Heat
  • Power = The Inducer motor should start within 15 seconds.
    • Inducer Motor Starts → Step 2. Check Inducer
    • Inducer Motor Does Not Start + E3_2 ⇒ Check for 115V power to inducer.
      • Power + No Inducer → Step 2. Check Inducer
      • No Power = Bad Control Board

2. Check Inducer

• Observe and listen to the inducer motor.
  • Inducer motor runs normally → Step 3. Check Pressure Switch
  • Inducer motor hums but does not start = Bad Inducer Motor/Capacitor or Item in Inducer ⇒ Remove inducer & check
  • Sound of Water "Slurshing" = Water in Inducer ⇒ Remove Inducer, pour out water, re-install inducer ⇒ Check Condensate Drainage
• Listen for the sound of air sucking around the seal where the inducer assembly attaches to the heat exchanger.
  • May need to tighten mounting screws to improve seal.
• Listen for sounds of water in the vent piping (near the furnace and at the vent termination).
  • If water is gurgling in the vent, look for sags or low spots in the vent piping that will hold water.
    • The vent piping must have a constant slope back toward the furnace.

3. Check Pressure Switch

• Make sure there are no sags in the pressure switch hoses that could hold water.
• Start the furnace with a call for heat.
• ​​​​Check Vent Switch (Connected to the Inducer)
  • Switch Contacts
    • At the Pressure Switch
    • With the wires attached to the switch, check for 24VAC between each terminal of the Pressure Switch and Common (YL/3 and OR/11)
      • 24VAC On Both Sides = Switch Closed 
      • 24VAC On One Side Only = Open Switch ⇒ Use a pressure meter to check the Switch Pressure (below).
    • At the Control Board
    • At the 10-Pin Plug of the Furnace Control Board, check for 24VAC between Terminal#3 OR/11 and Common.
    • Then check for 24VAC between Terminal#9 YL/3 and Common.
      • 24VAC On Both Sides = Switch Closed 
      • 24VAC On One Side Only = Open Switch ⇒ Use a pressure meter to check the Switch Pressure (below).
  • Switch Pressure
  • Remove the Pressure Switch hose from the Inducer Motor.
  • Inspect the pressure switch hose for a:
    • Loose hose
    • Dry-rotted, cracked hose
    • Clogged hose
  • Inspect the port on the inducer motor for any clog or restriction.
  • Connect a pressure meter to the Inducer Motor pressure port.
  • Compare actual pressure to the pressure rating on the switch.
    • Pressure Near or Below Rating = Clogged or Restricted Vent
    • Pressure Well Above the Rating + Open Switch = Bad Switch or Water in Switch