Knowledgebase

PUDD - No Heat / Won't Come On

Article ID: 368
Last updated: 10 Apr, 2020

York Gas Furnaces: PUDD

Re: No Heat / Won't Come On

This condition is generally reported two different ways by the customer:

  1. "The furnace won't do anything." - Indicating that there is no activity from the furnace on a call for heat.
  2. "The furnace makes a noise, but it never blows-out hot air." - Indicating that the inducer motor runs, but ignition never takes place.


Qty Possible Causes:
1 Bad Glow Plug
2 Pressure Switch Fault
No Power (Door Switch)
Ignition Control Locked-Out
Bad Inducer Fan
Bad Ignition Control
Bad Thermostat (Thermostat not calling)


CHECKOUT:

1. Check Power

  • Check for 24VAC between "R" and "C" on the transformer terminal block.
    • No Power ⇒ Check Blower Door Switch and High Voltage Power to Furnace
    • High Voltage but no Low Voltage ⇒ Check transformer.
  • Set thermostat to call for Heat
  • Check 24VAC between "W" and "C" on the transformer terminal block.
    • No Power = No Heat Call, Check Thermostat
    • Power & No Inducer = Bad Inducer or Bad Heat Relay
  • Inducer Running --> Check for 24VAC between "TH" or "24V" on ignition control ad "C" on the terminal block.

2. Check Safeties

  • 1LP Pressure Switch (3-wire)
    • Check for 24VAC between "C" on the pressure switch (Red) & "C" on the terminal block.
      • No Power = Bad Heat Relay
    • Check for 24VAC between "NO" on the pressure switch (Yel) and "C" on the terminal block.
      • No Power = Pressure Switch Not Closed
  • 2LP Pressure Switch (2-wire)
    • Check for 24VAC between "C" on the pressure switch (Yel) & "C" on the terminal block.
      • No Power = 1LP Switch Not Closed
    • Check for 24VAC between "NC" on the pressure switch (Brn) and "C" on the terminal block.
      • No Power = Pressure Switch Open
  • Primary Limit
    • Check for 24VAC between the (Blk) wire of the limit to "C" on the terminal block.
      • No Power = Blown Fusible Link (Mounted in the burner compartment)
    • Check for 24VAC between the (Brn) wire of the limit to "C" on the terminal block.
      • No Power = Open Limit

3. Check Ignition Control

  • Look for a flashing lockout light on the control.
    • Flashing Light = Lockout ⇒ Reset power and retry.
  • Glow plug should begin glowing within 30 seconds of receiving power on "TH" or "24V".
  • Gas Valve should energize within 60 seconds of powering the glow plug.

4. Check Glow Plug

  • Look for any visual cracks.
  • Use a meter to test resistance of glow plug.
    • No resistance = Bad Glow Plug
  • Check for 120V power to the Glow Plug during an ignition sequence.
    • No Power = Bad Ignition Control
    • Power present but no glow = Bad Glow Plug
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Article ID: 368
Last updated: 10 Apr, 2020
Revision: 10
Views: 26
Comments: 0