The furnace blower started running constantly and I noticed there was cold air coming fromm the vents and not heat. I have a Payne (Carrier) furnace. The spark gap igniter was not throwing a spark to initiate the pilot. Wondering if the ingniter has gone bad or if it is not getting the electricity to initiate the spark? It went from working one day to not working the next. It's an older furnace. Is there a way to check if the igniter is getting electricity or should the igniter just be replaced?

  • Can you post the model of the furnace? Feb 2, 2016 at 1:35
  • The model number is 394GAW000100
    – M-R
    Feb 3, 2016 at 21:44
  • Can you post a wiring diagram for the furnace? Feb 3, 2016 at 23:16

1 Answer 1


If the blower is running nonstop, then there's likely a open limit (probably high limit).

If this is a high efficiency unit, and the draft inducer is running continuously before the unit shuts down (lockout). It's likely a problem with the exhaust piping, or a bad pressure switch.

Without knowing exactly what's happening, it's difficult to explain how to troubleshoot.

  • The blower running constantly was what triggered me to take a look at what was happening. There was no flame in the furnace while the blower was on. There is an electrical switch on the furnace, which I shut off, and that stopped the blower. Even when I have the thermostat turned off but flip the switch on the furnace to on, the blower kicks on. I turned the thermostat on to call for heat, but the igniter was not/is not throwing a spark to light the pilot.
    – M-R
    Feb 3, 2016 at 21:51
  • @M-R The switch on the furnace is called a servicemen switch, and it's used to shut power off to the furnace. If the blower runs whenever the furnace has power, it means the limit circuit is open. That could be a high limit, rollout, or other protective device that has detected a problem. You'll have to determine which limit is open, and replace/reset it. If it continues to open, you'll have to figure out why and fix the problem.
    – Tester101
    Feb 3, 2016 at 23:41
  • It appears that there is just the one limit circuit switch. The part Number is HH12ZA251C L250 8650. I did a search on HH12ZA251C, but was not coming up with a direct match. The manufacture on this switch is STEMCO. Do you know if there are alternative part numbers that would work for the unit?
    – M-R
    Feb 8, 2016 at 2:05
  • @M-R I'm not a parts expert. I'd start by connecting the manufacturer.
    – Tester101
    Feb 8, 2016 at 2:29
  • Thanks, your information has been helpful in pointing me toward what I need to look into and research.
    – M-R
    Feb 8, 2016 at 5:02

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