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My inducer motor bearing was making a ton of noise and likely about to go out so I replaced it. After installing the new inducer motor my furnace will run for 20 to 30 minutes and then throw a pressure switch stuck open error. I tested the pressure switch and it seemed fine; however, since they are relatively inexpensive I replaced it to be sure. The furnace is still throwing the pressure switch error. Everything I've read indicates if there is a problem with the inducer motor or how much air it's moving and/or the pressure switch is actually faulty the furnace will not turn on at all. I haven't been able to find any info where the furnace will run for a significant amount of time and then throw the error. Could it be the board?

Note: Before replacing the inducer motor the furnace ran without issue...it was just really loud.

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  • Have you tried putting the old motor back in to see if normal (but loud) function resumes?
    – FreeMan
    Feb 25 at 16:37
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    Good question. I have not. I don't remember off hand if I kept the old motor. If I did I will definitely try that... Feb 25 at 17:41
  • Re-seat the wiring harness. Perhaps inducer is still running when it's checking to see that every thing is off between cycles. So like, in a half hour it trips on over heat and tries to start a new cycle but inducer is running so it 'looks' stuck open.
    – Mazura
    Feb 25 at 18:53
  • 30 min is a pretty long call for heat. Does it trip out w/o the filter in place and the door off the chamber? (give it as much air as possible) On some units an overheat will leave the inducer running, and the first 3(?) overheats won't throw an error.
    – Mazura
    Feb 25 at 18:58
  • We drop our house down pretty cool at night and it can take 30 mins to 1 1/2 hours to heat to daytime temp. The furnace turns on and we get heat for the 20 to 30 mins it will run and then it just throws the pressure switch error. I'll try re-seating the harness. Thanks. Feb 26 at 0:05

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I would add below as a comment, but I don’t have enough reputation points to do so. If moderator, such as @BMitch, would move this to comments I think this will help OP, and would appreciate it.

Unless I’m missing something, looking for air flow problems related to the blower motor is a waste of time. The inducer air circuit should be independent of the blower air circuit (unless the heat exchanger is compromised in which case you have a much bigger problem and this should trigger a flame rollout or other trouble code).

Any increased (or decreased) airflow from the blower should have zero effect on the vacuum created by the inducer.

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