My Trane XB90 model TUC060C936BA natural gas furnace will run without any apparent problems for its first cycle after being off for a while (several hours/overnight). From my non-expert understanding, the draft inducer comes on, then there is a yellow glow where the flame will soon be, followed by the gas firing and the fan starting. It will then stay on until the thermostat reaches the temperature it is set to. At which point it will rest until the house temp drops enough to be time to start again. All good.

However, once it is time to start again something is going wrong. I think the draft inducer is still starting and will run for a little (less than a minute) and then there is some clicking and the draft inducer stops. It will repeat this process until I give up and turn the thermostat off and wait for a few hours. I don't see any orange or yellow glow, it doesn't fire, and it does give a pressure switch error code. I put a new filter in. While I cannot see inside the exhaust pipe, there is no clog at the end of the pipe and it is screened and has air coming out. There doesn't seem to be any problem in the condensation line either.

Video of the first cycle working

Video of the second cycle attempt (not working)

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    What model furnace? Are there any error lights on the control board? If you have to remove a cover and the power goes out look for a plunger switch that the cover pushes in on. These normally have an over ride position for maintenance, pull out and it will turn the power back on but remember everything is live now. – Ed Beal Dec 11 '20 at 16:17
  • Yes, what make/model is this furnace? – ThreePhaseEel Dec 12 '20 at 3:18
  • Sorry I should have included that originally: – jr7001 Dec 12 '20 at 19:25
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    It says Trane XB90 on the front and model: TUC060C936BA serial: 34732M07G – jr7001 Dec 12 '20 at 19:32

Sounds like it's failing the inducer motor pressure test sometimes which is the first test. Sometimes the fitting where the hose from the pressure switch in clogged with debris and needs cleaned and sometimes the inducer housing fills with water because of a condensate drain obstruction or pump issue.

  • Thank you, Jim. I was thinking something along those lines, too. I checked the hose and the condensate drain and didn't see anything that seemed off. Is there a reason it consistently passes the pressure check for the first cycle? If it was really clogged, wouldn't it fail the first time, too? – jr7001 Dec 14 '20 at 17:21

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