Bryant Plus 90 Burners kicking on then off

[paul52446m]

I would really appreciate any thoughts or guidance on an ongoing problem with my Bryant Plus 90 High Efficiency gas furnace (Model 35MAV036080, S/N 0397A00985, installed 3/13/97 in Washington DC metro area).

In addition to regular maintenance by the company that installed it, I’ve had two service contract visits from their staff recently, for a problem that we can’t seem to resolve: The furnace will start the first phase, where it sounds like it’s drawing air in, but never goes any further. It just shuts off until the next time it tries, with the same effect, and will try sporadically throughout the day if I don’t turn off the thermostat.

On the first visit, a code 31, “Pressure Switch will not close or respond,” per the owner’s manual, was noted by the technician. Per the invoice, “checked pressure switch and found intake hose was cracked. Repaired hose and ran unit, everything seems to be working good now” and it was operational again.

A day later, the error code was back – then disappeared for a few days, only to return permanently.

On the second visit, the (different) tech that came, after checking the outside vent for blockage (none), noted on the invoice that the “secondary heat exchanger trap clogged – pulled trap hoses – drain secondary heat exchanger – cleaned trap – reinstalled – start system. Cycled several times OK.”

That was last night, and now the unit is offline again, with the same code 31 flashing on the LED indicator.

I’ve read this thread carefully, and am wondering if the symptoms might related to what was described in post #18 of this thread (haven't been able to find any more recent threads on this topic.)

However, any thoughts at all would be greatly, greatly appreciated, with the understanding that you aren’t onsite.



Thank you!

Hi Paul here. There is a black plastic cover over the secondary heat ex changer. It about 4'' tall 18" long or so. depending on furnace size and maybe 2" deep. If you take this cover off you will see all these small tubes with swirl
baffles in them. They used too much caulk in there and this caulk can be reducing the air flow to the inducer so pressure switch will not make. You need to clean out the excess caulk , pull the baffles and make sure they are clean. This can also be holding back water so it does not drain right. Paul

[marasca]

Thank you

Thanks for the quick response, Paul - that's great information, and I will check it out right now.

Sincerely,

Graham