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  1. #1
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    Bryant Furnace problems

    About two weeks ago the furnace shut off before the house had warmed up. Error code 31 was flashing indicating an air flow problem or pressure switch glitch so I removed, cleaned and vacuumed the stack, installed a new filter, cleaned out the condensate and overflow line, and reset the limit switch. When I called for heat at the thermostat, I noticed that the red light indicating the thermostat was activated was not lit. I had to jump the red and white wires at the control panel to activate the furnace. When I did that, the inducer motor kicked in, the burners ignited and the blower fired up. It heated normally for about 6 minutes before the limit switch tripped and again flashed code 31. Volts across each terminal on the pressure switch run about 25v - 26v. The high temp limit switch opens and closes normally. The hose on the pressure switch is not plugged, however, when I suck on the end of the hose activating the diaphragm in the switch I notice that it will not hold a vacuum. Not sure that it is supposed to. At this point I am kind of stumped. Is it the thermostat, the control board or the pressure switch?
    Anyone have any thoughts on this I'd be happy to listen. - Jeff

  2. #2
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    Quote Originally Posted by jeff49 View Post
    About two weeks ago the furnace shut off before the house had warmed up. Error code 31 was flashing indicating an air flow problem or pressure switch glitch so I removed, cleaned and vacuumed the stack, installed a new filter, cleaned out the condensate and overflow line, and reset the limit switch. When I called for heat at the thermostat, I noticed that the red light indicating the thermostat was activated was not lit. I had to jump the red and white wires at the control panel to activate the furnace. When I did that, the inducer motor kicked in, the burners ignited and the blower fired up. It heated normally for about 6 minutes before the limit switch tripped and again flashed code 31. Volts across each terminal on the pressure switch run about 25v - 26v. The high temp limit switch opens and closes normally. The hose on the pressure switch is not plugged, however, when I suck on the end of the hose activating the diaphragm in the switch I notice that it will not hold a vacuum. Not sure that it is supposed to. At this point I am kind of stumped. Is it the thermostat, the control board or the pressure switch?
    Anyone have any thoughts on this I'd be happy to listen. - Jeff
    You are indicating different problems here. The thermostat is just a switch, so if you turned up the stat and no start, but jumped the red and white post at the furnace and it started and keep going for 6 min. this could be too much
    voltage drop in the stat circuit. . You have 24 or more volts going out the red wire to the stat check and see what voltage you have coming back on the white wire at the furnace. When checking the 24 volts any where use the c,common post for one lead on your tester. Common to white from stat, when testing pressure switch do the same thing common to one side of switch and then the other. On your pressure switch take the hose off an make sure there is no water in that line. Inspect the hose real close for cracks. a very small crack can stop your furnace. Did you check out your stacks out side for any blockage? So make sure you are testing right and check out all this and get back with me. Later Paul

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    jeff49 (11-14-2010)

  4. #3
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    Thanks for responding Paul.
    I have 26 volts going out the red wire at the furnace and 0 volts coming back on the white wire. Each side of the pressure switch has 26 volts. There is no water in the pressure switch hose and it has no leaks in it, however,the diaphram inside the switch does not hold a vacuum. I removed the vent stack from the furnace and checked it for obstructions - it was clean. While I had it disassembled, I started the inducer motor to ensure it was operating properly, and it was. The high temp limit switch is functioning normally.
    When I jump the red and white wires at the furnace, it ignites normally and runs for about 5-6 before a limit switch mounted up on the side of the inducer motor outlet trips and generates a code 31. I'm thinking, as you said, that I have two issues. One with the stat/control panel and possibly one with the pressure switch.
    Thanks for your help on this.
    Jeff

  5. #4
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    Quote Originally Posted by jeff49 View Post
    Thanks for responding Paul.
    I have 26 volts going out the red wire at the furnace and 0 volts coming back on the white wire. Each side of the pressure switch has 26 volts. There is no water in the pressure switch hose and it has no leaks in it, however,the diaphram inside the switch does not hold a vacuum. I removed the vent stack from the furnace and checked it for obstructions - it was clean. While I had it disassembled, I started the inducer motor to ensure it was operating properly, and it was. The high temp limit switch is functioning normally.
    When I jump the red and white wires at the furnace, it ignites normally and runs for about 5-6 before a limit switch mounted up on the side of the inducer motor outlet trips and generates a code 31. I'm thinking, as you said, that I have two issues. One with the stat/control panel and possibly one with the pressure switch.
    Thanks for your help on this.
    Jeff
    One other thing to check is , make sure your inducer fan bolts are tight. I have seen them get lose and cause a air leak. If this is the pressure switch and you want to check it, make your self a jumper wire and after the furnace is fired , jump the pressure and see if it keeps going.
    Later Paul

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    jeff49 (11-14-2010)

  7. #5
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    Thanks Paul:
    Yep, the inducer bolts are all tight with no apparent leaks. I jumped across the pressure switch after the furnace fired up and it kept running.
    Thanks again for your assistance.
    Jeff

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