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Thepugguy · Oct 21, 2011, 01:03 PM

Bryant plus 355MAV, Furnace runs a few seconds then stops, pressure switch calibration fault code, 4 yellow 3 green. I checked the intake and exhaust pipes, seem clear... don't know what to do from here without screwing something up.

T-Top · Oct 21, 2011, 03:12 PM

Check your condensate drain this system produces water while it runs. If the drain is restricted the pressure switch will not close.

Thepugguy · Oct 21, 2011, 03:27 PM

Thanks,. which one is that?.

T-Top · Oct 21, 2011, 03:57 PM

You should have a small white box in the blower section with 3 rubber lines going to it. It will exit the furnace with one line, PVC. You need to check for restriction in rubber hoses and pvc that exits the furnace. The rubber hoses need to be in good shape with out any cracks or breaks in them. You also have a plastic screen where the white 2" plastic pipe goes into the burner box(its fresh air intake) It does not take much to restrict and keep the pressure switch from closing.

Thepugguy · Oct 21, 2011, 05:11 PM

Thanks for your help,. greatly appreciated... do I take the metal plate off the burner box with the round window in it? To get at this screen?. I tried taking the pvc intake pipe out but not enough room to pus it out to look inside,. I washed the condensate drain box,. very full of crap and one of the lines was completely clogged,. put all back together and it still reads the same error,. I didn't hook up the drain lines outside the furnace,. I don't think that would matter?. its not a vacume is it... they were full of crap to,. and want to replace before hooking up again... Is there anything else I can try before calling in the pro?

T-Top · Oct 21, 2011, 05:25 PM

If you had junk in the rubber line it may be restricted at the collector box or inducer housing. You may have to blow lightly back towards the furnace on the two larger lines to help remove restrictions. The smaller line goes to the pressure switch and no water should be in their. As far as the intake pipe screen the pipe or the black housing under the burner box will have to be removed to gain access. I think only 2 screws in the front holds the fresh air box in place.(black box that the pvc goes in to)

Thepugguy · Oct 21, 2011, 06:19 PM

OK,. I blew back on the 2 larger lines,. I tried to get the intake box off, but it's right above the gas line/box thing,. and removing the two screws didn't let me take it of or even move it,. well it sounds the same,. im obviously not educated HVAC but the furnace sounds like its going to go after it starts up like its going to go,. then shuts down... I don't know what's left?

T-Top · Oct 21, 2011, 06:51 PM

Ok after going back and reading the 1st post I realized the code you are giving is 43 low pressure switch open in high fire. For some reason I was thinking 350mav(1 stage furnace) not 355mav(2 stage furnace). The code you are looking at could actually be code 34 flame sensor fault. It hard to keep all models straight. Just for kicks pull the flame sensor out clean or scrape with a knife and reinstall. The flame sensor is a metal rod that sets in front for the burners opposite side of the ignitor, one wire going to it and one screw holds it in place on the bottom of the burner box.

Thepugguy · Oct 21, 2011, 08:01 PM

Thanks T,. I haven't done that yet,. while I was waiting I took the hose off that connects the two switches.. I saw a droplet off water,. I blew through the hose in and out on each switch, I heard what I thought was some gurgaling in one of them,. the one that the air went both was easily,. the other would go through or back,. then re connected. Started up the furnace and it ran and fired up,. then shut off after about five min.'s... and the code changed to 3 yellow and one green,. but left it on and it kicked in again and has stayed on,. don't know why,. and I'm wondering if I should get new switches or it should be OK,. I don't know,. dont want to leavwe it until I really need it,. im going to re clean.. rinse everything again... anyway... but what do you think..