carrier 90% furnace

[pshad124]

Im having trouble figuring out why this 6 year old furnace wont close the pressure switch?

[OldSchoolMech]

Is it stuck open?
Is the venter motor working?

[pshad124]

the venter motor is working and I have replaced the pressure switch

[pshad124]

It seems to have to much negative pressure acording to out digital magnehelic guage. we taken off both the flue and freshair intalke and no change

[pshad124]

Ive replaced the pressure switch and cannot get the furnace to close the pressure switch. any ideas? ive removed the flue and fresh air intake and it did not change any thing.

[joeblo]

Check the vacuum to the switch, maybe the line is plugged up or there is water in furnace due to a plugged drain.

[pshad124]

Check the vacuum to the switch, maybe the line is plugged up or there is water in furnace due to a plugged drain.

Checked all of that and thats not it. this is a very unusual situation and hard to figure out. Not a typical trouble call!

[dsprice]

Believe it or not, the furnace drain can cause this! The corrugated hoses have to be switched based on left or right flow. They are tagged different colors with description on the panel.

[jetstream]

Those corrugated hoses also can crack, and it can be difficult to spot. Be sure to check them.

[rchristie420]

pressure swith could be DOA

[Joehvac25]

What's your pressure compared to the switch? Is it a differential ps?

[remtre5]

The first thing is how much vacuum the furnace pulls with the intake and exhaust off. The drain could cause this problem. The secondary could be plugged, but this normally trips the roll out. make sure the black intake box under the burners is not plugged with a bird nest etc.

[Andr00]

My bet is that there's a gallon of water in the secondary. Good old Carrier drain traps. I have days where I un-clog 3-4 of those in a row.

Pull the flex hose off the top of the drain trap.