furnace pressure swich

mburg

a furnace wasn't igniting the error code said the pressure switch, I cycled the power and it is working now, should I still change the switch? also the switch has two hoses going to it the top hose goes to the gas valve and burner box, the bottom one connects into the inducer. I measured the pressure at each hose the top one was -.55 and the bottom one was -3.39. what is the purpose of having two and how does that pressure switch operate? also when the unit was running I disconnected the top one and it continued to run when I disconnect the bottom one that shut it down.

don_9

The line that goes to the burner box,gas valve n pressure switch is called a reference tube.it controls firing rate according to changing negative pressure within the burner box.the other one that goes directly to the inducer from the pressure switch is incase the inducer goes bad or a blockage in your vent piping.It keep the furnace from firing.Other things to look for are blocked drain,cracked heat exchanger,vent pipe not size correctly.

don_9

Let me add one more thing here.i know nordyne products will give a pressure switch fault code if there a slight voltage drop thru any safetys.i had acouple this winter that kept showing a pressure switch code and it was other safety switches that were the cause.

unclejohn

I would replace that old metal switch.

mburg

It was a plugged condensate drain

unclejohn

You should have heard the water swishing around when you cycle it on.