Coleman Evcon Model as36a264t LM

Hi I have the above model forced natural gas furnace. I started getting the three blinking lights indicating the pressure switch failed to close. I am not sure what to do. I removed the rubber hose and mde sure nothing was stuck in it and blew through it (hose only, did not blow into furnace parts). The hose itself is not clogged.

A little background. The furnace has never failed but I noticed something was off in my furnace closet. The drain valve itself was tilted where it would not drain water correctly. Not sure how or who tilted it up, but it was. When I laid it back down the water in the drain valve ran out into the drain. I figured this was a little common sense. As for now, The water has been drained for a couple of hours without me tinkering with anything.

Any suggestions would be appreciated aside from telling me to call a tech. Its just starting to get cold in Indiana and I am more broke than the furnace. Though, the longer the furnace doesn't work, the lower my gas bill :)


Thank you.

Sounds like you need to blow lightly into the pressure switch. If it or just tap it and see if it shuts. Then turn of the power and try it again.

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Originally Posted by Joshdta

sounds like you need to blow lightly into the pressure switch. if it or just tap it and see if it shuts. then turn of the power and try it again.

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Which direction do I blow, towards the little black thing( the switch I think) or towards the fan (motor)?

If it did not close then the probem could be at the motor part. Is the vent motor running?? Blow in the tube going to it and see if there may be a obstruction

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Originally Posted by Joshdta

if it did not close then the probem could be at the motor part. is the vent motor running??? blow in the tube going to it and see if there may be a obstruction

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I tried blowing in both directions (with everything turned off). I cannot get air to pass into the motor or into the switch. Yes, the vent motor does come on whenever I try to turn the furnace on.

You will not get air to pass in to the switch but it should go freely into the inducer motor. If not that's your problem.

Well to get the switch to click you would have to suck on the hose not blow in it sense it my work under vacum. Take a small piece of wire and see if you can get it to go into the motor. Do not push hard you do not want the hole to get bigger then it is supaosed to be. Also as you are putting air into or out of the switch listen to see if it is making a small click.

YAY BABY! My gas bill is well on its way to being 3 or 4 hundred buck this month! :D Now I know why there was a paper clip in the furnace. I am not sure if the paper-clip did it when I put it an inch into the vent motor or sucking instead of blowing into the pressure switch did it but hey, that was great.(yes I hear the click) Josh... my kids, wife, and I appreciate you helping me out. We all could have died of frostbite before I would have figured it out on my own. Today, my friend, you are a saint. Have yourself a good night. I am going to crank that baby to 90 and wait until it's hot enough to have a margaritta. And happy halloween too!

Glad you got it going. Good job!!

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Originally Posted by Joshdta

sounds like you need to blow lightly into the pressure switch. if it or just tap it and see if it shuts. then turn of the power and try it again.

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Pressure switches rarily ever go bad. You could have a restriction. A bad bad inducer motor. A clogged condensate line. Worse case , a cracked heat exchanger! Or your exhaust pipe coming of the furnace is not sloped properly and condensation is building up.

Thank you soooooo much for this advice. I returned home tonight to a freezing cold house at 9:30pm so didn't want to pay for emergency hour work. Saw 3 blinking lights and the key that said "combustion air switch" not closing properly. I tried your above advice and it WORKED!! It seemed like some moisture came out of one of the air openings. Anyhow, my family slept well and warm. THANK YOU!! (BTW - I'm a 50 year old woman doing this so any girls reading here, GO FOR IT!! )