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lacey8434 · Oct 26, 2013, 02:18 PM

I have a concord 80 plus furnace. I tried turning it on and it runs for a few seconds and shuts off. Sometimes it will ignite and sometimes it won't. I replaced the flame sensor and the pressure switch, I have sucked/blown on the tube and cleaned what the tube connects to with a small piece of wire but no luck. I also go on the roof and checked the flue or whatever the pipe is up there and it is not clogged that I can see. The LED light on the circuit board is flashing three times which should mean the pressure switch is open with the inducer on.

Grady White · Oct 27, 2013, 09:03 AM

You will need a volt meter to confirm the switch is actually open. Do you have one & know how to use it?

Teknik · Nov 10, 2013, 11:38 AM

Originally Posted by Grady White

You will need a volt meter to confirm the switch is actually open. Do you have one & know how to use it?

I am having the same problem and stumbled across this page. I have a volt meter and know how to use it, I just don't know how to check the switch.

Grady White · Nov 10, 2013, 02:46 PM

Teknik:
Set the meter for AC volts. Have the furnace calling for heat & the venter running. Measure voltage across the switch. If you get +/- 24 volts, the switch is indeed open. No voltage indicates a closed switch.

Exactly what is the furnace doing? Try to be as detailed as possible.

Teknik · Nov 10, 2013, 08:13 PM

Hey thanks for the reply. I'm not freezing or anything because the furnace is running right now.

It's weird. It will work for a month, then stop. I'll go restart it and it will do 1 of 3 things.
1. Fan comes on, no flames appear in the box, shuts off and gives the inducer on error
2. Fan comes on, Flames shoot for about a second, shuts off and gives the same message.
3. Furnace starts normally, runs 10 minutes, then shuts off.

I know it's not the air intake. That was easy to check.
I know it's not the exhaust. I popped the pipe off and just let it try to run it a couple times with no luck.
I've sucked on more hoses than I can count.
I took out the thermostat out of the box and cleaned it.
None of the water hoses are clogged
I ran the water pump a couple times by pouring water into it.

I'm not sure what else it could be. It may just be that switch and sometimes it works, sometimes it doesn't.

Grady White · Nov 11, 2013, 08:22 PM

Grrrr. I hate intermittent problems. I'm crazy enough without having to deal with a furnace which will work just fine while I'm there but such is the life of a service guy.

It is possible there is some junk intermittently blocking the port(s) to which the pressre switch connects. I've often used a small drill bit to clean them. If it's a piece of rust or something like that, sometimes you'll just push it out of the way for the time being.

Teknik · Nov 12, 2013, 10:43 AM

Originally Posted by Grady White

Grrrr. I hate intermittent problems. I'm crazy enough without having to deal with a furnace which will work just fine while I'm there but such is the life of a service guy.

It is possible there is some junk intermittently blocking the port(s) to which the pressre switch connects. I've often used a small drill bit to clean them. If it's a piece of rust or something like that, sometimes you'll just push it out of the way for the time being.

I may just replace the switch if I can figure it out, and I can't imagine it's that hard. The furnace is a Duquesne ,an it's only 3 years old. We've been having this problem since it's second year as far as I can remember.

Grady White · Nov 12, 2013, 07:44 PM

99+% probablility the pressure switch is not the problem.

Teknik · Mar 26, 2014, 02:51 PM

For anyone that comes across this post looking for an answer like I did...

Shortly after my post on Nov 12, 2013 I got the same problem again. I went down and firmly tapped on the pressure switch with a nut driver (just needed something blunt to hit it with) and it's worked fine since. I'd imagine it's a temp fix to a permanent problem, but I think I know it is the switch now.