# Furnace Troubleshoot



## Cache (Sep 18, 2007)

Hey guys,

I have a Concord 90 plus efficiency furnace with the following symptoms that is unable to keep the house warm and we are hitting 15 below zero at night these days.

1) thermostat calls for heat
2) Inducer motor turns on
3) 5 second pause with inducer running
4) Igniter starts to glow
5) Gas fires
6) 5 second pause
7) fan blower runs for about 5 minutes 
8) furnace shuts off before reaching target temp.

after about 5 minutes

9) inducer motor starts
10) 5 sec pause
11) igniter glows
12) gas fires 
13) furnace shuts off

after about 5 minutes

14) inducer starts 
15) shuts off after about 3 seconds

If I shut the heat off for about 15-30 minutes I can turn it back on and it will start right up for one cycle of 5-10 minutes, then shuts off and nothing. If I leave the temp stat on all day the inducer motor is hot to the touch but furnace doesn't heat the house.

Any suggestions? My first thought was that maybe the inducer motor is overheating. A local HVAC suggested that those motors shouldn't get hot.


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## Cache (Sep 18, 2007)

Forgot to mention, the unit is 3 years old.

Also, if I turn the temp stat fan setting to "on" instead of "auto" nothing happens. But I can hear a constant hum coming from the fan motor. Diagnostic code flashes 3 times meaning pressure switch is open. I don't see how that would explain main fan not starting when temp stat switched to "on". hmmmmm???


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## beenthere (Mar 5, 2009)

Check amp draw of inducer. Also check air filter. Clean drain lines.


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## Cache (Sep 18, 2007)

beenthere said:


> Check amp draw of inducer. Also check air filter. Clean drain lines.



Thanks for the suggestions. Already replaced filter. Going to check drain lines today.


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## Cache (Sep 18, 2007)

Alright, I nailed down the issue and implemented a temporary fix. 

After Beenthere mentioned drain lines I noticed that whenever it would almost fire up there was a gargling sound like a line was filled with water. There is a condensate line running from the flexible exhaust collar on the inducer to the cold end header box. I pulled the end of the hose off the exhaust collar and blew into it and a bunch of water went down the drain line. After doing this, the furnace would start right up and run for 5-10 minutes before shutting off again. 

I'm assuming there is a pump in the bottom of that header box that is meant to pump the condensate to the drain. For some reason that isn't working. Not sure if I need a new part or not. 

In the mean time, I ran two hoses direct to the floor drain. One from the exhaust collar, and the other from where the condensate line attached to the header box. With this fix, the furnace runs without problems; better than it ever has in fact. I was surprised by how much water comes out of the bottom of the header box. Probably just because we are in a high humidity inversion right now. 

Eventually I'll try to figure out why the header box isn't expelling the water. Any suggestions would be helpful.


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## beenthere (Mar 5, 2009)

Those hoses should run to a trap. its probably dirty and needs cleaned out.


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## Cache (Sep 18, 2007)

beenthere said:


> Those hoses should run to a trap. its probably dirty and needs cleaned out.


Is this the trap you refer to? Circled in red. Usually there is a trap in the PVC drain line, but this furnace doesn't have that. Instead this reservoir at the bottom of the header box seems to pump the water into the drain line which runs to a floor drain.


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## beenthere (Mar 5, 2009)

yes, and it may be dirty and slowing the water from draining properly.


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