Furnaces... Damn them! | GTAMotorcycle.com

Furnaces... Damn them!

gqelements

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Furnace is acting up...

Everything works, but the basement furnace won't blow hot air/activate when thermostat is in 'auto' mode... ie, even though the temp on the thermostat is clearly below the 'HOLD" or "Schedule" setting (even by 10 degrees, I tried going extreme) hot air won't kick in. I can force it by setting fan setting on the thermostat to 'ON' and it does blow hot air, but it just won't start up on its own if left at "AUTO"... I tried switching thermostats in case it was a temp sensor. Basement t-stat works great upstairs but the upstairs unit (that was working fine there) fails to kick the basement furnace/blower, so the problem must be more than just the on-wall t-stat...

Any ideas what it could be?
 
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Explain your setup more. You have a separate basement furnace that only lights the burner if you manually force the fan on? Or is this a single furnace with two thermostats and a damper or transfer fan arrangement?
 
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Explain your setup more. You have a separate basement furnace that only lights the burner if you manually force the fan on? Or is this a single furnace with two thermostats and a damper or transfer fan arrangement?

2 furnaces with 2 thermostats, one controls/heats the first 2 floors and the other set for upstairs floors....

Our furnace has a trouble light system that pops up a code. Does yours?

No light :(
 
2 furnaces with 2 thermostats, one controls/heats the first 2 floors and the other set for upstairs floors....

Thanks. Normally the thermostat isn't that complicated, it calls for heat and the furnace knows that means to ramp up the fan and light the burner. I would lean towards control board.

It is interesting that manually forcing the fan on causes it to light. Does it stay burning after the temp passes the set point? It sounds like the control board isn't starting the fan and then using it's logic not to light. If the fan is already running, the rest of the board is happy (assuming it stops firing at thermostat setpoint).
 
Usually the relays on the control board give out first, at least in my case. Take a pic of the control board and post it, should be easy enough to find a replacement after that.
 
Furnace is acting up...

I can force it by setting fan setting on the thermostat to 'ON' and it does blow hot air, but it just won't start up on its own if left at "AUTO"... I tried switching thermostats in case it was a temp sensor.

This doesn't sound right. Turning FAN on should only turn on the blower, with no heat. Only way to get heat with FAN switch is if you accidentally connected the heat terminal "W" wire to the fan terminal "G". If this is the case, then all you have to do is sort out your wiring connections.

What happens in AUTO?
Nothing at all, silence from the furnace? Probably bad control board since you already checked the thermostat.

Or do you hear a bunch of noises from the furnace but it doesn't stay on and give you heat? Probably bad sensors, there's 3~4 diff sensors that could stop the furnace from staying lit.
 
Your problem sounds similar to one I had earlier this winter. Have you tried cleaning the flame sensor?

[video=youtube;R7AKPgBB_R4]https://www.youtube.com/watch?v=R7AKPgBB_R4[/video]
 
Your problem sounds similar to one I had earlier this winter. Have you tried cleaning the flame sensor?

[video=youtube;R7AKPgBB_R4]https://www.youtube.com/watch?v=R7AKPgBB_R4[/video]

I was just about to post this . Fixed my furnace problem .
 
Thank you all for very informative feedback. Problem solved by installing The Nest thermostat :)

I'm sure this approach may not be addressing the root cause. But it seems that for now, all is well....
 
Disconnect the "I'm about to leave for an important date" sensor that causes the furnace to shut down at the most inopportune time.
 

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