# Lennox 80UHG doesnt blow heat



## Marty S. (Oct 31, 2009)

Look at the diagnostic lights and compare the flashes to the label on the door. Probably locked out in watchguard mode. Shut the power off, clean the flame sensor and try starting again.


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## stiksandstones (Jan 30, 2011)

Marty S. said:


> Look at the diagnostic lights and compare the flashes to the label on the door. Probably locked out in watchguard mode. Shut the power off, clean the flame sensor and try starting again.


56° this morning in here! yikes, in so cal! (lovely weather proofing on this house I see).
Just crawled up in attic, I see 2 green LED's flashing, together, don't remember seeing a diagnostic panel, but will check again.


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## hvactech126 (Nov 11, 2010)

should be on the blower door, may be on inside of the door. were they flashing alternately or simultaneous? flashing fast or slow? Did you turn power off and back on? this will reset the control and may get you temporary heat. We do need the diagnostic code to help figure out the cause to come up with a repair though. It would also help if after you reset the control if you stay and watch a ignition sequence and post here what happens.... I would start with cleaning the flame sensor though.







or


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## stiksandstones (Jan 30, 2011)

Found the sensor, pulled out and used steel wool to clean it. Corrosion was not too bad though?
Anyways, put it back in, still same thing: the thermostat clicks some sort of action happens at the furnace, but the big blower NOR flame come on.

The lights flash together with about 1-1.5 second gaps between I'd say?

Heater did not work 2 years ago, guy charged me $800 for a new circuit board or something? I don't have $800 right now, let alone $8, so I was hoping for an easy fix :laughing:


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## stiksandstones (Jan 30, 2011)

i take that back on the LEDs, they are rapidly flashing, together when its trying to start. I don't know the proper startup phase so forgive my terminology. There is a humming coming from the furnace, but nothing is 'firing' nor is the big main fan blowing. I can get the fan/blower? to go if I put the thermostat to ON vs AUTO, but no heat is happening. Maybe try cleaning the sensor again? doubtful I guess.


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## hvactech126 (Nov 11, 2010)

did you find the diagnostic legend?
that sounds like a stat problem, check for batteries, if your stat has them, then replace them.

otherwise remove wires from R and W and twist together, this should change the flash at the furnace.

MANUAL see page 8 for diagnostic information


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## stiksandstones (Jan 30, 2011)

hvactech126 said:


> did you find the diagnostic legend?
> that sounds like a stat problem, check for batteries, if your stat has them, then replace them.
> 
> otherwise remove wires from R and W and twist together, this should change the flash at the furnace.
> ...


diagnostic legend, that is what you linked to at the bottom, right?
and 'stat' you mean thermostat on the wall right?
remove wires from where?


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## hvactech126 (Nov 11, 2010)

this is probably the problem, see if the humming is coming from here. if it is, the motor is stuck. if this is not running during call for heat then check for 120V ,with a multimeter, to the motor.


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## Marty S. (Oct 31, 2009)

Both lights fast flashing means the thermostat is calling for heat. The inducer motor should come on next. Does it?


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## stiksandstones (Jan 30, 2011)

Your image did not show.

And the diagnostic tells me everything is fine (green lights) clearly everything is not fine.


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## stiksandstones (Jan 30, 2011)

Marty S. said:


> Both lights fast flashing means the thermostat is calling for heat. The inducer motor should come on next. Does it?


Like I said in the original post, I know nothing about furnaces, so I don't know what an inducer motor is. But also as I said, the thermostat 'clicks' and the furnace starts something, perhaps the inducer motor? all I know is I don't hear the usual BURNER sound NOR the big fan/blower that spits out hot air around the house. Something is turning on in furnace, just no fire or blower (blower I think is name eh? of the big fan that blows the actual hot air).


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## yuri (Nov 29, 2008)

Is the ventor fan that pushes the smoke to the chimney running. If so carefully remove the tube from the pressure switch hose where it attaches to the collector box/furnace (NOT the switch itself) and poke a paper clip/small bit thru that hole. It should be giving you a open pressure switch code but you are having a hard time reading it. Look at the pic in here
http://www.hvacparts.ca/LennoxPDF/80UHG.pdf
the inducer is the fan at the top and the pressure switch is below it.


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## Marty S. (Oct 31, 2009)

The inducer is a little motor where the flue hooks up. It comes on and closes a pressure switch if the flue is clear. Check the flue for a dead bird.

If the pressure switch doesn't close then the furnace will not continue the start up sequence.


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## hvactech126 (Nov 11, 2010)

inducer.... again go to manual see page 8 for diagnostic code and below that is the sequence of operation. Page 25 starts diagnostics


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## stiksandstones (Jan 30, 2011)

Ok, just to confirm the lights. The led's flash green together, when thermostat is off, they flash slowly. When I turn on thermostat to get heat, the green lights flash quickly. So this says everything is A-OK. 

But, after that inducer is blowing (I think thats what I hear spinning/activated) is shuts off after a couple minutes, then its just ONE led flashing green.


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## hvactech126 (Nov 11, 2010)

did you check that MANUAL!!!!!!!!!!!!!!!! WHICH LED IS IT DIAG 1 OR 2? SEE MANUAL!!!!!!!!!!


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## stiksandstones (Jan 30, 2011)

STOP YELLING!!! :laughing:

if I am reading the codes correctly (led on the left (#1 ?)slow flash and led on right (#2 ?) OFF)
That is 
"flame sensed without gas valve energized"

what now?


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## stiksandstones (Jan 30, 2011)

stiksandstones said:


> STOP YELLING!!! :laughing:
> 
> if I am reading the codes correctly (led on the left (#1 ?)slow flash and led on right (#2 ?) OFF)
> That is
> ...


Going to take panel off now and make sure those LED codes are correct in regard to which one is Led#1 and #2, because the error I am getting is extremely rare according to google...so perhaps I am reading the board upside down? In that case the code would be:
"pressure switch open or has opened 5 times during a single call for heat:
OR blocked inlet/exaust ventOR condensate line blockedORpressure switch closed prior to activation of combustion air blower.


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## stiksandstones (Jan 30, 2011)

ok, DS2 was slow flash, DS1 was OFF. so it is:

"pressure switch open or has opened 5 times during a single call for heat:
OR blocked inlet/exaust vent 
OR condensate line blocked
ORpressure switch closed prior to activation of combustion air blower"


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## stiksandstones (Jan 30, 2011)

so that inducer motor seems to have a metal pipe exaust deal leading to the roof, I removed screws at the inducer vent pipe, looked inside for some immediate blockage, but IF something is blocking it, must be on the outside (dead bird as someone mentioned?) but this exaust pipe has some tricky joints/seams, dont know how to unattach them.

help


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## hvactech126 (Nov 11, 2010)

OK. is the draft motor inducer operating? if so, then there is a ,typically orange, hose connected to the assembly. Remove the hose and using a small drill bit or paper clip ream out the port where the hose was, do this with the power off.

if the motor does not run, check for 120V to inducer with furnace on and calling for heat


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## stiksandstones (Jan 30, 2011)

hvactech126 said:


> OK. is the draft motor inducer operating? if so, then there is a ,typically orange, hose connected to the assembly. Remove the hose and using a small drill bit or paper clip ream out the port where the hose was, do this with the power off.
> 
> if the motor does not run, check for 120V to inducer with furnace on and calling for heat


The inducer motor pic you showed me...the BLACK WHEEL that spins, that is spinning, if that is what you are talking about.


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## yuri (Nov 29, 2008)

OY, it's like pulling teeth. 3 high priced Pro's trying to help. It doesn't get any better than that.:laughing:


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## yuri (Nov 29, 2008)

Yes, just follow our instructions verbatim and we will get you thru this. Try unplug the hole from the pressure switch tube at the part where it attaches to the furnace. Also remove the hose from the switch and blow thru it w/o being attached to the switch. DO NOT suck or blow into the switch irregardless of what you read on the net.


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## hvactech126 (Nov 11, 2010)

if the black wheel is spinning on the back of the motor on its own, with out you spinning it, then yes it is running. Do as I said with the paperclip/drillbit.


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## hvactech126 (Nov 11, 2010)

very good point YURI, I hate reading that, it can ruin the diaphragm in the p/s


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## stiksandstones (Jan 30, 2011)

Reamed a tiny bit with a like-sized bit into that hole as you said, just used fingers to spin bit around to 'open' it up a bit, it looked a bit corroded/rusty even perhaps.

I HAVE HEAT!

Thanks so much you guys!

First, getting shower remodeling help in here and now this!

STOKED!
thanks!


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## hvactech126 (Nov 11, 2010)

no problem, its what we do! Glad we could help!


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## yuri (Nov 29, 2008)

At 3X $100/hr for 3 Pro's you got a great deal. Pay it forward and help someone else with what you are good at.:thumbsup:


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## BigTee (Jan 3, 2012)

OMG. You guys are life savers.
My heater stopped working with EXACT same symptoms. The temp is supposed to get down to near freezing tonight and my heater wasn't working.

I read this thread 3 times and studied the manual before going up in the attic to investigate my Lenox 80UHG unit.
After unplugging the hole of the inducer, I now have heat and my family can sleep without being cold.

THANK YOU for this thread.

YOU ROCK!


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