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-   -   Lennox Furnace 80UHG3 Won't Ignite (http://www.diychatroom.com/f17/lennox-furnace-80uhg3-wont-ignite-65162/)

KeithGP 02-23-2010 12:44 PM

Lennox Furnace 80UHG3 Won't Ignite
 
Help,

I'm stuck and I'm sure I've done something wrong. My igniter won't light so I bought a universal silicon nitride igniter and cut the wires from my old Lennox 41K5601 and put the wiring on a GoodParts 700-4-1 igniter. No change.

1) Do I need to get a Lennox Igniter?

2) The Diag code that I am receiving is DIAG NO. 1 OFF and DIAG NO. 2 SLOW FLASH which states PRESSURE SWITCH OPEN OR HAS OPENED 5 TIMES DURING A SINGLE CALL FOR HEAT, OR: BLOCKED INLET/EXHAUST VENT, OR: CONDENSATE LINE BLOCKED, OR: PRESSURE SWITCH CLOSED PRIOR TO ACTIVATION OF COMBUSTION AIR BLOWER

Maybe my igniter wasn't bad after all. How do I check the things it asked for on the Diagnostic codes?

Lennox Model 80UHG3
http://www.keith71.com/panel.jpg
I have done these things:

1) Tried sucking in the red inlet valve to make the valve close (if that makes sense)
http://www.keith71.com/patchjob.jpg
2) Used a voltmeter to verify that I am getting 120V (actually 118.6V) across the igniter but it;s not igniting.
http://www.keith71.com/oldigniter.jpg

http://www.keith71.com/mainboard.jpg

http://www.keith71.com/diagcodes.jpg

Marty S. 02-23-2010 09:19 PM

You can use the universal ignitor. If the new one has 118 volts as posted and isn't red hot then it's bad.

KeithGP 02-23-2010 09:41 PM

I got the bright idea to try the igniter from the other furnace upstairs. It did not work either. I believe the problem is the pressure switch. I don't think it is properly telling the board to engage the igniter so it's not even starting. The diagnostic code mentions the switch maybe open or closed so it could be bad. I'm gonna replace it tomorrow for $58 and try. Worse case I have new parts.

Marty S. 02-24-2010 06:19 AM

Check the pressure switch ,vacuum line, inducer port and flue before replacing the part. Odds are pressure switch is not broken but doing its job.

KeithGP 02-24-2010 06:51 PM

Marty,

IT FIXED! ALL GLORY TO GOD! Here is how I fixed it. I have this $58 part that I don't need but the experience is worth it. I'm gonna try to eBay the part because the older gentleman I bought it from is the guy that gave me the last tidbit of information that got this thing going. My papa-in-law, an ex-HVAC guy from awhile back put me onto the igniter which wasn't the problem but at least got me to read the DIAG codes. Thanks Pa Pa! The DIAG codes got me here into this forum to ask about the pressure switch. It also helped me download a parts and service manual for free online so I would at least know what terminology to be using. I got all bright and macho and replaced the pressure switch since I tried sucking the pressure switch so that it would close and the igniter would light. No go. Reading further tells me that it's not that simple. The switch is supposed to close, then open for a bit to confirm operation.

I wish I had read your post before buying the new switch, but it was worth it because I met a nice older gentleman at Bon Air in Grand Prairie, TX named Cal who gave me the last tidbit of info. He said to take the vent off and the hose and see if debris is inside. I saw a little debris which made me wonder if the little nozzle where the hose connects was blocked. It was. I tried blowing through the hose to dislodge it but that didn't work. I ended up putting a wire clothes hanger through it to unblock it.

Walla! I got heat!

Thank you Marty for your part in bringing my furnace back to life.

hvaclover 09-24-2010 08:04 PM

Allah sucks

JohnJames 10-31-2011 11:37 PM

Quote:

Originally Posted by hvaclover (Post 506791)
Allah sucks

It is people like you who give Americans a bad image.

if you don't have something nice to say, don't say it.

//

congratz on your furnace issue, I have a similar one. My furnace does not ignite, I can see the spark, I can smell the gas and hear the flow of gas as well. but it does not ignite. What can the issue be?

how 11-01-2011 12:28 AM

What furnace do you have? Is it a direct Spark to the main burners or a pilot?

savich13 03-22-2014 11:22 AM

old post but it helped - fixed
 
My lennox furnace would glow (ignitor) & briefly ignite but would shutdown after a few seconds. read this post and released better get the service manual to determine the LED blinky codes. dual LEDs were alternating slowly. Read service manual and it stated check flame sensor. It stated clean with steel pad or replace. I noticed mine was white insteat of grey/silver. I cleaned it with steel pad & replaced. Restarted furnace and its now working.:thumbsup:


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