Lennox G40UH(X) Series Furnace

Reply

  #1  
Old 12-12-10, 03:27 PM
dlamon's Avatar
Member
Thread Starter
Join Date: Dec 2010
Location: USA
Posts: 2
Received 0 Votes on 0 Posts
Exclamation Lennox G40UH(X) Series Furnace

My furnace won't heat continually. The fan turns on, and the burners will turn on for only a couple seconds, then shut off. This will happen 4 times, and then stop completely. The indicator lights are "alternating slow" flashing. The manual says it's in "watchguard", but the manual gives no help on how to fix it. Is this a doityourself fix, or do I need to call someone?

FYI--Temps are in the single digits or below zero this weekend end and it's getting pretty cold, any help would be greatly appreciated.
 
Sponsored Links
  #2  
Old 12-12-10, 04:15 PM
SeattlePioneer's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Jul 2007
Location: Seattle, Wa
Posts: 5,503
Received 0 Votes on 0 Posts
The flame sensor tends to get covered with invisible oxides so the control module can't verify that the main burners are lit, so it shuts off the main burner gas and tries again.


The flame sensor is on the opposite side of the furnace from the hot surface ignitor. It's a small rod that sticks up into the burner flame with a wire going back to the control module.

Remove the flame sensor and clean it with a wire brush. Reinstall it and try again.

Cleaning the flame sensor annually is part of furnace maintenance.
 
  #3  
Old 12-12-10, 07:58 PM
dlamon's Avatar
Member
Thread Starter
Join Date: Dec 2010
Location: USA
Posts: 2
Received 0 Votes on 0 Posts
Thank you, thank you, THANK YOU! An easy fix, and everything is working great.
 
  #4  
Old 12-14-10, 08:56 PM
Member
Join Date: Dec 2010
Location: usa
Posts: 1
Received 0 Votes on 0 Posts
I am also having same issues, would you be able to help me locate the flame sensor? Funny thing about this is that some times it works fine for a few days, and sometimes it needs to be turned off and back on.
 
  #5  
Old 12-14-10, 10:17 PM
SeattlePioneer's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Jul 2007
Location: Seattle, Wa
Posts: 5,503
Received 0 Votes on 0 Posts
It rapidly becomes confusing when people piggyback one problem on top of another --- and VERY OFTEN, what people think are the same problems are not.

So my suggestion is to start a new thread and re post the problem you are having with your furnace.
 
  #6  
Old 12-27-10, 08:06 AM
Member
Join Date: Dec 2010
Location: USA
Posts: 2
Received 0 Votes on 0 Posts
Thank You so much with this great information. My problem was the same as others. I just got on here and the answer solved mine. Thank You again. By the way I have G50DF-36-070-03
 
  #7  
Old 01-11-11, 06:59 PM
Member
Join Date: Jan 2011
Location: USA
Posts: 1
Received 0 Votes on 0 Posts
Thank you SeattlePioneer! This worked like a charm for me too!
 
  #8  
Old 03-03-13, 12:44 PM
Member
Join Date: Mar 2013
Location: USA
Posts: 1
Received 0 Votes on 0 Posts
Dude!

THAAAAAANK YOOOOOOOU! 5 kids + 3AM + 6 degrees + no heat + no money = Bad.
+ your help... dad is now a hero and my family are not ice cubes!
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes
 
Ask a Question
Question Title:
Description:
Your question will be posted in: