Furnace Lites But Won't Run - HVAC - DIY Chatroom Home Improvement Forum


Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > HVAC

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Display Modes
Old 01-21-2009, 06:19 AM   #1
Home Improvment Contactor
 
Join Date: Jan 2009
Posts: 35
Rewards Points: 25
Default

Furnace lites but won't run


I have a forced air gas furnace.
The thermocouple
glows fine.
The burner lights fine.
The thermocouple goes off. (burner still burning)
Then as soon as the blower starts the burner shut off. It will keep doing this over and over until I manually shut off the unit.
I've wiggled wires and tapped on the metering valve.

Advertisement

Jack of most is offline   Reply With Quote
Old 01-21-2009, 01:49 PM   #2
Member
 
JohnH1's Avatar
 
Join Date: Jan 2009
Location: Chicago, IL.
Posts: 428
Rewards Points: 250
Default

Furnace lites but won't run


What do you mean the thermocouple goes off? Do you mean the pilot goes off IE: no pilot flame. Or are you describing a hot surfice ignitor/ glow bar

Advertisement

JohnH1 is offline   Reply With Quote
Old 01-21-2009, 03:31 PM   #3
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 26,440
Rewards Points: 4,526
Default

Furnace lites but won't run


Wonder if he's calling the HSI the thermocouple.
beenthere is online now   Reply With Quote
Old 01-22-2009, 12:13 AM   #4
Member
 
Join Date: Nov 2008
Location: palm coast fl
Posts: 588
Rewards Points: 500
Default

Furnace lites but won't run


sounds like your cycleing on the limit probably a bad board leave it on fan on till you get it fixed
kennzz05 is offline   Reply With Quote
Old 01-22-2009, 07:02 AM   #5
Home Improvment Contactor
 
Join Date: Jan 2009
Posts: 35
Rewards Points: 25
Default

Furnace lites but won't run


Yes, I was calling the HSI a thermocouple. Does cycling on the limit mean, thermostat is set to a particular temp. which happens to be the temp of the room? What's a bad board? Thanks for all your help!

Last edited by Jack of most; 01-22-2009 at 08:57 AM.
Jack of most is offline   Reply With Quote
Old 01-22-2009, 07:37 PM   #6
Member
 
JohnH1's Avatar
 
Join Date: Jan 2009
Location: Chicago, IL.
Posts: 428
Rewards Points: 250
Default

Furnace lites but won't run


It sounds as if you eather have a bad curcuit board or a bad Heat Exchanger. I have seen a curcuit board act that way. Look at the burner when it begins fireing and watch the burner near the flame senser. When the blower starts do you see the flame pattern change and fluctuate around the senser. If this happens the senser may thing the burner went out and shut the unit down and restart again. This is a sign of a bed heat exchanger.
JohnH1 is offline   Reply With Quote
Old 01-22-2009, 08:29 PM   #7
Newbie
 
Join Date: Jan 2009
Posts: 7
Rewards Points: 10
Default

Furnace lites but won't run


I have a thought of what might be happening. There is a flame sensor that looks like a metal rod about the size of a metal coat hanger. This is going to sense that the burner flame is present. The flame sensor will get a carbon buildup on it and not allow the sensor to detect that the flame ignited. It can run for a few miniutes like your describing and then shut down the burners. The sensoe needs to be removed and cleaned with steel wool or sand clothe. Put it back on and try it. If this is a Ruud or Rheem furnace there should be a amber colored LED on the curcuit board that will light up if the flame sensor is clean.
A/C Williams is offline   Reply With Quote
Old 01-22-2009, 09:52 PM   #8
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 26,440
Rewards Points: 4,526
Default

Furnace lites but won't run


Dirty flame sensor won't let it run long enough to bring the blower on.
What he describes, sounds more like the blower is blowing the flame away from the sensor due to a cracked HX.
beenthere is online now   Reply With Quote
Old 01-24-2009, 11:16 AM   #9
Home Improvment Contactor
 
Join Date: Jan 2009
Posts: 35
Rewards Points: 25
Default

Furnace lites but won't run


The flame pattern didn't change. Thank goodness! You all scared me with the whole cracked HX talk. I'm sure I need a cleaning and service though.
More info: If the thermostat is set at 68 and the inside temp is 68 it does what I explained. If I raise the thermostat to 2 degrees or more above the inside temp it will then run and raise the house temp, but then go into the off and on cycle again. Could this be a bad thermostat? I will also try to clean the flame sensor and report back.

Again, thanks to all.
Jack of most is offline   Reply With Quote
Old 01-24-2009, 12:10 PM   #10
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 26,440
Rewards Points: 4,526
Default

Furnace lites but won't run


Bad stat, or low air flow, and tripping the high limit.
beenthere is online now   Reply With Quote
Old 01-24-2009, 03:36 PM   #11
Member
 
Dr Heat's Avatar
 
Join Date: Jan 2009
Location: Northern Central IL
Posts: 94
Rewards Points: 75
Default

Furnace lites but won't run


check your filter then check dampers to be sure everything is open.
Dr Heat is offline   Reply With Quote
Old 01-24-2009, 03:54 PM   #12
Newbie
 
Join Date: Jan 2009
Posts: 7
Rewards Points: 10
Default

Furnace lites but won't run


You may also want to check if the thermostat has batteries. If they run weak the t-stat can do some strange things sometimes.
A/C Williams is offline   Reply With Quote
Old 01-24-2009, 04:01 PM   #13
Newbie
 
Join Date: Jan 2009
Posts: 7
Rewards Points: 10
Default

Furnace lites but won't run


Also if your control board has LED lights, it may be giving you a code of whats happening. The LED will flash a certain number of times and then have a pause. Look on the back of the blower door and see what to code number says. The blower door will usually have a plastic window to see the LED because if you take the blower door off it will kill the power to the heater and lose the code.
A/C Williams is offline   Reply With Quote
Old 01-25-2009, 12:00 PM   #14
Member
 
JohnH1's Avatar
 
Join Date: Jan 2009
Location: Chicago, IL.
Posts: 428
Rewards Points: 250
Default

Furnace lites but won't run


If you raise the stat and it runs long enough to reach the set temp and then starts short cycling again your heat anticapator or cycle rate on the t-stat may be set slightly to short. What type of thermostat do you have?
JohnH1 is offline   Reply With Quote
Old 01-25-2009, 01:14 PM   #15
Home Improvment Contactor
 
Join Date: Jan 2009
Posts: 35
Rewards Points: 25
Default

Furnace lites but won't run


Lux 500 programmable
I cleaned the flame sensor and replaced the batteries in the stat.(Didn't know they were there) No LEDs. I change the filter every 3 months or less.
I think it's working! If it was just the batteries, I feel like an idiot with 25+ years of home repair experience. Always shied away or referred out HVAC situations. THANK YOU, THANK YOU, THANK YOU! I learned a lot and I feel like I owe you all something but all I can do is leave you with this... I hope I made you smile cause I am.

Advertisement


Last edited by Jack of most; 01-25-2009 at 01:16 PM.
Jack of most is offline   Reply With Quote
Reply


Thread Tools
Display Modes

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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Lennox Furnace G27M Series Unreliable operation: pressure switch or else? sheppard1977 HVAC 7 01-14-2013 06:42 PM
Furnace air filtration advice stephen_smith HVAC 7 12-24-2010 03:24 AM
Oil furnace does not fire up sbhavinm HVAC 5 01-17-2009 08:06 AM
Problems with new furnace..Overheating, having to reset. Furnace too big? Tommy2 HVAC 41 12-01-2008 02:55 PM
New Cased Coil - Install to Furnace - PICTURES!! hartkem HVAC 39 11-18-2008 02:45 AM




Top of Page | View New Posts