Need help w/furnace that won't fire

Michael D · 11-26-2012, 02:31 AM

Hello,

A problem that "self-corrected" for a month just came back in a new form. When the thermostat in in the AUTO position, raising the desired temp produces a click, but no response from the unit. When I flip it to ON, the fan blower starts, but the inducer doesn't thus the unit doesn't fire. Below is a description of the problem we had a month ago in case any of that info sheds light the current one:

"I've got an eight-year-old electric ignition Aire-Flo furnace with a Honeywell valve. When the thermostat or power is reset, the unit will fire up normally--blower then burner--but the flame goes out after 1-3 minutes. It will attempt several short and long phases of restart, sometimes getting as far as the ignitor glowing (though not always). When it does get as far as the ignitor glowing, about half the time it clicks and lights. However, these subsequent ignitions always go out after 10-45 seconds. So it's only successfully lighting every 3-5 minutes and only staying lit for a couple minutes max.

I've already pulled and sanded the flame sensor (really didn't look dirty). since it sometimes burns for 2-3 minutes, if it's a sensor issue, it's not consistent. Same with the ignitor--though the cycle doesn't always get to the ignition stage, or does and shuts down before the gas is released, the ignitor should not be a factor in the flame going out once it's lit. Problem also occurs with the panel open, so I don't suspect any airflow issues. I'm pretty new to this, but the only other thing I can think of is some timing issue with the valve itself. Hopefully someone here can suggest otherwise."

I finally got someone to take a look at it, but the problem "disappeared" and the system ran just fine. We checked the pressure switch, flame sensor, etc, with a voltmeter--all were good. The light on the gas valve would not produce an error code. We've had heat for a month...and now this.

Any suggestions would be greatly appreciated.

NiNe O · 11-26-2012, 06:07 AM

I would start with pressure switch, clean out the tubing, carefully check the switch itself, it may have debris, check the points where the pressure tubing connects to the furnace, I use a small service driver to make sure those ports are clear.

Michael D · 11-26-2012, 06:56 AM

Yep, tubing is all clear--would a bad/clogged pressure switch keep the inducer from even trying to start or just shut it down when it did? (The problem I had a month ago involved some short, "false" starts...)

NiNe O · 11-26-2012, 07:43 AM

The furnace will start the inducer first on a call for heat. Provided the safety circuit(s) are fine.

coolin4u · 11-26-2012, 07:51 AM

check for blockages on the intake pipe if vented outside,i have seen this scenario several times when leaves,mice other debris end up in the pipe.

Doc Holliday · 11-26-2012, 08:27 AM

Honeywell Smart Valve?

bclark24 · 11-26-2012, 11:25 AM

I would try jumping out the pressure switch ive had the same problem before and its usually the pressure switch if not I would go thru all the sensors. Also see if the board is giving you an error code you can read

11-26-2012, 02:31 AM	#1
Michael D Newbie Join Date: Oct 2012 Posts: 15	Need help w/furnace that won't fire Hello, A problem that "self-corrected" for a month just came back in a new form. When the thermostat in in the AUTO position, raising the desired temp produces a click, but no response from the unit. When I flip it to ON, the fan blower starts, but the inducer doesn't thus the unit doesn't fire. Below is a description of the problem we had a month ago in case any of that info sheds light the current one: "I've got an eight-year-old electric ignition Aire-Flo furnace with a Honeywell valve. When the thermostat or power is reset, the unit will fire up normally--blower then burner--but the flame goes out after 1-3 minutes. It will attempt several short and long phases of restart, sometimes getting as far as the ignitor glowing (though not always). When it does get as far as the ignitor glowing, about half the time it clicks and lights. However, these subsequent ignitions always go out after 10-45 seconds. So it's only successfully lighting every 3-5 minutes and only staying lit for a couple minutes max. I've already pulled and sanded the flame sensor (really didn't look dirty). since it sometimes burns for 2-3 minutes, if it's a sensor issue, it's not consistent. Same with the ignitor--though the cycle doesn't always get to the ignition stage, or does and shuts down before the gas is released, the ignitor should not be a factor in the flame going out once it's lit. Problem also occurs with the panel open, so I don't suspect any airflow issues. I'm pretty new to this, but the only other thing I can think of is some timing issue with the valve itself. Hopefully someone here can suggest otherwise." I finally got someone to take a look at it, but the problem "disappeared" and the system ran just fine. We checked the pressure switch, flame sensor, etc, with a voltmeter--all were good. The light on the gas valve would not produce an error code. We've had heat for a month...and now this. Any suggestions would be greatly appreciated.

11-26-2012, 06:07 AM	#2
NiNe O Items wanted: Time Join Date: Nov 2012 Location: Howell, MI Posts: 195	Need help w/furnace that won't fire I would start with pressure switch, clean out the tubing, carefully check the switch itself, it may have debris, check the points where the pressure tubing connects to the furnace, I use a small service driver to make sure those ports are clear.

11-26-2012, 06:56 AM	#3
Michael D Newbie Join Date: Oct 2012 Posts: 15	Need help w/furnace that won't fire Yep, tubing is all clear--would a bad/clogged pressure switch keep the inducer from even trying to start or just shut it down when it did? (The problem I had a month ago involved some short, "false" starts...)

11-26-2012, 07:43 AM	#4
NiNe O Items wanted: Time Join Date: Nov 2012 Location: Howell, MI Posts: 195	Need help w/furnace that won't fire The furnace will start the inducer first on a call for heat. Provided the safety circuit(s) are fine.

11-26-2012, 07:51 AM	#5
coolin4u Newbie Join Date: Nov 2012 Posts: 1	Need help w/furnace that won't fire check for blockages on the intake pipe if vented outside,i have seen this scenario several times when leaves,mice other debris end up in the pipe.

Need help w/furnace that won't fire