Puddin' Man wrote:
On Thu, 20 Nov 2008 20:18:17 -0700, Tony Hwang wrote:

Puddin' Man wrote:
Little bungalow in US midwest. Heil gas furnace on it's 3rd season.
Standard forced air, std install. Gen'lly works well.

heat cycle:
1.) tstat calls for heat
2.) inducer fan spins
3.) igniter element (like glow plug) heats up
4.) after about 20 sec. for 1.) and 2.), gas valve opens, burners fire
5.) safety: if heat sensor stays cold, gas valve closes.

Works OK about 2 of 3 times.

The third time, works OK thru 3.), I get a click like when the
gas valve opens, but the burners don't fire. Then it goes
back thru the cycle and works.

The igniter always heats, I can see it glowing.

Igniter's not getting hot enough? Other ideas??

Thx,
P

"Take Yo' Hand Out My Pocket (I Ain't Got Nothing What Belongs To You)!"
- Rice Miller, who probably never even _heard_ of GW Bush, Paulson, etc
Hi,
Common problem. Clean the flame sensor with emery cloth.

If you're talking about the heat sensor in 5.), I don't understand.

When flame comes on sensor generates very small amount of current
which is sensed by control board logic.

The inducer runs it's little cycle, the igniter glows. It *sounds*
like the gas valve opens, but the burners don't fire.

You're saying maybe the heat sensor has crud from previous cycles
and shuts the gas valve down before the burners have a chance to
fire???

The burners don't fire and then shut down prematurely. They
fail to fire at all.

P

"Take Yo' Hand Out My Pocket (I Ain't Got Nothing What Belongs To You)!"
- Rice Miller, who probably never even _heard_ of GW Bush, Paulson, etc
Hi,
When inducer motor comes upto speed pressure switch should trigger next
is ignitor coming on(if it's not spark type, it should glow bright) then
valve opens, gas ignites, flame sensed, blower comes on. What model
furnace? No trouble code?