I have a 10 year old Amana Air Command 90 Gas Heat system (GCC090X40A) that won't heat. Specifically, when I turn the thermostat to "auto-heat" setting, a blower turns on (combustion blower?), 20 seconds later the igniter begins to glow, a few seconds later it stops. repeat tow more times and then main blower starts blowing air throught the house. The diagnostic light starts blinking when the main blower turns on ( I assume it is in lockout mode at this point). I have tested the rollout switch and it has continuity and trips when exposed to the flame of a match. The pressure switch (2 wires) displays 24 volts on each tap.

I can only think of the computer or gas valve as the culprit. Suggestions?

 

Does the burner flame EVER come on? And when did this start doing this? Have you had the furnace running fine so far this season?

Does this particular furnace have a flame sensor? You can tell, by if you have a singular unexplained thin white? wire that goes to the burner area, separate from the 2 hot surface ignitor wires.

If not, if you only have the two ignitor wires - the ignitor itself functions as a sensor. The resistance in the ignitor has to be just right. You MAY have a weak ignitor that the furnace senses not to open the gas valve due to weak glow from the ignitor. There has to be a certain resistance with these ignitors. I am not sure what that number is. The number 95 comes to mind, but I can't remember for sure. But I could call up my furnace man as we deal with Amana and he is putting those in a lot.

And you HAVE checked your gas meter to make sure that someone from the gas company didn't turn off the gas on you, right? Or, if the gas were shut down due to service repairs somewheres and you have lot's of air now in the line? Keep trying to reset the furnace and let this cycle to continue, say 5 times or more, to rule this out.

Is your furnace a sealed combustion unit? If so,then you wouldn't be able to smell gas flow. BUT - this is what you can do, and I have told others. Reset the furnace. Then, quickly go outside and read the fraction cu. ft. dial on the gas meter to see if it takes a jump. That jump would be that the gas valve is trying to open when the ignitor glows.

Then let us know.

 

The furnace has been working fine for 2 or 3 months. Last week it did the same thing but after one reset it started up and has been fine this week until today. Last week after I reset it, I watched the ignitor glow and the flames ignited. Today, after 5 or 6 resets, there have been no flames at all. I would say the furnace is an "open" combustion unit because I can see the flames burning at each orifice and feel that I would be able to smell gas if it were present. The ignitor has two leads and it glows very bright white when it is trying to light. I also a flame sensor with one lead that is separate from the ignitor.

I have gas supply into my home because my gas hot water heater is working fine.

I do not believe gas is flowing through the furnace because I don't hear anything, I don't smell anything, there is no fire in the combustion area even with an ignition source present, and my gas meter does not appear to be moving. If the meter did move it was not much. I was watching the dial representing 1/2 ft and it showed no appreciable movement as the ignitor went through the start up sequence.

 

When you did the pressure switch reading. is that from tab to ground? or Tab to tab?

If it's tab to tab. then the switch is open... Check you venting.

 

tab to ground

 

Have you followed the wire though other safty switches? (flame roll out, pressure switches?)

If all is ok, then the see if you are getting power to the gas valve.

 

Rollout switch works, pressure switch works. I put a meter between the two leads going to the gas valve and they showed no voltage at any point during the startup sequence.

I assumed that the board was faulty so I jumped the 24v signal from the pressure switch to the gas valve when the ignitor glowed and it fired right up. The only thing left to this layman is that the board is bad.

I found this link from White rodgers, board manufacturer, to be helpful. http://www.white-rodgers.com/pdfs/04...pg_265_270.pdf

Do you think it's dangerous to use the jumper system for a few minutes every couple of hours? I'm thinking at this point that I might be able to order a new board and put it in myself by Wednesday. It looks like a simple matter of unplugging and plugging a few wires. Am I oversimplifying? Any advice would be great.

 

I would really appreciate some help here. To follow up on the last post I made on Sunday, I got a new computer and installed it today. I have the exact same problem! After the heat call, blower runs, ignitor comes on, 10 seconds of hot ignitor, blower goes off. Repeat twice and then lockout.

My solution to keep the house warm has been to jump the 24v signal to the pressure switch right to the hot side of the gas valve. Specifically, I turn the furnace on, wait for the ignitor to glow, then I hook an alligator clip to one side of the roll out switch (which then goes to gas valve) and away it goes. I let it run for 30 minutes then pull the clip and turn off power to the furnace.

Suggestions?