# Amana Air Command 90 furnace not igniting



## rich_kildow (Feb 7, 2012)

I have an Amana Air Command 90 updraft furnace that has been failing to ignite lately. This started as intermittently not recovering when the thermostat sent a call for heat, but eventually it would, especially if you cycled it from Off to heat a few times. Now I can't get it to ignite at all.

I've jumpered the R to W wires in the thermostat and it starts the ignition sequence by firing up the draft induction motor but I don't get any flame. The ignitor does glow hot but the flame never starts. I found the service manual and will start troubleshooting a couple things when I get home from work, but does this ring a bell for anybody? 

The red LED light on the board is blinking twice, which according to the manual indicates a problem with the pressure switch. I was under the impression that the ignitor wouldn't glow if the pressure switch didn't engage, but jumping that is the first thing I'm going to check. I also read somewhere to make sure that gasket behind the draft induction motor was intact and the motor mounted securely as if it is not, air will leak in and it won't establish the pressure needed to trip the switch and open gas valve.


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## yuri (Nov 29, 2008)

You are right. the pressure switch is a critical safety device and must prove before the ignition sequence begins. you may have a faulty board. Amana and Goodman put the limit control in sequence with the gas valve but other than that they are the same as any other brand. sounds like a bad board to me. Post the model and serial # and some pics of it with both doors off. I don't see that furnace a lot and it is possible they enagage the igniter but not the gas valve so that is still safe but hard on the igniter. G and A brand kinda do a few things different. Where the tubing from the pressure switch attaches to the collector box remove it and poke a paper clip and then drill bit in there as it plugs with crap sometimes. Check your venting for obstructions. *DO NOT* bypass a pressure switch because if there is not enough air for safe combustion you will have an explosion.


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## rich_kildow (Feb 7, 2012)

I'll get some pics and serial up when I get home in the next few hours. I'll start by checking all the hoses/tubes for obstructions and cleaning the ignitor and flame sensor while I'm in there. I'll also double check that the fan is seated properly and the gasket is intact. I only plan to jumper it momentarily to diagnose the problem and then immediately find a new pressure switch. We are looking at 15 below the next night or two and I don't really want to be without a furnace. 

Does the gas valve make a pretty good clunk when the solenoid opens? I know it is significantly larger than the solenoids in welders so I would imagine there is a significant "click" when it opens.


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## yuri (Nov 29, 2008)

DO NOT touch the igniter as it is very fragile and will burn out quick if you get oil from your fingers on it. they can make a pretty good clunk, mine does and actually they are a redundant valve with 2 seats.


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## rich_kildow (Feb 7, 2012)

Understood. Same here on the gas valve as far as 2 seats. I'm home and am about to check stuff out so wish me luck. We're already below zero and the sun's just going down.


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## rich_kildow (Feb 7, 2012)

Well, whatever it is is intermittent. I got home and the house was down to 59 with the LED blinking once indicating it was in lockout mode. I had reset the breaker this morning before going to work and it was already in its cool down program from the thermostat, so it tried to recover before we got home and couldn't start. I opened the upper cabinet and flipped the breaker for 30 seconds and when I turned it back on, it fired right up beautifully. So whatever this is is intermittent and occurring after the ignitor heats up. This is from the service manual:

The normal operational sequence in heating mode is as follows:
1. R and W thermostat contacts close, initiating a call for
heat.
2. Integrated control module performs safety circuit checks.
3. Induced draft blower is energized causing pressure switch
contacts to close. Humidifier terminals are energized with
induced draft blower.
4. Ignitor warm up begins upon close of pressure switch
contacts.
5. Gas valve opens at end of ignitor warm up period, delivering
gas to burners and establishing flame.
6. Integrated control module monitors flame presence. Gas
valve will remain open only if flame is sensed.
7. Circulator blower is energized on heat speed following a
fixed thirty second blower on delay. Electronic air cleaner
terminals are energized with circulator blower.
8. Furnace runs, integrated control module monitors safety
circuits continuously.
9. R and W thermostat contacts open, completing the call
for heat.
10. Gas valve closes, extinguishing flame.
11. Induced draft blower is de-energized following a fifteen
second post purge. Humidifier terminals are de-energized.
12. Circulator blower is de-energized following a selectable
heat off delay period (60, 90, 120, or 180 seconds). Electronic
air cleaner terminals are de-energized.
13. Furnace awaits next call from thermostat.

Remember that this morning the ignitor would heat but no flame and now that I know what I'm listening for, no click of the gas valve opening. Based on the operations if the ignitor heated up, the pressure switch must have been good, so it must be the gas valve or control board, right? I'll look through the manual to see if this is something I can test but am I better off getting one of these parts replaced ASAP?


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## yuri (Nov 29, 2008)

Intermittent problems are the worst. NO point in parts changing as that is expensive and does not work too well. As a tech I will put my meter on the gas valve with alligator clips and cycle the furnace on/off about 25X in a row with the door switch. If a gas valve is sticking it usually shows up as the odds are good. should get 24 volts at the valve, if none then the board is bad, if you got 24 volts and the valve does not open then it is bad.


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## rich_kildow (Feb 7, 2012)

I think I understand, but let me make sure I have this. Hook up a meter on the gas valve to check for 24V and cycle the furnace until I get a failure to ignite like I've been having. If there is voltage at the valve when it fails, then its a valve. If it fails with no voltage to the valve, then its the board.

It's still running perfectly after that initial breaker flip got it going over 30 minutes ago, so its capable of running for extended periods and this is definitely something in the startup sequence.

*EDIT* It just shut down 5 degrees below the set point and went into its retry mode after it failed to reignite, same as this morning.


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## yuri (Nov 29, 2008)

You got it. :thumbsup:
If a furnace runs 25X in a day it usually fails once a day when intermittent problems start and then gets more frequent. You can simulate that with my method and 90% of the time it works. other than that you got to wait till it fails completely and it is good to have some backup 1500 watt heaters.


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## rich_kildow (Feb 7, 2012)

Well, I didn't see this one coming. After the last shut down I tore into it: the fan and gasket were seated properly, all connection in the upper chamber were on well, no obvious corrosion but I know that doesn't mean anything for sure, pulled the tube off the draft induction motor and blew GENTLY in it and the switch clicked, replaced the tube and moved to the tube going to the box behind the motor (I don't know the proper name). Pulled the tube and water started flowing out. And by water I mean 4 or 5 big balls of paper towel to catch it all. The switch clicked, replaced the tube, and it fired right up. 

I'm guessing that box isn't draining properly (I'll figure out where) and fills with enough water to block the tube going to the not-the-draft-motor pressure switch, killing the furnace. Water drains slowly/evaporates over time, and the furnace is able to light until enough water builds up and kills it again via the pressure switch. 

But shouldn't this not allow the ignitor to heat?


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## yuri (Nov 29, 2008)

Post some pics of it with both doors off as it is impossible to tell what you are seeing. There is a condensate trap where water drains into and then goes out of the furnace into a floor drain or pump. That trap may need to be removed and flushed with hot water and bleach. If it does not drain then water backs up into the secondary heat exchanger and prevents the pressure switch from closing. Click on Go Advanced> manage attachments and post some pics.


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## rich_kildow (Feb 7, 2012)

Here's the overall of the upper cabinet. 










The hose that water was draining from is the grey tube that goes from the lower right of the box behind the draft induction motor and cuts up and left behind the large drain hose from the PVC exhaust and in front of the white thermostat wire. I assume there's an obstruction in the black drain hose on the left that leaves the other corner of that box.


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## yuri (Nov 29, 2008)

Yep, there should be a condensate trap on the left of the furnace which needs cleaning or the drain hose from it to the floor drain is kinked or plugged with algae.


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## rich_kildow (Feb 7, 2012)

Sounds good. I can see where some water had been dripping from where the draft motor attaches to that box. It looks like this was sealed with black RTV type silicone in the past. Is there a gasket for this or just replace it with silicone?


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## yuri (Nov 29, 2008)

my neighbor has a similar Goodman. in the summer I took a hair dryer/heat gun and dried it quickly and then used RTV silicone. hard to do in the winter when it gets wet and running as the silicone won't cure. silicone works fine but it needs time to cure and summer is the best for that job.


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## rich_kildow (Feb 7, 2012)

I have a bunch of cork rubber gasket material that is something like 1/8" thick. Would that work?


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## yuri (Nov 29, 2008)

I would not. the factory gasket is rubber or may even be a special order large rubber O ring. if you can seal it externally do that and sometimes those leaks stop themselves over time with water mineral. if it ain't broke don't be fixin it is my motto, or you may make it worse.


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## rich_kildow (Feb 7, 2012)

The drain tube from the box behind the induction motor was completely stopped up with algae. I removed it and ran hot water in the direction it usually flows and it actually held water without dripping. It's all cleaned out and bleached, so hopefully this will fix it.


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## yuri (Nov 29, 2008)

the box is called a collector box. clean the condensate trap also.


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## rich_kildow (Feb 7, 2012)

It's running great! I scrubbed everything out and will run bleach through it periodically to keep the growth down.


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## TreAdidas (Dec 25, 2015)

rich_kildow said:


> The drain tube from the box behind the induction motor was completely stopped up with algae. I removed it and ran hot water in the direction it usually flows and it actually held water without dripping. It's all cleaned out and bleached, so hopefully this will fix it.


Signed up just to say thank you! Have an Amana Air Command 90 furnace that was experiencing this intermittent on and off igniting thing. Same exact problem. Drain tubes were completely stopped up. A quick little flush with bleach, warm water and a quick clearing with a shop vac and we were back in business. Whole repair took all of 25 minutes due to your help, on Christmas Eve no less! 

Thx!


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## rich_kildow (Feb 7, 2012)

Glad to hear it!


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## bnich64 (Dec 5, 2020)

rich_kildow said:


> It's running great! I scrubbed everything out and will run bleach through it periodically to keep the growth down.


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## bnich64 (Dec 5, 2020)

rich_kildow said:


> Glad to hear it!


I have the same furnace, after I read this I cleaned the tubes going into the pump, they were both filled with algae, like a month later havent had a problem, everything working as normal. thanks for the info.

PS: I had maintenance 3 weeks before, I guess that was a waste of money. they sure do want me to buy a new unit.


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