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Old 02-14-2014, 07:52 AM   #1
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Amana Air command 90 pressure switch


My furnace has the red light blinking 3x, which indicates a stuck pressure switch. I read through some suggestions on how to fix this problem on forums like this and largely it seems blowing through the hose connecting the switch to the induction fan motor helped a lot of people. I tried this and blowing/sucking the tube going to the switch operates/clicks the switch easily, but it didn't fix the problem. Connecting the tube back to the fan motor and removing it from the switch and then blowing into the fan also was fairly clear. There was no water coming out of the tube. I still get the blinking light and no heat. My furnace model, the Air Command 90, only has the one red rubber tube on the pressure switch, I've read others' models have two.

Any ideas? Do I just have a bad switch you think?

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Old 02-14-2014, 08:53 AM   #2
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check your plastic vent pipes for snow or ice or obstructions.

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Old 02-15-2014, 08:32 AM   #3
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Amana Air command 90 pressure switch


I crawled up there today, the vent pipe is clear, I can blow into it, no pressure or obvious obstructions. Still, no go. Switch still clicks easily, but I still get the blinking light, even after shutting the power off for long periods of time. This has happened before in years past but it seemed to resolve itself. The furnace has been running all winter, since Oct/Nov and absolutely no trouble until now. Puzzled.
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Old 02-15-2014, 09:25 AM   #4
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Could be a bad switch, of inducer not running at full speed, or a bad heat exchanger.
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Old 02-15-2014, 09:33 AM   #5
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Only way to know is to put a manometer on the switch hose and see if there is enough vacuum on it. need to know the "WC rating of the switch also. if it is not on the switch/label then a tech needs to get it from Amana.
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Old 02-15-2014, 07:29 PM   #6
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did you try cleaning the small port on inducer motor where hose connects to...ben sr
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Old 02-15-2014, 10:51 PM   #7
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Quote:
Originally Posted by ben's plumbing View Post
did you try cleaning the small port on inducer motor where hose connects to...ben sr
No I didn't "clean" it necessarily, however I did blow through the hose into it, and there was free flow of air indicating (to me) no obstructions.

What do you recommend as far as cleaning? Stick a paper clip in it to make sure there's no obstructions or somethiong more involved?

I'd hate to buy a new pressure switch to find out that's not it...
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Old 02-16-2014, 08:26 AM   #8
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paper clip but a small drill bit is better.
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Old 02-20-2014, 03:48 PM   #9
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Amana Air command 90 pressure switch


I tried cleaning the port on the induction blower where the hose connects from the pressure switch- it was open, no obstructions.

So, with little other options I unbolted the 4 screws that mount the induction blower. I pulled the blower away from the unit and reached around behind it to see if the fins would spin. There were quite hard to spin at first, but not quite "seized", especially since all I had to work with were my finger tips (bending my fingers around the back side of the blower). After I spun it a couple laps it freed up more and more, until it moved quite freely.

Wondering if this was all it needed I held the blower back to the unit tightly (without replacing the screws, just in case) and flipped the on switch and pushed in the door safety button.... the blower fired up immediately. So I put the 4 screws back in and put the panels on and fired her up and it has worked great ever since. So apparently my "stuck pressure switch" wasn't really stuck, it just wasn't moving because of the induction blower not wanting to spin. Why, I don't know, but the above helped to free it.

Thanks to all for your ideas. Since NO ONE suggested simply buying a new pressure switch I figured that wasn't the cause of my trouble, and I'm glad!
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Old 02-20-2014, 03:53 PM   #10
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your problem is your inducer is slowing down ( seizing bearings and normal ) and not producing enough suction to close the pressure switch. with a manometer that would show up. need a new inducer soon.
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Old 02-20-2014, 04:00 PM   #11
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Quote:
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your problem is your inducer is slowing down ( seizing bearings and normal ) and not producing enough suction to close the pressure switch. with a manometer that would show up. need a new inducer soon.
Thanks yuri. I was wondering if this was the beginning of a problem with this. At least now I know what it is.
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Old 02-20-2014, 05:53 PM   #12
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a drop of 100 rpm on those is enough to trip the pressure switch and the bearings do wear and get tighter. at that price point you don't get lifetime quality bearings either.
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Old 02-20-2014, 07:48 PM   #13
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there should be two oiler holes on top of the motor.Get some electric motor or turbin oil and add a few drops in each hole.I've been able to bring a few of these back to life in the middle of the night with a little oil and manually spinning the motor till it spins freely.
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Old 02-20-2014, 07:58 PM   #14
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Thanks HVACTECH96, great advice. I'll do that. Anyone have any idea what those motors run, average? Central MI. I could Google it but that's not always as easy you'd think when looking for a specific part like that...

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