Amana gas furnace intermittent problem

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Old 12-22-10, 05:14 AM
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Amana gas furnace intermittent problem

A little background first. I just bought a house that has an amana gas furnace. (will have to get back later with the model number) We are not staying in it until everything works. I do a little each night after work. The house sat empty for 2 years. The gas company turned on the gas and started the furnace and told us we were lucky it worked after that long. The furnace heated good for 2 days, that evening the house was cold when I got there. I turned the power switch off then back on. The induction fan came on, the hsi came on and glowed good, the valve clicked and I heard hissing for a few seconds then the valve clicked and the hissing quit and the hsi went out. I shut it down and repeated and it fired up the second try. The furnace works for a day or 2 and does it again. (ff a week) I spent the night there last night and I had to get up every hour and a half and turn the power of and back on. It would light when I did that but not light on its own. Any ideas? HSI? flame sensor? Gas valve? something different? Much thanks in advance.
 
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Old 12-22-10, 08:29 AM
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Something is shutting the furnace off. It might be the thermostat or pressure switch or a bad circuit board/ignition module.

Do you have an AC voltmeter and understand how to use it?
 
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Old 12-22-10, 09:00 AM
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Yes. I have a vom but don't have any specs for the furnace. I am going to get the model number in an hour. and restart it so my pipes don't freeze.
 
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Old 12-22-10, 10:39 AM
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Check to be sure that it's not the thermostat shutting off the burners. Look for a steady, uninterrupted 24 VAC voltage at the W terminal when the furnace shuts off when it shouldn't. If the 24 VAC stays on, that's not the problem.

Similarly, check to be sure that the pressure switch isn't opening and shutting off the furnace. It should stay closed as long as the inducer motor is running.

Lastly, check to see if the 24 VAC at the electric gas valve is shutting off when the burners shut off.


Are you getting any diagnostic lights signaling a problem? If so, what is the diagnostic message?
 
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Old 12-22-10, 10:51 AM
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Went and checked at lunch, it is working and warm in the house the model is GHI90A30 and it was manufactured 08-05-88. It will be this evening before I can check the voltages. Will do that and get back later. Thanks for the help so far.
 
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Old 12-22-10, 10:55 AM
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You can do the checks I described whenever the furnace has quit running when it shouldn't.

Actually, if the inducer motor is running, you know the thermostat is calling for heat. So checking for the voltage isn't really necessary if the inducer motor is going.
 
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Old 12-22-10, 11:45 AM
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The inducer motor runs continually. Once the thermostat calls for heat the inducer motor comes on. A minute or so later the hot surface igniter glows bright orange, after 15 or 20 seconds the gas valve clicks and i assume the gas is flowing, the hsi goes out, the hissing stops and the inducer motor keeps going. After another minute or so it repeats the cycle, if it doesn't light the second time the inducer just runs and runs until i turn the power off(reset) then when I turn it on it does the same process again. I have noticed that if it doesn't light the first time and I wait for the gas valve to open then blow the gas towards the hsi it will light. Don't know if it would light without me doing that or not but it sure is aggravating. Had to restart it all night long then today it runs.
 
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Old 12-22-10, 02:08 PM
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You need to verify that the main burner gas is turned on.

If so, either the hot surface ignitor isn;t getting hot enough to light the gas or the burners are dirty or impaired in some way that prevents them from lighting.

More than likely, the HSI is failing and needs to be replaced.
 
 

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