American Standard- TUD100C936A


Old 02-24-04, 04:52 AM
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Smile American Standard- TUD100C936A

This might have been asked before, but we have a gas furnace, see the subject line. No pilot light obviously. It blows warm air for 30 to 60 minutes (sometimes less), then runs cool air. We reset it and it does the same thing.
Filters are changed on routine, but it's been 1.5 yrs. since cleaned. Could this be the problem? I realize I should clean it first to find this out.
Tips on cleaning this furnace are appreciated. The manuals I have are limited on that info.
I would like to fix this myself w/o a service person, but will call one if it comes to that.
Thanks in advance.
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Old 02-24-04, 06:21 AM
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Hello MelloYello. Welcome to the Gas Heating forum & the Do-It-Yourself Web Site.

There could be any number of possible causes for a furnace to cycle off too soon. In order to help us help you, more details need to be known.

Furnace age would be helpful.
What do you mean by reseting it? Reset what?
Does the fan continue to run long after the burners shut down?
Does the room temp ever raise to the thermostat set temp?
Does the unit have A/C? Possible the A/C coils are restricted.
Possible venting problem causing the safety device to shut it down. Or the flame senser is dirty? Solenoid in the gas valve may be defective.

Lots of possibilities. Kindly use the reply button to add more specific and detailed information from which the professionals can determine the cause. Thanks.

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Old 02-24-04, 07:06 AM
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Thank you for the fast response.

The furnace is 12 yrs. old (original w/ the house).

Reseting it after the lock out. At the thermostat - Off, on, off, on within 30 seconds.

Yes, fan continues to run.

Yes, the temp does raise to the thermostat.

No A/C.

Thanks for the other hints too...

It calls for heat for awhile, then stops. When the burners try to re-ignite they'll burn for 5 - 10 seconds..then shut down. The fan continues to run and the light flashes indicating a lock out.
Perhaps I should clean the flame sensor first.
Old 02-24-04, 07:08 AM
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Lockout Causes?

Another question would be, what causes a Lockout?
Old 02-24-04, 09:04 AM
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What kind of igntion does this have?

-Hot Surface Ignitor "HSI" (glows red)

The sensor may need to be clean if there is one.

If there is none, then you may need to replace the HSI, some HSI are used as a sensor. but DO NOT clean it since it will break. If you do get a new one, DO NOT touch the black stuff, it will shorten the life of the ignitor.
Old 02-24-04, 09:20 AM
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There is only a yellow glow.

What is the rollout? It's located on the left side by the 5 burners.

Old 02-24-04, 09:32 AM
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What is the rollout?
It is a saftey switch that will shut off the gas if the flame are rolling out of the heat exchanger.
Old 02-24-04, 10:02 AM
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I think I read to use a steel wool brush or something to clean the sensor? Is that right?

Thanks for your help and patience.
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