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American Standard 5000 gas furnace

19K views 20 replies 6 participants last post by  hvaclover 
#1 ·
I have an AS 5000 gas furnace in my home. It is probably close to 15 years old. It has worked flawlessly up until just a few days ago. It will cycle "on" when told to by the thermostat. I can hear it "click" as it begins to cycle, the ignitor will come on, you can see the glow in the heat tubes and then it will click once or twice more and the glow will deminish. It will do this once or twice with the motor running, but the large blower fan in the bottom compartment will not switch on. The red light on the circuit board begins to blink red, but it simply flashes, no code or sequence. The tage on the board states for a "Flashing Red light, refer to your service manual". As the furnace was installed prior to us moving in 10 years ago, there is no service manual. If I turn the power off to the furnace and then immediately turn it back on again (via a "light swtich" on the side of the furnace near the control board) it will cycle/run just fine and heat the house. On occassion, will will cycle several times in a row as it should, before going back into its non-working/blinking mode.

Does anyone have any ideas what I should be looking at that may be causing this? I am guessing that it is a sensor or switch that has worn out, but I am not sure. The filter is brand new and I have even repalced the thermostat. I would rather not have to spend the $$ on a service call if I dont have to.

Thanks for all the help.
 
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#2 ·
Can you measure for 24VAC to the gas valve when you hear a click after the hot surface ignitor glows?

What is the model number listed inside the burner section of the furnace?
I may be able to post a manual.

If no trouble code appears with these symptoms, it points to the board.
 
#3 ·
Thank Houston, I appreciate all the help I can get.

The furnace is model: TUC100B948AC
The serial number is: F30545736

The light flash's in no sequence. it simply blinks for however long it is allowed to until I reset it either by turning the power on and off at the switch, or by the cover switch for the lower half that houses the blower motor.

I have no way of measuringthe VAC pressure.

Thanks again.
 
#5 ·
Go to Sears or HDepot, Radio Shack and buy a inexpensive electrical multitester. A good one can be had for under $100. Cheaper than a service call.
Is it a high efficiency furnace with plastic vent pipes or a mid efficiency one with a metal pipe to the chimney?
 
#7 ·
For a model number, lets try changing the last character from a "C" to an "0", or TUC100B948A0.

It is a high efficiency furnace with a plastic vent pipe directly out the side of the house.

I'll have a volt tester later this evening and then will have to figure it out.

Here is a pic of the furnace unit if it helps any.

Thanks again.
 

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#15 ·
Turns out mine was nothing more than a dirty, and starting to crack, heat exchanger. Cleaned that up, as well as arond the sensors and pump and all works fine. Had a furnace company come out and recheck and all was good, except the cracked heat exchanger. Tried to sell me a new furnace for $5200.00. So far, furnace is working great this year, no issues and still havent replaced it. When I do, should cost me around $2,000.00, through a different company.
 
#19 ·
I had posted in '09 that there's a recall bulletin on the heat exchanger of your furnace.

By your own admission you know you have a crack in a furnace the factory warned owners about.

Cracks don't get smaller and you cant rely a CO detector to save your life.
 
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