Carrier furnace doesn't restart at correct temperature.


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Old 02-21-15, 10:06 AM
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Carrier furnace doesn't restart at correct temperature.

We have an old carrier weather maker. It waits that the room temperatures comes down to 47degres before to starts, when it is on though it works fine until it reaches 64degres and then stops, even if the thermostat is set at 70degres. I tried to set the thermostat at 90degres but it still kicks in only at about 47degres.

We already tried replacing the thermostat, but it still looks like the thermostat is not communicating with the furnace.

any ideas?
Thanks
 
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Old 02-21-15, 10:27 AM
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The furnace should have a blinking LED visable through the door that will help in diagnosis.
The first digit is the number of short flashes and the second digit is the long flashes.

Post your trouble code for better assistance.

Is the air filter clean?
I believe that would be a code 13.
 
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Old 02-21-15, 10:41 AM
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the air filter is clean,
the LED code is 14
 
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Old 02-21-15, 11:34 AM
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Pull the cover off and look on the back. That will tell you what the code is.
 
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Old 02-21-15, 11:40 AM
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Trouble code 14 is ignition lockout.

You need to go down to the furnace. Turn the power off and then back on. Tell us what exactly happens.

I'm going to tell you what I think is happening and then you can correct me.
The draft inducer blower starts.
30 or so seconds later the ignitor glows.
30 or so seconds later the burner lights.
4-5 seconds later the flame shuts off.
 
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Old 02-21-15, 12:56 PM
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so I turned the furnace off and on,
at the first attempt of the furnace to start it did just like you said the flame shuts off but, it tried a second time and this time it is working, and it is heating the house.

The LED error code changed though, it is now 34 instead of 14

And now the furnace won't stop, the thermostat is set at 60degres but the room temp is 70...

...just turned off right now by itself
 

Last edited by carine; 02-21-15 at 01:20 PM. Reason: more info
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Old 02-22-15, 02:54 AM
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I can see one problem and maybe two.

It sounds like your flame sensor rod needs to be cleaned. It is a metal rod that sits IN the flame. It will be held in with a bracket and one screw. Remove the screw and the rod. Clean the rod with a scothbrite pad or steel wool. It needs to be clean and shiny.

As far as the heat not turning off when it should... that would appear to be a thermostat problem.
 
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Old 02-22-15, 06:11 AM
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When it won't shut off can you locate the thermostat wire at the furnace and remove the white wire and see if it shuts off? Likewise if you jump out the R &W wires at the furnace and it starts and runs normal that does point to the Tstat.
Geo
 
 

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