Older Carrier gas furnace Blower stays on.


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Old 01-22-13, 03:26 PM
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Older Carrier gas furnace Blower stays on.

I am new to this so please be patient.

My Carrier Gas Forced Air Furnace blower stays on all the time. I took out the limit "switch" 3 inch probe that has two wires attached to its terminals, and the blower still runs.

Any suggestions. I have 24 volts (actually 26.4 v) at the R terminal (between R and C).
 
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Old 01-22-13, 05:39 PM
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If you have 24 VAC at the R terminal as your describe, that eliminates one class of problems which can cause the furnace fan to run continuously.

Does the furnace provide heat?

Post the model number of the furnace, which can be founf on the rating plate in the burner compartment of the furnace.

If the G terminal on the circuit board is energized with 24 VAC, the fan will run continuously. See if you have voltage on that terminal which could come from the thermostat or another wire attached to the G terminal.
 
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Old 01-22-13, 05:41 PM
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Post the model number.

Does it have a G terminal? Is it jumpered to R or connected to anything?

Does it operate properly otherwise? - ie burners cycle on and off as they're supposed to.

Does the limit look like this?


If yes, pull the white peg.
 
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Old 01-22-13, 07:22 PM
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Yes, the furnace provides heat fine. Model No. 394GAD000125

I don't see a G terminal. There is only a C terminal (with not wires attached) and an R and a W, R and W have the red and white thermostat wires attached.
 
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Old 01-22-13, 07:26 PM
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Yes it operates properly otherwise.
No, there is no limit switch or box like you show. Only a 3" probe that is inside the air duct chamber above the burners and it has two wires attached to it that go to the circuit panel.
 
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Old 01-23-13, 12:37 AM
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Here's the manual for your furnace - http://www.xpedio.carrier.com/idc/gr...i394g-25-1.pdf

Unless that furnace has a continuous fan option (no reference to that in the manual), the board is bad.

It's very old - the board probably isn't made any more, and heat exchanger likely to be cracked. Call a pro to check it or better yet, consider replacement.
 
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Old 01-23-13, 12:24 PM
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The circuit board which is in the fan compartment has an electronic timer to shut off the fan. That timer is bad, and the circuit board needs replacement to correct the problem.
 
 

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