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    navhal's Avatar
    navhal Posts: 1, Reputation: 1
    New Member
    		  
    #1

    Nov 4, 2007, 07:29 PM
    Furnace control board fuse keeps blowing
    Hi,

    I have a Carrier furnace 48GS-036090311TP with a Honeywell T8401C thermostat. I can run the fan on continuously but when I put the Heat to ON on the T-stat, the 5 Amp fuse on the control board (LH33WP003A) in the furnace blows. The sequence is like this:

    1. Fan only operation is running fine
    2. Move the T-stat to "Heat"
    3. The induced fan motor starts to run (for about 3 seconds)
    4. The 5 A fuse blows at just about the time that the ignitor needs to turn on (combustion relay)

    I checked all the wiring connections and they look fine. The lines from the T-stat to the board also appear to be OK.

    The combustion relay resides on the board.

    Could this be a board problem? Or is there a problem with the AC contactor? Or the 24V transformer? I would appreciate it if someone can help me isolate the problem before I spend a few hundred dollars calling the electrician or replacing the board even.

    Thanks,

    :confused:
    hvac1000's Avatar
    hvac1000 Posts: 14,540, Reputation: 435
    Heating & Air Conditioning Expert
    		  
    #2

    Nov 6, 2007, 05:29 PM
    The low voltage wiring might have a short in it.
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