Heater no longer works on auto fan, only manual fan
Installed a Honeywell RTH6300B thermostat app 4 months ago. Have a Lennox G20 series Gas furnace. All was working well till last week, smelt funny smell (smelt electrical) and since then the auto fan setting on thermostat will not start fan. Furnace starts but stops without the fan running. Switch to manual fan and evrything works well.
After studying the Lennox manual, could it possibly be the BCC (blower control board that has burnt out) Just a stab in the dark. Appreciate any help I can get
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Re: Heater no longer works on auto fan, only manual fan
When you call for fan in auto ensure your getting 24 volts at pin on control board, if it is not energizing then there is a problem with the relay.. Before you change out the expensive control board, try the therm..
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I had this same problem with my 6300B thermostat. I did not see this when I installed the tstat and did setup for it the first time. If you go to page 16 of the install guide, there are instructions for setting up your tstat for your furnace and AC. The setting I had wrong was on page 20 of the guide. It defaults to a setting for a furnace/ac that is less than 90% efficient. When I changed the setting to a furnace that is more than 90% efficient, the fan not turning on or off problem went away. The setting on page 20 should be set to "3" if you have a more than 90% efficient furnace/ac. Hope this helps your problem
At whic step does it sto at and theres your problem. step-1 thermostat calls for heat and vent fan turns on.... step--2 the glow plug or hsi lights ... step-3the main gas valve comes on and heats the box...step-4 when the box heats up it closes a temp. switch to start the main fan motor!
Most of the Lennox G-16s that I have repaired were having problems with the gray Penn-Johnson Piggyback igniton control module.
This is best repaired by replacing the spark module. Sometimes it may be neccesary to replace the gas valve also. Lennox updated to a ROBERTSHAW ignition system. Honeywell can also be used.
Also check that there is no water in the pressure switch or tube.
Hope this helps.
I currently have a 2 wire system. I have one red and one white. I hooked the red to the R and the white to the W. I had to go into the system setup using the UP arrow button and the FAN button. The first setting is the 1 setting, and I selected number 2 ( Heating Only ). Then the 5 setting. I selected number 1 ( Gas/oil steam or gravity system ). Then 14 is usually 0 for Fahrenheit. I was just messing around and that is the buttons I used and I tested it. The furnace kicked on and then 10 to 15 secs later the air began to blow through the vents. I hope this works for others who read this.
Is sounds like you wired it correctly, The black is a little unusual perhaps its blue, anyway, try disconnecting the wires from the thermostat and see if it shuts off. If so, then it may need to re calibrated. I will need some more info to help you anymore.