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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On that thermostat there is an R and an RC wire connection, the R is the power wire for heat and RC is the power wire for cooling. If you connected the power wire (normally red in color) to the RC only the fan control and AC control will work, there has to be a jumper wire between the R and RC terminals (assuming there is only one control transformer) for both the heat and cool functions to work.
Turn the fan in the ON position to verify you have power to the furnace. If the fan turns on, turn it back to AUTO. Pull the thermostat off the wall to get to the low voltage wiring. If you have a gas furnace, pull the red & white wires off and pinch them together. If the furnace starts, the thermostat is bad. If it doesn't start, then begin looking for flame roll out switches in the furnace burner compartment to manually reset. If the furnace inducer (combustion motor starts, & you get no flame, then it is either an ignition problem, or someone didn't pay their gas bill. :0
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
you need to bypass the thermostat wire it jumper wires. in other words jump the wires till the furnace comes on. there are 18 volts at the thermostst. listen for it to click. and set fan to [auto] always
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.