When i try to turn on the furnance it will not come on. The light flashes twice and that says my combustion air switch is stuck closed how do i fix that.
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Steady light on - normal operation.
One flash - ignition failure.
Two flashes - combustion air switch stuck closed.
Three flashes - combustion air switch failed to close.
Four flashes - limit switch open.
Five flashes - gas valve energized with no call for heat.
Rapid flashing - reversed polarity.
Hello, A roll out is a switch that senses the temp near the burners. If the the flame pattern in the burners is abnormal that roll out switch will open and turn off the furnace for safety. You can try cleaning the burners yourself and see if that will fix the problem, make sure you turn off the power and gas to the Furnace when working on it. However, if that does not fix the problem Iw ould call a HVAC technician to inspect the furnace, sometimes it could be low combustion air or a problem with the gas input to the burners.
I have had the same problem with mine for the last 2 years. Remove the motor on the side of the furnace(usually held on by 3 screws) and turn the fan blades inside by hand. after sitting all summer it seems to get stuck. If it moves freely, replace the motor and try to start it again. This fixed mine the last 2 years! Hope this helped.
The combustion air switch is closed by the air pressure from the draft inducer fan. You can check it with a voltmeter. When the heater starts to run check the voltage reading where two wires connect to the switch. It should be 0 vac if the switch is closed. Instead of starting the furnace, you could also remove one end of the rubber hose that goes to it from the draft motor and blow into the hose and see if that closes the switch. It may be just stuck. I almost forgot to mention the most important thing; make sure the draft motor is running. Let me know what you find. The air pressure switch is a safety feature to prevent the furnace from running if there isn't enough air supplied to the burner for proper combustion.
The flame sensor rod should be cleaned, if that doesn't fix it check the combustion air switch. There should be an error code, look for a blinking light and code chart under the filter door.
Check if they have a "sail switch" that senses combustion air flow before allowing fire. These are a small vane in the combustion air intake that moves a microswitch when air is flowing.
31 PRESSURE SWITCH DID NOT CLOSE OR REOPENED - If open longer than five minutes,
inducer shuts off for 15 minutes before retry. Check for: - Excessive wind
- Proper vent sizing - Defective inducer motor
- Low inducer voltage (115VAC) - Defective pressure switch
- Inadequate combustion air supply - Disconnected or obstructed pressure tubing
- Low inlet gas pressure (if LGPS used) - Restricted vent
If it opens during blower on-delay period, blower will come on for the selected blower
off-delay.
33 LIMIT CIRCUIT FAULT - Indicates
This air switch proves that the inducer motor is running and moving air. If not, check to make sure that the inducer motor starts and that the flue is free of restrictions.....eg. bird nest, ice/snow, or some other critter that found a new home.
Try cleaning the flame sensor. Its the most common problem on todays furances. You should clean it with a fine grit sandpaper or emery cloth once a year.
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