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Re: Furnace gas valve is not opening
YOUR FURNACE IS IN LOCKOUT MODE DUE TO A SAFETY FEATURE OF UNIT. USUALLY THE HIGH LIMIT HAS BEEN TRIPPED, OR YOU PRESSURE SWITCH FROM DRAFT INDUCER MOTOR FAULTY OR PLUGGED. IT WILL CONTINUE LOCKOUT MODE UNTIL THIS IS FIXED.
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Furnace is the term we use for a gas system. I'm assuming you have an electric "air handler"(unit), and or has 1 element staying on, glowing red, and cycling on a limit. These elements are controlled by "heat sequencers", heat relays, and some older units used heat contactor's. This "switch" is stuck closed & must be replaced. I've also seen a direct short at the element itself, where the element has come apart, and a part of that element had touched ground. This completed the circuit and allowed the element the energize. Hope this helps! Its probably a stuck (closed), switch that's supposed to open when the tatat is satisfied.
Depends on the system,if it has 2 wire switch it can be bypassed,but only 1 time for each heating cycle if the system is using i pc board to operate the furnace,sometimes you can take the hose off and lightly suck and blow on it if the switch is stuck,but should have a pro check it,could be a blocked flue pipe or other dangerous problem,and could be a bad switch,did heating and cooling for 30 years
There maybe a few issues. They have multiple safeties on furnaces. With this in mind this process to find the problem would take a Technician to check these safeties. It could be a flame sensor or thermocoupler each senses a flame or heat to keep the gas going. Also the damper for the flue must open for the gas to stay on. There may be more safeties on this and each safety sends a 24 volt current back to control module in order for the gas valve to stay open. If these aren't being met it will try around three times and go into a lock out mode which will keep gas shut off entirely.
· The furnace control checks for an open main limit (this limit is normally closed). If the limit is open, the furnace will remain inoperable until the limit is closed. During an open limit the circulating air blower will be energized. The status light will blink four (4) times. · The room thermostat reacts to a demand for heat.
· The control will then check to insure that the vent pressure switch is open. If, at this point, the vent pressure switch is closed the control will blink two (2) times and will remain inoperable until this situation is corrected.
· The venter blower is energized.· The vent pressure switch will close when it detects a pressure in excess of its setting. If the pressure switch fails to close the status light will flash three (3) times.
The sequence cannot continue until the pressure switch closes.
· After a pre-purge of about ten (10) seconds the electronic ignition device will be energized.
· After a slight delay the gas valve will open.
· The burners will ignite and the flame sensor will detect the presence of flame. The ignition device will deenergize. If the sensor does not detect the burner flame, the gas valve will close and the ignition cycle will be repeated for a total of three attempts. If, after the third attempt, the presence of flame is not detected, the furnace will go into a lockout condition for one (1) hour. It will then repeat the ignition cycle. This one (1) hour lockout and retry will occur indefinitely.
· Thirty (30) seconds after the main valve is energized the circulating air blower will be activated.
· The furnace will remain in operation until the demand for heat is satisfied.
· Once the demand is satisfied the venter will shut off, and the circulating air blower will shut off after the field selectable time off is attained.
· The furnace will remain dormant until the next demand for heat.
It means that the furnace isn't igniting and for safety the control board is preventing the gas valve from opening. Turn off the power to the furnace for a few seconds then observe what the furnace does in heat mode. Some furnaces will run the blower for a minute after you power it back up. After that see if the furnace tries to come on. If you are still getting the code then one of you high temp limit or roll out switches has tripped. Now is the time for a service tech. Make sure that you check you filter and air flow too. Low air flow means the furnace may be over heating. The other thing is the hot surface igniter. Look closely at it with the power off. Do you see a white spot on the element or a crack. If so the HSI is bad. It's an easy replacement but DO NOT touch the carbon element with your fingers and be very careful handling it as it is EXTREMELY fragile.
Try to start the unit again and put your hand on the gas valve and feel if the valve clicks before the ignitor stops glowing , if it does click your valve is bad , I just changed one last Fri. with the same problem