On cold demanding days, my Goodman GMNT gas furnace operates fine for about 20 minutes, then goes into a lockout for 60 minutes (LED blinks once). If I set the thermostat low (so the unit can meet the demand) the system shuts down normal (not locked out and steady LED). The flame sensor has been cleaned (sanded, not replaced), the RO switches are OK, the vent pressure switch was replaced (mfg type and not a generic), stack over-temp switch seems good. Gas regulator and pressures seem good. What's causing the unit to go into lock-out mode (according to the mfg literature only the flame sensor 'three time' failure causes this)?
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Sequence of operation for most Gas fired furnaces...
Demand for heat from t-stat
Control board demands combustion chamber purge
(IDM /induced draft motor if it has one)
Control board tests all safeties (this is usually via
the IDM wiring.)
Control board sends 24v to PV at the gas valve igniting
the pilot OR control board sends voltage to the
ignitor as in yours.
Control board sends 24v to MV at the gas valve.
Control board allows time for heat exchanger to warm
then calls for blower operation.
Your sequence of operation? Won't be the flame sensor unless ignion has been achieved. If the ignitor is working/glowing red? Is the IDM working? Make & model#?
sounds like there is a Freon leak and has been since it was installed and is going off on because of low charge, you will need to call a competent A/C repairer, more then likely the leak will be in the air handler, should cost under a $100 to fix. Good Luck Tim
Problem: Your furnace will not ignite the gas to produce heat
for your home. When a furnace has a bad igniter what I see most of the time is
the following sequence of operation:
1. Thermostat calls for
heat. 2. Draft inducer motor starts. 3. Pressure switch attached by a
small plastic or rubber tube senses the negative pressure produced by the draft
inducer and closes. 4. Draft inducer runs for 30 seconds to a minute before
you hear a gas hissing sound. The ignitor did not glow, the flame sensor (a
small metal probe about 1/8" in diameter, with a white porcelain base) does not
sense the flame, so after 8 to 10 seconds the hissing sounds stops with no
ignition of gas to heat your home. Your furnace shuts down and goes into a lock
out condition until you turn your power switch back off and on again. Then the
sequence starts all over again with no ignition of the gas. Solution: You
probably need to purchase and install a new igniter. I would suggest that you
inspect your igniter closely for cracks. Make sure you do not touch the igniter
with your bare hands. If you do not visually see a crack, then you could have a
furnace control board problem or a limit, roll-out switch problem. The furnace's
control board might not be supplying the voltage to the ignitor. If your
furnace lights and the gas stays on for 8 to 10 seconds, then shuts right back
off, then you need to clean your flame sensor with light sand paper or steel
wool. You might need a new flame sensor, but most of the time they can be
cleaned an will work well after cleaning.
Do you have a heat pump? If so this is normal. You are probably used to a gas furnace. There are heat pumps that do have a delay though. Look on the circuit board in the air handler. There may be a set of pins that say 0-30-60-90 yours may be at 0. Also some digital T-stats offer that function for delay off to get the extra heat or cold from the system. Find out what the model number of the air handler and call the Goodman supplier in your area to see if you have these options. If you have a gas furnace and it's not delaying the blower there is definately something wrong.
If the burners do not fully ignite, the sensor will shut the furnace down. The lack of sufficient burner flame is a gas valve or gas pressure problem within the valve. Replacing the gas valve with the original one may get you going. I surely suggest a professional service company for safety reasons and a thorough inspection. A 20 year old furnace is past it's normal life span.
Hi!!! If the flame turns on then off and on then you should change your flame sensor on the gas furnace..YEs flame sensor is shorted..The flame sensor is located by the valve burners it has one wire and is white..Good luck..
1st, take a picture of where each wire goes to. Look in the owners manual for an exploded view of how it goes together. The heat exchanger most likely comes out from the front of the furnace. You will have to remove and reinstall every componant inside the furnace to get it out. Suggestion, replace the whole furnace. It will be cheaper.