Shuts off i have a goodman gmnt060-3b the exhaust blower comes on ingniter gets hot ignites then gas for about 4 seconds then shuts off,then repats the same wayled does not flash stays solid,then sometimes works fine any ideas

ignition failure. insure air pressure switch closes, hot surface igniter is getting 120volts. check continuity on hot surface igniter, make sure all gas shut off valves are open and gas valve is turned on. make sure there is no blockage in the exhaust

hot surface igniter may be weak. if it doesnt get hot enough it will not ignite the gas

you need a service person to come out

It sounds like you got a tough one there.When you say the blower starts up and then the igniter comes on are you refering to induced draft motor or main blower. The proper sequence is for the thermostat to call for heat at which point the induced draft motor should come on and run for 30-45 seconds,then the igniter should heat up for a few seconds then gas valve should open and main burner should light. After limit switch reaches set point for fan on ,blower should come on till after heat has reached thermostat setting then burner should go out, and blower run until fan off setting is reached on limit switch. If your furnace is not following this sequence and then not always doing the same thing in the same order,I would recommend that you change out board again. I have had several problems similar to this with Goodman units and all but one time installing new board solved it. That time I did everything I knew to do and talked to factory service techs repeatedly and finally installed new furnace. As far as your question about insulation,. As long as it is fire proof I can't see where it would hurt anything. Sorry I'm not more help. Good luck and thanks.

There is a induced draft motor that will run first to purge the combustion chamber and induce a draft, a pressure switch closes proving an induced draft exists, thus allowing the spark and pilot gas, or hot surface ignitir and gas to pilot rsil and /or burners, a trial period for ignition about 30 seconds each for 3 attempts will be made and if not lit by the 3rd attempt it locks out, requiring a reset of power to unit to reset the module or circuit board etc. 1st see what motors running, is it the flue exhaust motor/induced draft??

Check the air filter.
On a call for heat, the 24 volt thermostat sends a signal to the control module. The control module will indicate a call for heat with a light on the control either blinking or remain solid depending upon model. The inducer (exhaust) blower will purge all gasses from the furnace and pressurize a pressure switch. Once the pressure switch tells the module to continue, the electronic ignition will energize and send 120 volts to the igniter. The igniter will glow and you will be able to see it if viewed thru the small inspection port. Once the igniter gets hot enough, it sends a signal to the module opening up the gas valve (24 volts). Either a pilot will come on or the burner tube will ignite then spread the flame to all burners. Lastly a safety sensor will be looking for a certain temperature within a few seconds and the furnace will continue to operate and the room air blower will turn on in a minute or two.

What could go wrong? The unit will not run if there is no signal from the thermostat (bad thermostat or broken wire), the control module does not sense a signal from the thermostat (bad control), the inducer does not energize (bad motor), the pressure switch does not close (blocked vent piping, bad switch, plugged condensate hose), the igniter does not energize (bad control, bad igniter), the gas valve does not open or there is no gas (bad gas valve, broken wire, no gas), the pilot does not light (dirty pilot), the burner does not light (bad burner, plugged orifice, not enough combustion air), the flame does not spread to each burner (bad flame spreader, dirty flame spreader, more bad burners), the flame safety sensor does not detect flame (dirty or bad flame spreader, bad flame sensor, broken wire, bad control), or the room air blower does not energize (bad fan motor, bad control).

The sequence of events for furnace operation is -

Fan purge for 30-45 seconds. During this time, a pressure switch is actuated by the running of the purge fan, proving the control board the purge fan is running.

After purge and purge prove, the hot surface ignition and or spark begins. After a few second delay, the gas valve will open. The control board then monitors for flame prove through another sensor located near the burners. If there is no flame within 3-5 seconds, the gas valve closes. It will repeat this process, usually 3 times, before it shuts the system down, which requires a power down of the system to reset.

I have seen trash get into the hose between the purge blower and the purge switch. But you could be having other problems.

The whole assembly must be replaced.

The sequence of operation is -

Combustion fan purges the heat exchanger. A pressure switch verifies combustion air fan is running. Usually a 30-45 second purge before the hot surface ignitor glows, or the spark ignition starts.

Gas valve opens after 10-15 seconds and main burners light. Control board monitors for flame and shuts gas valve after 2-3 seconds if main burner does not light.

If burner does not light, some boards repeat this for 3 tries, then locks out and is reset by cycling power.

Air blower comes on after another 30-45 seconds after main burner ignition.

Times may vary based on the specific controller board. A flow chart and timing sequence should be located somewhere on the unit, usually in the fan compartment.

On a call for heat, the 24 volt thermostat sends a signal to the control module. The control module will indicate a call for heat with a light on the control either blinking or remain solid depending upon model. The inducer (exhaust) blower will purge all gasses from the furnace and pressurize a pressure switch. Once the pressure switch tells the module to continue, the electronic ignition will energize and send 120 volts to the igniter. The igniter will glow and you will be able to see it if viewed thru the small inspection port. Once the igniter gets hot enough, it sends a signal to the module opening up the gas valve (24 volts). Either a pilot will come on or the burner tube will ignite then spread the flame to all burners. Lastly a safety sensor will be looking for a certain temperature within a few seconds and the furnace will continue to operate and the room air blower will turn on in a minute or two.

What could go wrong? The unit will not run if there is no signal from the thermostat (bad thermostat or broken wire), the control module does not sense a signal from the thermostat (bad control), the inducer does not energize (bad motor), the pressure switch does not close (blocked vent piping, bad switch, plugged condensate hose), the igniter does not energize (bad control, bad igniter), the gas valve does not open or there is no gas (bad gas valve, broken wire, no gas), the pilot does not light (dirty pilot), the burner does not light (bad burner, plugged orifice, not enough combustion air), the flame does not spread to each burner (bad flame spreader, dirty flame spreader, more bad burners), the flame safety sensor does not detect flame (dirty or bad flame spreader, bad flame sensor, broken wire, bad control), or the room air blower does not energize (bad fan motor, bad control).

goodman furnance the exhaust fan starts, igniter glows hot, all burners lite up & will burn for about a minute and shuts down . I think it senses the room blower does not start so it shuts down.