My pilot light works fine but when the blower kicks on to heat the house, it doesn't bring flame to the burners all the time, sometimes it does and then it doesn't?

There should be a flame sensor mounted on the pilot bracket. This sensor maybe bad or is out of position.

Make sure all wires are connected and the gas is on. Follow the sequence of operation for this model and a few tips on what could be the issue.

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).

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).

Are you saying you lose the pilot flame or the main burner flame? A cracked heat exchanger will cause a "venturi effect" when the blower cycles on. This effect will cause blower to interfere with combustion air and **** out the pilot, and cause lifting of the main burner flames (also add oxygen to the flames changing their color).

Some of your newer style furnaces will kick the hi limit when they have a crack in the exchanger dropping the flame and bringing the blower on.

If you are pretty confident of a crack I would suggest a water test.....After the furnace has cooled. determine which way will most easily access the heat exchanger through the top (under the a-coil) from the "plenium". or from below by removing the blower with it's housing.

once you have determined your approach get a bug sprayer and put water in it. With the heat exchanger cool, use the wand of the sprayer to liberally spray the top of the exchanger. If there is a crack the water will find its way into it. Take a flashlight and look into the bottom of each burner slot, if you see water, you have a crack, shut it down and replace it.

If the hot surface ignitor comes on and fires the burners, and then shuts back down, you need to take a look at the flame sensor. It is a ceramic rod with a metal tip that rests in the pilot flame. When heated from burners, it sends a signal to the main control module, circuit board, which ever this unit is equipped with to keep the burners on. It is a safety to shut the burners down if there is a problem. Take some fine steel wool to clean the metal tip on this and this should take care of the problem. If this does not do it, then 99% of the time you have a faulty control board or module. It will have to be replaced.It is where this flame sensor connects.It will continue to drop out of the circuit, and the fan will start and run. You're T-stat is good or the Hot Surface ignitor would not glow. You will need to take as much info you can from the unit, Goodman and the control, all numbers with you.You can purchase this part at a appliance parts house, or air conditioning parts house. Please keep me informed, I would like to hear back from you. I hope this has given you some direction to follow.Good Luck,
Shastalaker7

Flip the lower panel over and look for a wiring diagram. On that diagram there will be a diagnostic chart. Let me know what 5 blinks represent. Then I want you to read on.

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).

sounds like your pilot saftey is working.the pilot flame heats a device called a thermacoupler which gives a signal to the gas valve letting it know its ok to open main valve. you may need a new thermacouple , might have a dirty pilot orfice or a problem with gas pressure or worse case a cracked heat exchanger in any case in less you have some type of training you should call a pro

If in fact you have the above listed furnace, you do not have a pilot but electronic ignition. You will need to remove the front cover on the furnace, tape down the door safety switch and then have someone help you by turning up your thermostat to a very high setting. Watch and listen inside the furnace. There should be some blinking going on at the control board followed by a small blower fan starting up. Then after 10-15 seconds there should be a click followed by an orange glow viewed thru the viewing window to the burner section. In a few seconds the gas valve should click and the burners will ignite. There is a safety switch that will sense flame and then keep the gas going to the burners. If it does not sense it, it will shut it off within 10 seconds. If all is well so far, your blower will turn on in about 90 seconds after flame. There is a diagnostic code chart on the back side of the access door if you get an error code (blinking) on the control board.

Always check little things like air filter, condensate drain and broken or loose wires.

There are 4 -steps for full run time to kick in a furnace.. step-1, inducer fan runs & prove thru the air tube which closes a switch and tell the circuit board to go to step-2, the igniter lights the pilot & prove its lit by heating the thermocouple, which tells the circuit board to go to step-3, opens the gas valve to dump gas in, which will light from the pilot light, and prove by a flame sensor metal stick on the last burner , which heats up and tell the circuit board Saying, ok , I've got flame.. step-4. when the box heats up, it closes a switch and turn on the main fan...! (Some gas-valves has a brain -or circuit board on top of them and are real sensetive to moisture..)

the flame detector rod is dirty? try cleaning with sand paper and scraping also. there should be a small amp. reading threw wire coming from flame detector rod. in milli amp range. increases when running. some times i use a jumper to hold gas valve on once started to allow time to test amps.