Goodman gmn100-4 there is power to the unit. i didnt see a flame. was wondering if it could be the ignitor

Clean your flame sensor with soft wire brush. It is located opposite side of igniter. Builds up with glossy coating and doesn’t sense the flame so it shuts off the gas valve

There are too many reasons for this to happen so we would have to narrow it down. The sequence of operation on a Goodman furnace is usually:
1: Inducer draft motor comes on
2: Hot surface ignitor comes on and glows
3: Gas valve opens, lights burners
4: Flame sensor detects flames
5: Blower comes on

If the inducer motor never came on, then you start looking at power to the unit, thermostat issues, or inducer motor issues. Just a few places to start. Hope this helps!

Hello,sounds like you have a dirty flame sensor. This is a metal rod on the oppositenside of the hot surface ignitor. turn off power to the furnace and remove the flame sensor, then use steel wool and clean the flame sensor and reinstall. Next turn back power to Furnace.

COMMON PROBLEM THE UNIT MAY HAVE A BAD HOT SURFACE IGNITOR .... these often go bad... if you have avolt meter unplug the ignitor and turn heater on see if you are getting 120 volts to ignitor plug...if so then the ignitor is bad and needs replaced....

I cleaned the sensor that was at the the right further most burner on my Goodman and it worked. got the answer to my problem here at fixya. My burner flame only lasted 5 secs before it shut off. Thanks to all who took the time to send me a response.

check for 24vac between wires on gas valve about 5-10 seconds after ignitor starts to glow. If ignitor does not glow, check for 120 vac to ignitor after inducer goes on.
First...sequence of operation..power to W, inducer motor gets 120v and starts, 10-15 seconds later, ignitor gets 120v and glows, 5-10 seconds, gas valve gets 24v and opens, after 3-4 seconds the flame sensor approves flame and unit stays on. If this is not happening, it has to be in this sequence. Which ever is not happening and you do have voltage to that component, that component is bad. If you are getting a error code on board after it tries to light, pay attention to the code. if a 1 lock out code, that just means it tried 3 times and did not recognize a flame.

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

Check the flame sensor near the ignitor....it could just be dirty. Check that first. Check the electrical connections to it. Also, check the flame sensor's position. It must be within the correct proximity of the ignitor to tell the gas valve to open. Make sure the gas is on to the unit.

Goodman gmp075-3 gas furnace and the flame cycles for 4 sec

First we need to understand what is probably happening by understanding how this unit works.
A flame safety senses a flame and if one is not present it shuts off the gas supply. This safety is incorporated to make sure that if the flame goes out for any reason, it doesn't continue to dump gas into the furnace. Because I have no idea what type of sensors this unit uses, can you explain to me what kind of ignitor it has? See if it has a spark, or a hot surface ignitor. The hot surface ignitor will glow very bright white but looks like it's made of ceramic.