If your igniter comes on but no ignition, that eliminates the possibility of a bad or clogged pressure switch, high limit or flame rollout switch. Sounds to me like you have a control board, or a gas valve going bad. Could even be some loose, corroded, or faulty wiring. Before the igniter comes on the furnace does a self diagnostics to ensure everything is working, or the furnace will not make it to the igniter sequence. Inducer motor, pressure switch/s, limit controls are closed…then comes on the ignitier, gas valve opens, pilot runners and burners ignite, flame sensor detects the flame, blower comes on and all operations are working.
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It sounds like the ignitor is not working, Since the heater is not detecting a flame it goes to lockout. Check the ignitor wiring to see if it is in good shape. Sometimes the connection where the wire (from the IID) connects to the ignitor gets corroded.
It could also be the IID which makes sure the safety loop is complete before calling for heat and sending current to the ignitor. Good luck with it.
Sounds like your ignitor is bad, not lighting the gas. If this happens 3x, then controler goes into lockout and induced draft motor continues to run to extract the gas fumes as a safety. Either replace the HSI (Hot Surface Ignitor) or sand down the end of the electronic spark ignitor and it's ground rod (they work like an exposed spark plug) to remove the carbon buildup on it so it can spark again. All with the power off, of course! If you need more help, please ask, I'm glad to help! 25 year HVAC service Tech- residential & commercial systems.
This furnace should have a trobleshooting diagnostic led flashing light. Each blink (for example 3 blinks means open limit switch) has a particlur meaning. On the bottom panel has an explaination on what the blinks mean. But in the meantime check 24v at the gas right as the ignitors light. If you have 24v and the gas valve doesnt let the gas thru then the gas valve might be defective. I usually put 24v dircetly to the gas valve for 2-3 seconds to see if gas will come out. It is loud enogh to hear as well as smell. If you dont have 24v as the ignitor tries to light then check the air pressure switch. Also follow the wire off the gas valve. One is to ground. Make sure the gas valve is grounded. Follow not the grounded wire but the other one. Find out where the 24v power stops.
Check to see that the pilot is lit if it is a standing pilot. If not check to see the the ignitor is glowing up or the spark ignitor is working when the furnace first trys to start. If it is a newer furnace check to see if there is a flash code in the bottom blower section on the board. There will be an led light that will flash a designated number of times depending on the problem. Once you have the code remove the door abd see if there is a chart on the back for the flash code.
Check out the green wire going to the gas valve for proper ground,and also check all wires for good connections......... for the intermitting start / stopping and sand the fame sensor pin, this should do the trick.
Count the flashes before a pause. A steady on is bad ground or loose igniter. 2 flashes is either low gas pressure, bad flame sensor, gas valve wires loose or bad ignitor. 3 flashes is a bad pressure switch, or blocked vent. 4 flashes is a bad roll-out switch or open contact. 5 flashes is bad wiring to gas valve or flame sensor, 6 flashes is either a bad control board or bad thermostat.
OK, if the furnace is not lighting for even a few seconds, you have either a bad gas valve, bad wire, bad control module or no gas. The pressure switch is not the issue. Check all wires to the gas valve and look for 24 volts across them when the ignitor glows and you hear the click. Then test for 24 volts to ground. It could be a bad ground wire.