First time poster (Great site BTW.) I have a Tempstar; Model # NTG3100GFA4 furnace that sometimes will take 5 or 10 mins before it starts, here is what happens.
The gas valve solenoid thumps open, the vent fan spools up, the ignitor flame comes on but the burners don't light.
This sequence of events will continue to repeat for sometimes 5 or 10 mins until the furnace finally lights.
I do not have to cycle power for it to light and this problem doesn't happen all the time. I had a tech out yesterday who fully cycled it 6 times and it never failed while he was there.. (Of course.. it would never fail while the tech was there.)
Now my house has 2 of these units one for upstairs and one for downstairs both mounted horizontally next to each other in the attic and easily accessible so I was thinking of playing part switcheroo until I got the problem to follow the part, any ideas where to start? I was thinking control board but would like to here from the experts before I start.
Biggest problem I've had with most of these was the Honeywell (not so) Smart Gas Valve. They have the ignitor circuit board inside the plastic
of the gas valve that for some reason, the soldier joints get corroded or come loose, I've fixed several by sticking a screw between the connector and the beige plastic until I could get another valve or install a new, better furnace.
If you, when it's trying to fire up, just bend the plastic connector a little,
see if doesn't light up, or make a change in the problem.