Can you verify if 24 v ac is present at gas valve when ignition should occur?
was burner cover on when it faaulted?
With cover off....has burner failed?
and when failed...we mean ignitor glows but flame doesnt light at all?
And out of 10 cycles done, how many times would estimate fault to be?
and after each fault it codes 7?
Do you have a long light or small propane torch?
This is just process of elimination.
Sometimes a glow ignitor doesnt reach 1800 f in order to light gas. It glows but not hot eneough...to eliminate this option we point torch beside the ignitor during start up and see if it lights reliably with torch...understand the point?
removed tube from pressure switch and cleared barbed fitting on furnace where tube attaches
check tube for cracks
no vent blockages
sensor clean with steel wool
None of these are suspect but good things to do as preemptive...
Your issue is either no gas
Or the 2 dont get together.
The part number is(NNN) NNN-NNNN/p>
example - http://www.theignitorstore.com/catalog/york_igniters
Any local heating contractor should have one also.
I wish you luck...and I am available for follow up.