Have HVAC Questions? Ask an HVAC Expert for Answers
Do you have a meter to verify 24v at gas valve when you hear the click ? Also are you sure we have gas to furnace?
Yes limits should all show closed. but igniter should not light if limit is open. Lets check terminals on valve and make sure board is sending voltage to valve.
Furnace always fires on high fire so check between C and HI terminals
On side of gas valve.See below
We should get 24v here when igniter glows and you hear the click
. If you are 100 per cent sure we have good pressure to valve and get 24v , valve is bad. If not, most likely connections or bad board.These valves do fail although they are not as frequent as other parts.
You would need either a manometer or pressure gauge.Just because we have some gas does not verify the necessary 11 to 14" needed .If valve is opening you should at least get a faint smell though even if not enough to ignite.
That is a hard question to answer.Sort of like asking why a light bulb worked last time it was turned on but doesn't now. Parts fail. Things change.Our first step is to determine if we are getting the voltage to the valve and then if we have proper pressure into valve.
If no 24v, board may be failing, if voltage but insufficient pressure a regulator may be failing and if 24v and good pressure, valve is failing.
Let me know what you find.