I have a Day n Night gas furnace. The blower seems to be working as expected but the gas does not light up. I cleaned the filter which was extremely dirty. Any thoughts? Thanks.

Does it have a pilot lite? Or a electronic igniter?
Is the pilot lite/igniter working ?
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More info is needed ,tell us all you can about your furnace, along with the model number could help

It is Day n Night Model 383KAV048075 Series B made in 1993.

I ran a self check and it only went through step A (Inducer Relay) then skipped steps B and C (Igniter Relay and Humidifier Relay) and then did Step D (Blower on).

I checked the blade fuse and it is fine. There is 24+V on the secondary side.

I do not smell any gas and the heat does not come on. The blower seems to work.

Any help will be appreciated. I am pretty mechanical but have not worked on this problem before.

On start up
1st inducer starts and runs
2nd igniter comes on (should see it glowing)
3rd gas valve opens and burners fire up
4th after about 90 seconds blower comes on

Very carefully (they are fragile) check igniter ,if it plugs up you can check continuity of igniter,or sometimes just look for any breaks or lighter grey area that shouldn`t be there tells you its in need of replacement

Igniter does not come on. It stays cold. I will try to check voltage across it. Should it be 24V?

Unplug the igniter and check for 120v across the supply wires. If you are getting that voltage, it means your igniter is bad. You can also unplug the igniter and test for continuity across the actuall igniter wires, if no cont, its bad. Let us know what you find.

With the furnace door switch taped closed use a jumper wire and jump from R to W on the furnace control board. What works? If you have a noticeable white spot or crack on the black part of the igniter(element). Its bad. You can get one at any local hvac company.