furnace

[godsmacker]

I have a furnance question, any advice would be great!
The furnace only blows cold air. I started it today, and after 10 mins it finally ignited and got really hot but only blew cold air. I think I might have a faulty ignitor, but how would that affect the cold air being blown.

[archblackmage]

It sounds to me like it could be some electrical safety for the furance that might be caused by the flue dumbing because of an obstuction or maybe a cracked heat exchanger, it could also just be a faluty switch or something be cloged or dirty. write out a sequence of events for the start up of the furance so you know what has to proof before the furance runs. cracked hot surface ignigters with a crack in them will provide a situation kinda like your but I would sugest the sequence or events and a ladder diagram would really help you understand your furance and trouble shooting it better.

archblackmage@yahoo.com.
Sunny D HVAC

[dietz]

The sequence of operation is this: call for heat, then the inducer motor starts proves the pressure switch, checks through all the limits, ignitor comes on, flame sensor or flame rod proves pilot, opens gas valve, and flame comes on, warms heatex and either a timer on the board or a limit then makes and turns the blower on.
Where is your sequence stoping ?