Hello. I have a Bryant 584A (580A) Heating/Cooling unit on the Roof, natural gas, about 18yrs old. In the morning I turn up the thermostat and hear a faint noise but not the click of the ignitor and the heater never comes on. This happened a couple weeks ago and this is the second time. Last time I switched over to AC quickly and then over to heat and it seemed to have "jump started" it and got it going. This time nothing works. Thermostat is a LUX 500. Any ideas? I have the old installation manual that came with it.
Thanks!

Take off the t-stat and jump from r to w, if it still does not work the probem is on the roof.

Ok, when I take the cover off I see wires at G, Y, W, RH, RC. Do I jump W to RH or RC?

Rh will work.

Ok, that doesn't get it going. I still hear the hum of the unit but no clicking of the ignitor. Any ideas where to look on the roof?

Somewhere I saw a post that suggested the pressure tube has water in it? Does this make sense to you?

Well first of all if that does not work, put the stat back on. Then go up on the roof. Take the door off where the burner is. There should be 2 flame sensors. They may need sanded. If there is a power switch up there leave the t-stat on so you can see if the piolit is liting while you are up there. Be sure to turn power off while sanding the sensors

Thanks. I will have a chance to check it out in few hours and will let you know. Hopefully that is all it is!