Heating start up problems

JANITROL DEPENDABLE NINETY TWO FURNACE-HELP!!!!!!!! PLEASE?
I moved into a house that needed a (bit of work) this past march 08...the house has a Janitrol dependable ninety two furnace. (Model number-GMN080-4)

when I first fired it up ran great...used it clear up to june 08'...and then I just turned the theromostat down and turned off the fan and forgot all about it ....nerver turned the gas off or the main power..didn't think I needed to.

yesterday I went down in the basement, checked everything out, visually everything looked ok, gas was on, power at switch was on, so I came back upstairs tured on the fan and raised the temp level to about 75.....I heard the fan kick on, however no heat.

I went back down and started fiddling around..nothing...I called a friend who works for a heating company....he installs systems...(not a service tech) he noticed that there was a little red flashing light....the light was blicking three times .....according to the troubleshooting guide on the inside panel this indicated that

pressure switch failure to close..and sugessted to check venter pressure switch vent blockage

so we took the pressure switch off..checked for blockage..replaced it....tried to fire furnace....it seemed to take off normally....only this time the ignitor came on , glowing orange....but the gas valve never opened....(note:on my pressure switch..there are only two orange wires ...one on the common, and one on a prong marked no)

my friend went back to his place of work and found a switch on another unit from an old job, that looked basically the same and brought it back.....on this switch it had three wires...male prongs marked c, nc, and no.....we hooked it up and tried again...this time the fan kicked on, then we heard some clicking as the ignitor came on, then the gas valve opened and poof...we had heat...yeah!!!!!.....so I thought.

he left, then I left for diner, when I came back....the fan was running...but no heat, and the house was cool, so I knew it had not run very long after I left...I went back downstairs...tried to get to fire...nothing.

however I was playing with the pressure switch.....I pulled the wire on the common post....it took off like it should....again short lived..so I switched the wires around on the switch since there is no distinctive markings to signify which was which(there both orange).....anyway again same as above it fired but briefly......

tonight we messed with it again..only this time we got the three blicks code...pulled the vent tube..it was clear...the fan was blowing strong.....
got it to take off..only this time the ignitor would come on but the gas valve never did open......and we got no heat...we got nothing...if any one is familiar with this brand of furnace..and can understand what may be happening..i need your help before it gets to cold....thank you.


Wow a lot of info for a change I appreciate that. Anyway it sounds like you have a problem with the way your pressure switch is working but the trick is you have a 90 plus furnace and there are a lot of things that can make a pressure switch fail to close on a 90 plus. You need to make sure the drainage system is clear as water in the heat exchanger will cause the symptoms you describe. also you need to make sure the venting is clear all the way to the outside of the house. Then you need to check the draft inducer to make sure it is running properly and the blower wheel is intact, I know that is a lot to think about but if it was easy everyone would do it.
no were the tube goes into the induction motor take a wire and clear the trash thats in there blocking also check flue pipe make sure you dont have a birds nest in there you are on the right track but you need to make sure it has a way to vent.