I have a Unicell 90 gas furnace. The furnace turns on but does not blow out any air. I checked the ignitor since that went had to be replaced last year, but it looks fine. When I turn the thermostat to fan, cool air comes out of the vents. As soon as I put the thermostat on auto, the air stops blowing out. I also hit the reset switch a few times and cooler air blew out for a short while when the thermo. Was on auto but stopped. Any help would be greatly appreciated. I have a technician coming later on to look at it but I like to be armed with information so that I'm not totally at their mercy.

Sounds like you possibly have a negative,untrusting ,unhealthy attitude before the technician even gets there. I doubt we could educate you with all you need to know before he gets there.If you tell him what's wrong,before he gets a chance to check things out ,chances are he will fix just what you told him to fix and do nothing else, which could be bad for you. A reputable technician will /should stand behind his work.if he make a bad call he will correct it. If you make a bad call, you will have to pay the piper. Just something to think about

I actually ended up buying a new furnace because a camera shot showed a crack in my heat exchanger. My attitude about wanting to be somewhat informed on a possible problem wasn't "unhealthy," it was smart. As an intelligent consumer, I feel it is my duty to at least have an idea about a problem whether it be with a vehicle or something in my home. Otherwise, you leave yourself open to be taken advantage of. In a utopian society, every technician would be trustworthy and honest but let's be real, that is not reality.