I have an aire-flo model # AF90MPB075U2.the heating & cooling does not come on. I checked the 5 amp fuse and is good. I tried using a jumper wire from red to Y & red to W. I get nothing, could this be the transformer?

I had a similar problem with my thermostat a while back, when I replaced it. Apparently if you touch a couple wires together(The ones they tell you not to) if it sparks then you have shorted the transformer and ruined it.

Hope this helps.