Neither AC or heater will turn on
 

I have a comfortmaker unit that came new with the house in 2000. My problem is that it neither the AC or the Furnace will cut on by adjusting the thermostat. I can get both to come on IF I go in the attic, cut the power off to the unit, and then cut it back on. If I do that, the furnance and/or AC will run for one cycle, but not again unless I go back in the attic to 'reset' it. Initially, I thought it might be the thermostat, but after I reset it, I can control unit on the initial action after I reset it. Thanks in advance for your help.

To my knowledge, there's no LED to guage what the problem may be. It's possible that I dont know where to look for it though. If I take the cover off, there's no light or anything.

Too many things could cause this for a diy to check without proper training and tools. You should call a tech.