Is the indoor fan blowing out of the furnace? Does it feel like it is a normal amount, velocity??
If YES- Good. If no air is coming out and no sound from the furnace, check the power switch and breaker. If it is bowing but hardly, check and remove the air filter.
Now look at the silver duct box above (or beside on a horizontal) furnace, the duct sheet metal box. Is it sweating? Does it have ice or water around it? There is the evaporator coil inside that. It will have an insulated tube going into it and a small copper tube, and a drain from it.
If there is ice, maybe sweating, it is very cold, but there is little air coming from the registers, then it is frozen up, and there is a giant ice cube inside.
SOLUTION: Shut all power down for the outdoor Condenser AC unit at the breaker if possible. Or turn the thermostat OFF. Unfortunately, it will require 24 hours or more to thaw completely. This tends to happen for several reasons, usually when it is extremely humid out. A plugged air filter is the most common cause and the easiest to fix.
After changing or removing the air filter, wait 24 to 36 hours and try it again.
If it happens again, please call us! 519-372-2978.