2006 impala lt defroster does not blow sfficient air to clear window. heater works in all positions except window defrost. The fan appears to be blowing hard but air not reaching the window. Just happened today in -30 celcius temp. Vehicle thawed out but still would not work. Any suggestions as to repair and how difficult to repair.

SOURCE: 2006 Chevy Impala Heater only works when accelorater is depressed

Impalas are known for this issue, where the heating won't work properly.... usually caused by trapped air/bubbles in cooling system or slightly low coolant level. Park car so that the right front side is elevated and remove the coolant OVERFLOW bottle cap (NEVER the radiator cap) while engine is running.. This should allow the trapped air to escape. Also add a bit more coolant if needed.

SOURCE: 1996 chevy blazer my air on heater will not blow

the idea of the switch is run on vacuum and is not making contact with the switch it self either worn contacts in the switch itself **** as an obstruction as well or the vent door is stuck in just that position either behind the glove box or the ash tray are the vacuum lines one of them may be pinched off or the door needs a bit of help until you can free it up

SOURCE: 2004 Chevy Impala no heat from defrost or heater

No heat is often a symptom of low coolant, usually followed by overheat. There are other controls that regulate heater, but right now, re-fill the cooling system with engine running and heater on high, then check for leaks (coolant you lost went somewhere...you need to determine where) Low coolant will damage your engine. Take care of that first, then if heater still does not work, then do diagnosis on that. (if you loose the engine heat won't matter, will it!)

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SOURCE: 2005 impala. Rear window defroster is not working

they have a fuse and a rely make sure the wire end is on the conector on the window

SOURCE: where is relay and fuse for rear window defrost

Where is relay and fuse for rear window defrost