Heater blows cold air

SOURCE: Heater blows cold air when idle

Sounds like you may have a partially plugged heater core. You could flush this out separately, from flushing radiator & engine block. Diconnect heater hoses going to your heater core and clamp off, so not to loose coolant from engine. Now hook up separate hose to one side of heater core pipe and flush out with typical garden hose. Repeat procedure on both heater core inlets. Reconnect original heater hoses and test difference. You may have to add an additional litre of antifreeze. If this don't work i suggest changing heater core. Good luck.........Ron.

SOURCE: Heater blowing cold on 2005 Nissan Xterra

I live in Alaska and have had the same problem i just added more coolent to the radiator and it warmed up i installed a block heater and i leaked a bit and the coolent level got low and i would have no heat. I tryed to fill just the coolent resivoir and that dident work so i filled the radiator pumb full and that worked!! Hope this helps.

SOURCE: Heater on driver-side blows barely warm air other vents blow cold

the most probabale cause of this would be a disfunctional hear core if you replace your heater your heater will more than likley work the the way it's supposed to

SOURCE: Heater blows cold air unless accelerating

See my posted question under 2001 Mercury Villager: "HEAT BLOWS COLD WHEN CAR IS IDLING" I got an answer from chuck943 about air pockets and it was very helpful.

SOURCE: blowing cold air

I had the same problem that I just fix by flushing the heater core out with a hose.   take the two hoses off the fire wall and put the water to it and let flush.  my heater is putting out 150 dg. F  of hot air.   I'm so excited!  i will stay warm now.