Blows cold air
Have 2002 altima,blower works no heat at idle and very little heat when accelerating.I changed carbon cabin filter,made sure little gear under dash to temp knob wasnt broken,flushed and bled system.Nothing worked so checked hoses to heater core and found inlet hose was hot,outlet hose was not.So investigated this problem and came to conclusion heater core was clogged.An easy way to check is to get car to normal running temp. put on heater and blowers at full.Go under dash on passenger side where counsel meets firewall,this is where heater core core inlet and outlet aluminum tubbing go through firewall,you will be able to feel both tubes one closest to you is outlet, so if this one is not hot and and other is your heater core is clogged.I detached both inlet and outlet hoses to heater core from water control valve.Then I blasted water with waterhose and nozzle set at jet,first through outlet hose to blow gunk out,then through inlet hose until water runs clear.Reatach hoses fill and bled system.heater works great nice and hot!
have 2002 altima,blower works no heat at idle and very little heat when accelerating.I changed carbon cabin filter,made sure little gear under dash to temp knob wasnt broken,flushed and bled system.Nothing worked so checked hoses to heater core and found inlet hose was hot,outlet hose was not.So investigated this problem and came to conclusion heater core was clogged.An easy way to check is to get car to normal running temp. put on heater and blowers at full.Go under dash on passenger side where counsel meets firewall,this is where heater core core inlet and outlet aluminum tubbing go through firewall,you will be able to feel both tubes one closest to you is outlet, so if this one is not hot and and other is your heater core is clogged.I detached both inlet and outlet hoses to heater core from water control valve.Then I blasted water with waterhose and nozzle set at jet,first through outlet hose to blow gunk out,then through inlet hose until water runs clear.Reatach hoses fill and bled system.heater works great nice and hot!
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SOURCE: 2002 Nissan Altima blowing cold air,coolant level
You could possibly have air trapped in the heater core. The easiest way to bleed it out is to jack up the front of the car till the radiator fill cap is higher than the upper heater hose using a funnel that fits snuggly in the filler neck of the radiator, fill till you have about three inches of coolant/antifreeze above the filler neckthen run the car at about 1500rpms until no more bubbles are evident. Also turn the heater onto face on low speed and feel if heat starts comming out.
SOURCE: heater blows cold air at low speed and idle
I worked at a Nissan dealer for 18 months and we'd get a lot of these in. The cold heat at idle is accompanied by a sloshing noise from behind the dash - you've got an air pocket in the heater core. What we used to do was lift the front end of the car about 3 feet off the ground using the hoist and take the rad cap off. Then we'd run the engine at a fast idle (jam a screwdiver against the throttle stop to hold it fast or put a slight weight on the pedal if it's Electronic Throttle Body. Run the heater on full heat and the engine like this. You'll see the rad 'burping' as the air in the cooling system travelling to the highest point it can - the open rad cap. Top up with a 50/50 mix of coolant and water as you go. When it burps no more, you have a full cooling system and should not suffer any more "cold heat".
If you do this yourself, PLEASE use jack stands, block the back wheels and put the parking brake on!!!
answer from a Nissan mechanic, (not me)
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.
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