No heat when engine is at low rpm or idle.

Same problem with my 2005 Altima V6, with only 44k miles on it!!! and this is the second winter in the last 4 years that I have to pay for a coolant flush to fix the problem. This time the thermostat is getting replaced too. Time for a new car!

If engine temp. is good. i would rec. good flush of the heater core disconnect both heater hoses and flush core in both directions. (pressure washer works good)

The problem is traped air in your cooling system that wont let the heated coolant pass thru the heater core at idle it will bypass it. when you get in the gas going down the road it will go pass the air into the heater core when you let off the gas the air keeps it from passing through the core it will bypass the core and still cool engine so if no coolant going through the core no heat. the fix you can raise the front of the car on a set of car ramps remove coolant cap and try to let the air move out of the coolant this takes time. or your dealer can pull a vacum on your cooling system and remove the air . trust me this is your trouble . i hope this helps seems to be alot of people with the same trouble . remember remove the air

These cars are very sensitive to incorrect antifreeze mixtures. If you have too much coolant and not enough water the heater performance will suffer. Make sure there is a least a 50/50 coolant water ratio.