Heat problems.. I had the heating system flushed(as per the service tech in the nissan dealer), the heat worked a little but now it only blows out cold air; to add to the problem, the temperature control knob on stays on the side for heat and does not turn to the (blue) cold side. What is the best suggestion on what to do, I hate to have to dish out $$$ at the nissan dealer only for them not to solve the problem again.

The lack of heat in the car has little to do with the car's cooling system, other than the hot coolant is the heat source. 95% of all "no-heat" issues are related to heater controls and/or the heater core itself. Since you get some heat, and then it goes away, this indicates a probable vacuum leak in the heater controls. When you select heat, vacuum is directed to a vacuum motor. This motor operates a vacuum actuator that moves a linkage that moves a door inside the heater box to direct the interior air through the heater core. If this actuator has a leak, it will activate, then as the vacuum leaks off, deactivate. You probably need to have a part replaced in the heater actuator mechanism.

fan blows?
engine reaches and holds 180F or more , normal engine temp?
(use a IR pyro gun to measure it)
ever go a cooling system flush, if not the heater core could be packed full of junk.
id the dampers fail , its not in heat mode.
check the dampers after checking engine heat.

it only takes 2 things to make any water to air heat exchanger to work.
hot water
and actual air flow.

check for hot water first (engine coolant)

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!

If the engine has overheated, chances are pretty good that you now have a warped or cracked cylinder head and a blown head gasket. Those engines are very unforgiving when it comes to being overheated.

yes,have suggestion.leaking coolant into the passeger side floorboard? film on the windsheild at anytime? suggest a bad heater core. or this,heater core stopped up.needs to be flushed.flush radiator with a common flush found at autozone,advance autoparts stores.or any other auto parts stores. remove your heater core hoses on the firewall[2 small hoses that go from the motor through the firewall to the heater core itself] flush the heater core there manually.push your water hose to the passenger side there and turn hose 'on' and watch the flow out the other side.[both hoses on the firewall will have to be off[or disconnected]to do this properly. your problems here,and since you've replaced the thermostats twice,suggest that this is your issue. thank you for choosing fixya.com

Welcome to FIxYa.com

This is a classic symptom of low coolant level or air in the system. Too, clogged heater core.

Buy a 5 min flush from your local dealer. With a gallon of Anti freeze and water pump lube. Flush the system per instructions on the back of the 5 min flush bottle. And add the one gallon of anti-freeze to system. The top off with water. Make sure engine is running with the heat selector on and fan on high.

See if the will work if not Change thermostat.

Thank you for using FixYa.com

Regards, Lee Davidian

One or more of:

1. Your coolant is low
2. Your thermostat doesn't close and needs to be replaced
3. The valve from the cooling system to the heater core is stuck
4. Your heater core is clogged

Trash build up gets caught in the heater core usually because coolant flush isnt done oncea year. What needs to be done is disconnet heater hoses and blow heatercore out with shop air.

take to dealership , that also is a recall problem with alot of altimas , they need to flush system and check water valve , got mine fixed working great ever since , never hesitate to ask dealership about recalls , they have to fix for free

next time you go up a hill see if the heat is still blowing