Check the heater hoses if they are both hot (one is very hot the other a little cooler) then the problem is the air temperature control HVAC blend door actuator or the blend door is sticking in the duct it sits in, in most cases the problem is with both parts. In order to repair this the entire dash must come out to access the defective parts. Please have this diagnosis/guess confirmed as this is a very expensive repair.
SOURCE: NO HEAT IN 2002 ALTIMA
you may need ot do a cooling system flush, go buy a bottle of radiator flush, put it in the radiator when it is cold, run the car for about 15 mins, and go up to the car wash and take the upper rad hose off, and use the power washer to push all of the gunk and anti-freeze through the system. do it until it runs clean.... let the car run for 2 mins with the hose off after flushing and buy straight antifreeze, not 50/50. add it to the radiator, you should have heat.....
If this does not work, then your control unit in your dash may be bad....
SOURCE: no heat
CHECK THE HEATER CORE. MORE THAN LIKELY IT IS PLUGGED OR THE HEATER CONTROL VALVE IS NOT FUNCTIONING PROPERLY. THE HEATER CONTROL VALVE CONTROLS THE WATER TO THE HEATER CORE. THUS NO FLOW, NO HEAT. GOOD LUCK.
SOURCE: no heat ,blows cold air
It is likely that the thermostat has failed and is stuck wide open as a failsafe. This jsut happened to me last week in my VW golf. Your engine will never come up to temperature but as long as the thermostat stays open it will not overheat either. Change the thermostat ASAP in case it the failsafe doesn't keep open and you overheat the engine.
SOURCE: Blowing Cold Air
It sounds like you need to do a process of elimination, by following the travel of the hot coolant.
1. Before beginning, safety must come first, so put on a pair of safety glasses/goggles and a pair of gloves.
2.Open the hood and check the coolant level, and add if needed. If you needed to add then recheck for heat after step # 3
3. Close the hood and start and run the engine to normal operating temp.
4."TURN THE ENGINE OFF"
5.Reopen the hood and lightly grasp the top radiator hose feeling for heat caused by hot coolant in the hose. Also feel the bottom radiator hose for heat, (you may have to access the bottom hose from under the car) (while down there look for coolant leak...dripping) If heat is somewhat equal between the two hoses move on. If not there are three areas to check
A) Your thermostat may not be opening
B) Your radiator might be obstructed/clogged
C) Your water pump may not be functioning
6. Locate the two smaller hoses that lead to and from your heater core (a small radiator type device located inside cab under the dash that connects through the firewall) (one is connected at the water pump to the heater core the other is connected at the engine to the heater core) one hose may have a regulator (a small mechanical device operated by either cable,electric,or vacuum that controls the flow of coolant into the heater core) attached inline
7. With the hood raised, restart the engine and adjust the heater control to max heat. Locate a safe area under the hood (free of all moving parts) to access and grasp each of the smaller heater hoses, check for heat, caused by hot coolant in the hose, also check the hose before and after the regulator described in step # 6.
If either of these locations are cold to the touch we can safely say we have narrowed the problem down to one or all of three things.
A) If all heater hoses are cold or only the inlet side of the regulator is hot and the other side is cold or warm, its possible that the regulator is faulty requiring a replacement or is not functioning due to inadequate cable,electric,and/or vacuum to operate it caused by a broken cable, electrical short or disconnected/ broken vacuum line, it also could be a defective (in dash) heater control unit or just a fuse if its electrically operated.
B) If the inlet hose to the heater core is hot and the other outlet hose is cold or warm then its possible that the heater core is obstructed/clogged, requiring a flush out or replacement.
C) If all heater hoses are hot (you may also feel a flow vibration in the hoses) then you should have heat, unless the under dash duct work is disconnected or blower fan is not operating.
I hope this helps.....
SOURCE: No heat. Fan blows cold air.
I think u may have an air temperature control blend door problem, the door is moved by a small electric motor, it is stuck in the cold position.
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