Heating issue. 1994 Nissan altima, when parked or at a stop light the heater blows cold air during the winter. I will heat up if moving, any suggestions

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.

your heater core is possibly stopped up if there has been a radiator leak and stop leak has been poured its definetly clogged or could be a faulty thermostat

Is the vehicle fitted with climate control?If so, then check the function of the cabin air temperature sensor and check that it is also clean.

On the a/c send the radiator to flush,as for the heater you need to check the vacuum hoses that goes into the contrl panel,check for a leak on vacuum in the engine as well.

you may have a sticking thermostat make sure you have enough anti-freeze in it and it does not have a air bubble in it give these websites a try www.alldatadiy.com and www.autozone.com if all fails stop by your local library and get your hands on a Haynes auto repair manual for your car wish you the best of luck Michigan Man.

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)

Check coolant level, make sure it's at the proper fill mark when cold.
Partially blocked heater core - back flush cooling system
Defective heat control valve.
Hope this helps.

Hi!
It appears we have an Air lock scenario and you will need to perform a system Bleed.
Park the vehicle on level ground, when cold remove coolant filler cap, start engine and leave to idle, turn heater on full and blower to max. When engine reaches operating temperature watch and listen near coolant filler, keep clear as gurgling and hopefully a boil over should occur. Top up with very warm coolant and wait as it may do it again.
Check for heat inside vehicle if warm replace coolant cap but keep an eye on temperature gauge as the ~Air lock may have moved on from heater matrix/core so proceedure needs to be carried out again from COLD.

Please press the Blue button to appraise my FREE Efforts, Thank You!
Paul 'W' U.K

Hya!
You need to bleed the cooling system.
To do this park on level ground, when cold remove coolant filler cap, start engine and leave to idle.
Have plenty of warm/hot water available, when engine reaches operating temp it may appear to boil over so keep away from coolant filler, top up with warm/hot water and wait as it may bubble over a few times before settling.
Replace cap and hopefully back to normal, Remember your Anti Freeze?
Good luck,
Paul 'W'
Oner~EDson(:0) {#><U.K.

you can take a little time but you should definitely replace it soon if you have cold weather where you live.

Engines need to be warmed up by the coolant in the winter time.