MY Nissan Altima has no heat in park or when stopped allthough while traviling down the road it blows warm air

If your engine temp reads warm then your heater core is clogged. Try flushing the system. If it reads cold then u need a new thermostat

Heater core may be clogged. Try flushing it to see if water flows through freely. Also check the heater water control valve for restrictions.

make sure you have plenty fluid in the radiator and the bottle. sounds like it is low.

thermostat might be stuck open need to replace it ..just went through that with my car

1st thing I would do is have your thermostat checked at a rebutable rad shop also somtimes the rad cores get blocked and will not circulate the heat properly either problem can be rectified at the rad shop...good luck

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

did you mount the thermostat properly... sounds like it is reversed

here is a picture of the proper orientation

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.

have you chg. any thing lately like thermostate? added any coolent to system? if not, thermostate could be stuck in the open position. if stuck open, setting still, it will throw heat, but moving coolent flows to fast and does not get a chance to get hot. if you did chg. thermostate it could have a air pocket in the system. and also adding coolent can create an air pockets too. you will know this when your traveling down the road and temp guage fluctuates up and down. witch means air in system.