Ya I have a 2002 Nissan sentra,the car temp gauge goes to max heat ,,but its blowing cold air inside the car ,,,and im already in cold weather ,,got any ideas" could really use some help!!

More than likely you have a problem in the temperature control blend door and or actuator.

Sounds like the heater - ac door actuator is not working. This part would need to be replaced, it's not repairable.

Are you talking about the engine cooling system or a problem with your Auto A/C?

Looks like you have air in your coolant.

this problem is caused by a defective fual gauge sending unit inside the gas tank.

I have 2002 Nissan ser with 120k, and I noticed a different temperature change when I start my car up...it takes a while to get warm. The weather has been cold lately, but my car has quick jolt as I'm driving until the car warms up. What is this issues I'm having...?????

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.

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Paul 'W' U.K

My 2005 Nissan Sentra 1.8s with 55,000 mi. blows cold air from the heater. Coolant not circulating in engine. Lower hose stays cool to touch. Both heater hoses cold. Changed thermostat - didn't fix it. Coolant not leaking or dirty. None in oil - no oil in radiator. Changed worn water pump belt - pump spins freely with no noise or resistance. Cooling fans come on after warm-up. Temperature gauge stays in normal range then jumps to hot and back again. Coolant good to 10 below - didn't freeze here yet. No other problems or repairs to car. Afraid to drive and make worse. Help!

Sounds like you are either low on coolant, or a head gasket failure.

sonds like air in your pipes!!! run ya engine with the lid off your expansion tank and put your heater on low until water starts bubbling and may start going down in your expansion tank and if so keep topn up to max mark!!!