2001 Heater Problem

[Brownie]

After the car is warmed up and I stop at a stop light the heater starts to blow cold air. As soon as I get going again the car will blow hot. It repeats itself over and over at each light. Is this due to some sensor or thermostat located wherever? This is the first problem with the car approaching 93,000 miles.

[NSR_s30]

Sounds like a bad thermostat.

[Brownie]

Found the problem !! Air bubble in the radiator. It was probably caused by the overflow basket getting low. This is a common problem with the Sentra. They have no heater control valve. Raise the front end 18 inches off the ground and remove the radiator cap. Run the engine with the radiator cap off and the heater can be on or off. BINGO !!!! It worked !!!