Heater is not hot and the temp gauge goes hot

[Tyke]

I have a 2004 Nissan Altima, V6. The heater blows cold air and the temp gauge will go from medium to hot and go back to medium as you are driving down the highway.could this be the thermostat?

[KineKilla]

That's exactly what it sounds like.

[NutriaforBreakfast]

There is also a climate control item that controls the degree ofheating and cooling that can break.(The deal you slide towardheat or cold when you heat or ac is on)

[MinisterofDOOM]

If the needle is jumping around a lot, it may mean you have air in the coolant system. You can try and flush the air out by running the car with the radiator cap off (careful about removing the cap while too hot!) and adding fluid gradually. It can help to do this with the front of the car elevated so that the radiator opening is above the rest of the system.

[MCovington]

Typically Tstats stick open or closed, they do not usually fluctulate the water temp. It sounds like you are low on coolant.

[Nissan6Maxima]

Also check to see when the car is running and the fan comes on, check the lower radiator hose. It might take a while to warm up, if it doesnt warm up after awhile or at all. Check your thermostat. maybe