Alright. So i'm having this issue with my altima, and it's been at the dealership for it's third time and they have to clue what's going on. Here's what's happening. First, let me say it's like 20 below where I live in Canada. When I start the car in the morning to let it warm up, the heat works great, I get in after like 5 min and heat is starting to come out. Now lets say I drive about a 1 km to a coffee shop, and leave my car on while I run inside. Looking at my temp gauge, it's at normal operating temperature and the heat is coming out at full force. After a few minutes, I get back in my car, and it's blowing freezing air, and it take a few minutes of driving to get it back hot. The temp gauge stays at the same place the whole time, being the middle of the gauge. First, Nissan said it must have had an air pocket, so they checked that and said yes that was the problem. It did it again after a day. So I brought it back and now they said the coolant was testing much to low for the thermostat the car has, so they drained some and put the correct amount to make it 50/50. Now its doing it again and they dont know what it is. Can anyone help me please. Thanks!!