This morning after running the car for 2 miles, my car was still blowing freezing cold air. I messed with the temp knob moving it all the way cold to all the way hot a few times. Then I started to get warm air. It happend again tonight. This time I had to turn off the car and turn it back on again. What could be going wrong? Where do I start?
This is on a '98 Chevy Malibu.
Find the location of your heater valve, and see what the temperatures are like on both sides. Might just need a new heater valve, which allows coolant to flow to heater.
2 miles isn't enough for some cars to heat up, is this the first time this has happened?
First, check your coolant level, cold and hot. If it's good, You likely need a new thermostat, the piece that controls the flow of coolant to the radiator. If that doesn't fix it, then check the heater valve as FossilizedCarlos mentioned.
I've got a mitsubishi, so it's a different car, but there is a motor that opens and closes the heater door. It's going out, so sometimes I can hear it click and either engage/disengage when I turn the heat dial, so it's an erratic problem. Could be something similar on your car.
Right now it's not engaging, so it's blowing cold air, even though the heater itself is working fine.
Turns out I was just low on coolant. Once I filled the tank it was fine again.