Why is my 2001 Chevy Blazer heater blowing cold air?

[CoryH]

For the past few days, my truck's heater has been blowing cold air. I check the engine coolant and it was low (really low). I added coolant but the heater is still blowing cold air. How do I tell if it is a bad heater core or a thermostat?

[SteveO]

If the thermostat gets stuck open the car will run cold. I think that is the case with your vehicle. Let it warm up a while and check the temp guage. If the temp is below 190 it is the thermostat. If not post the new info and we can go from there.

[photou2]

Unless the heater core is completely stopped up it will blow a little warm, it may very well be your thermostat.Do a simple Replacement of the thermostat. not that expensive, and even if its not the problem it all comes with summer and weatherization of your vehicle. also befo you change the thermostat feel your heater hoses to see if they are at least warm if they are hot it may be your heater core.good luck wit this.

[SteveO]

If the thermostat gets stuck open the car will run cold. I think that is the case with your vehicle. Let it warm up a while and check the temp guage. If the temp is below 190 it is the thermostat. If not post the new info and we can go from there.