My car wasn’t heating well, even though I had a new thermostat put in. So I had the the thermostat changed out and topped off the anti-freeze. But still I’m only getting slightly warm air, and it’s in the teens! I have a new radiator & hoses in the car; heater core is old. What gives?

Heater core is probably partially plugged. You might be able to flush it somehow but I had to replace mine.

Thanks, I’ll check with my local radiator shop.

Heater core may be plugged or you may have been low on coolant. The fact that they topped off the coolant indicates that it may have been low and if low that would have increased the possibility that there is an air bubble in the system and that could be the problem. The shop may need to burp it. Not a big thing.

There is also the possibility that there is a control issue but the shop should check for that as well.

Good Luck

yet another possiblity is the blend air door. If it’s jammed, it’s letting cold air in to mix with the hot air, resulting in luke warm air. Have that checked as well.