No heat

My girlfriends 95 grand am suddenly lost its heat. The car is full of coolant and has no heating issues. The blower fans work great too. I wouldn’t think the heater core would all of a sudden get plugged up. I was wondering if there’s a valve of some sort that allows the coolant to enter the here core, maybe that’s stuck closed. And if so, where is it located. I really hope it's not the heater core because i know they're a PITA to get at. Anyone know the book time on a heater core?

Any advise would be great. It’s starting to get cold up here. Thanks.

Took me 5 hours to change my heater core. And I had to deal with mosquitos. Easiest test for it is to disconnect the heater hoses, attach a garden hose to one end and let it fly. If you get strong flow through the heate core, then check the temperature control cable. If that's good, you might have a mouse that has taken up residence on the heater core. That's just as much fun as changing the heater core itself, except you don't have to disconnect the hoses.

Did you have a chance to watch thermometer on the instrument board when you had no heat? If the coolant temp does not reach near 200 F, you may get some heat at the highest setting. The thermostat may be bad if you still have low coolant temp after you drive the car more than 10 min.

Well after farting around with it for 5 minutes, the heat control knob fell off. The inside of the keyway was cracked so it wasn't gripping the key. The key was on the "cold" position, so I used and adjustable wrench and turned it to "hot". She’s pumping hot air now.

Off to the junk yard for a new knob. Glad it was something simple. Thanks guys.

When searching for knobs try to find them from a 96-98, they are of a more durable construction and less likely to break. I went through a bunch that I had bought new for my 95, then stumbled across a 96 when looking for a radiator.