Heater controls on 2000 Chevrolet S10

Why would I not be able to get hot air from the heater when engine is at normal operating temperature?

Asked by for the 2000 Chevrolet S10
you could have a defective or malfunctioning temperature blend door. Its job is to direct the air over the heater core, so it gets warmed up!
Thanks for the response. I was thinking maybe the control in the dash. If one were to check the blend door you mentioned, where would one find it, firewall or under dash?

I know on my 2000 Silverado, the entire dash had to come out to replace my heater core!
2 more answers
Sounds like your heater core is air locked, and it just needs to be back flushed.