Okay, so today i was in the process of replacing my heater core when i discovered a possible reason my heat may not be working....

When i took out the glove box, i looked at the blower motor assembly and saw that the little sliding door thing above it was open. I could stick my hand down into the blower motor.

I thought this door was supposed to stay closed. So i went to close it and found it is broken. The door is just sittin in there loosely.

Would this door being open result in not feeling any heat through my vents? What is the name of this part and can i/where would i buy another one?

Really would like some opinions since im right in the middle of replacing a heater core that i may not even need to replace, it seems.