blower motor

[RRROBB]

on the back side of the a/c blower motor there is a rubber tube that connects to the heater box. What is the reason for this tube? Is it necessary for a/c (I live in Texas) and heat or heat only? Any problem if I plug the hole in blower and heater box?
By the way, this is a 77 with a 94 blower retrofit.
Thanks!!!!

 

[JohnZ]

The rubber tube allows cold air from inside the evaporator case to blow into the blower motor to cool it and keep it from frying during extended "high blower" operation. Leave it there unless you want to replace the blower motor (not fun).