When in cooling the system blows air normally. When in heat it is unable to blow a significant amount of air through. You. Can hear the blower revving up trying to push the air through, it appears there is a door not opening to allow it to be adequately forced through the heater core. At one time someone was able to move something from the passenger side and it blew normal, but for the life of me I don't know what that was.
Blowing very little hot air on 2001 Pontiac Grand Prix
by Radrich in Monroe, MI on August 11, 2014