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Air condition

My air conditoner blows cold air until I accelerate quickly (as in passing another car)then it blows warm air until I resume my normal speed. What is the reason/cause for this.

Engine vacuum holds airflow control doors called “blend doors” in certain positions. When you accelerate, you lose engine vacuum and the door changes position. Most cars have a “vacuum reservoir”, a can mounted somewhere, sometimes inside a fender, which is supposed to maintain vacuum on the heater controls and thus avoid the problem you have. You could have a shop check for vacuum leaks in the heater control system…