# Air condition

**URL:** <https://community.cartalk.com/t/air-condition/33776>\
**Category:** Maintenance/Repairs\
**Tags:** nissan, 300zx\
**Created:** [July 22, 2009, 12:02am UTC](https://community.cartalk.com/t/air-condition/33776 "2009-07-22T00:02:48Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![csb322](https://avatars.discourse-cdn.com/v4/letter/c/2bfe46/32.png) [@csb322](https://community.cartalk.com/u/csb322)\
**Post date:** [July 22, 2009, 12:02am UTC](https://community.cartalk.com/t/air-condition/33776/1 "2009-07-22T00:02:48Z")

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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.

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**Author:** ![Caddyman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/caddyman/32/23_2.png) [@Caddyman](https://community.cartalk.com/u/Caddyman)\
**Post date:** [July 22, 2009, 12:44am UTC](https://community.cartalk.com/t/air-condition/33776/2 "2009-07-22T00:44:42Z")

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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…