# A/c stops working going uphill

**URL:** <https://community.cartalk.com/t/a-c-stops-working-going-uphill/54442>\
**Category:** Maintenance/Repairs\
**Tags:** airconditioning, windstar, ford\
**Created:** [August 31, 2010, 4:19am UTC](https://community.cartalk.com/t/a-c-stops-working-going-uphill/54442 "2010-08-31T04:19:30Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![vijay\_a](https://avatars.discourse-cdn.com/v4/letter/v/e5b9ba/32.png) [@vijay\_a](https://community.cartalk.com/u/vijay_a)\
**Post date:** [August 31, 2010, 4:19am UTC](https://community.cartalk.com/t/a-c-stops-working-going-uphill/54442/1 "2010-08-31T04:19:30Z")

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A/c stops working when I am going uphill even if it a very slight uphill. No air comes from vents.

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**Author:** ![BustedKnuckles](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/bustedknuckles/32/25_2.png) [@BustedKnuckles](https://community.cartalk.com/u/BustedKnuckles)\
**Post date:** [August 31, 2010, 9:29am UTC](https://community.cartalk.com/t/a-c-stops-working-going-uphill/54442/2 "2010-08-31T09:29:13Z")

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You have a bad vacuum check valve. The check valve is there to make sure the vacuum to the vents is maintained when the engine vacuum drops, like when you accelerate up a hill.

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**Author:** ![tardis](https://avatars.discourse-cdn.com/v4/letter/t/f0a364/32.png) [@tardis](https://community.cartalk.com/u/tardis)\
**Post date:** [August 31, 2010, 1:00pm UTC](https://community.cartalk.com/t/a-c-stops-working-going-uphill/54442/3 "2010-08-31T13:00:34Z")

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Bad vacuum check valve or a small vacuum leak somewhere in the climate control system. If you check, you’ll find that the missing air is coming out of the defrost outlets when this happens.

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**Author:** ![Manolito](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/manolito/32/3070_2.png) [@Manolito](https://community.cartalk.com/u/Manolito)\
**Post date:** [August 31, 2010, 1:17pm UTC](https://community.cartalk.com/t/a-c-stops-working-going-uphill/54442/4 "2010-08-31T13:17:28Z")

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On the 20-year-old car I recently sold, I would loose defrost air when driving uphill.

The check valve on that car was easy to spot - right on top of the intake manifold. Washing it with hot dish water every 6-8 years put it right.

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**Author:** ![realbinky](https://avatars.discourse-cdn.com/v4/letter/r/a87d85/32.png) [@realbinky](https://community.cartalk.com/u/realbinky)\
**Post date:** [August 31, 2010, 3:00pm UTC](https://community.cartalk.com/t/a-c-stops-working-going-uphill/54442/5 "2010-08-31T15:00:37Z")

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Right you are. I bought a used Olds Silhouette. The previous owners explained the A/C didn’t work, even though they had it charged like 6 times. I said, oh, it’s vacuum leak, I can fix that. They were stunned, I think a little upset the otherwise fine van still had A/C and no mechanic (probably dealer) helped them. And sure enough, and $11 part fixed it (was a leaking vacuum “master” switch - the selector was mechanical