# Engine stalls when A/c is on **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** fiesta, ford\ **Created:** [February 24, 2020, 11:58am UTC](https://community.cartalk.com/t/engine-stalls-when-a-c-is-on/159395 "2020-02-24T11:58:29Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![Harichand](https://avatars.discourse-cdn.com/v4/letter/h/ba8739/32.png) [@Harichand](https://community.cartalk.com/u/Harichand)\ **Post date:** [February 24, 2020, 11:58am UTC](https://community.cartalk.com/t/engine-stalls-when-a-c-is-on/159395/1 "2020-02-24T11:58:29Z")
I have a 2007 ford fiesta classic (petrol) manual transmission. The car stalls when A/c is on mainly when slowing dow or down shifting from 4-3 or 2-1 ,the rpm drops or i don’t know why. and some time when A/c is on the engine starts vibrating very roughly ,when i turn off the engine and the turn it back on it goes back to normal. All these problems happen only when A/c is on. Please help ---
**Author:** ![Rod-Knox](https://avatars.discourse-cdn.com/v4/letter/r/a183cd/32.png) [@Rod-Knox](https://community.cartalk.com/u/Rod-Knox)\ **Post date:** [February 24, 2020, 1:51pm UTC](https://community.cartalk.com/t/engine-stalls-when-a-c-is-on/159395/2 "2020-02-24T13:51:47Z")
A likely cause is carbon buildup on the throttle bore which isn’t difficult to clean. There are products made somewhat specifically for that purpose. ---
**Author:** ![tcmichnorth](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tcmichnorth/32/25126_2.png) [@tcmichnorth](https://community.cartalk.com/u/tcmichnorth)\ **Post date:** [February 24, 2020, 2:17pm UTC](https://community.cartalk.com/t/engine-stalls-when-a-c-is-on/159395/3 "2020-02-24T14:17:01Z")
A less likely cause would be a fault in the system that is supposed to trigger the rpm to rise at idle when AC is on. Another less likely cause would be a failing compressor. And another could be a faulty compressor switch.