# F-150 Shakes When Braking, Only When A/C Is On

**URL:** <https://community.cartalk.com/t/f-150-shakes-when-braking-only-when-a-c-is-on/80547>\
**Category:** Maintenance/Repairs\
**Tags:** ford\
**Created:** [July 26, 2013, 8:02am UTC](https://community.cartalk.com/t/f-150-shakes-when-braking-only-when-a-c-is-on/80547 "2013-07-26T08:02:54Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Cargobang](https://avatars.discourse-cdn.com/v4/letter/c/6de8d8/32.png) [@Cargobang](https://community.cartalk.com/u/Cargobang)\
**Post date:** [July 26, 2013, 8:02am UTC](https://community.cartalk.com/t/f-150-shakes-when-braking-only-when-a-c-is-on/80547/1 "2013-07-26T08:02:54Z")

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I have a 1997 F-150 4.6 Liter 2WD AT  
It rides and brakes smoothly when not running the A/C  
When I switch on the A/C it still rides and runs smoothly and still brakes smoothly at first.  
After a few minutes, when I brake, the front end shakes slightly. While not braking it’s still fine.  
The problem doesn’t go away immediately when I switch of the A/C, but does eventually.  
However, on rare occasion the front end will start shaking like I have a square tire, even when not braking.  
This never occurs when I’m not running the A/C  
Pads and rotors seem fine, tires are good, on visual inspection.  
A/C blows cold and the clutch seems to engage/disengage properly  
Any suggestions?

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**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\
**Post date:** [July 26, 2013, 8:14am UTC](https://community.cartalk.com/t/f-150-shakes-when-braking-only-when-a-c-is-on/80547/2 "2013-07-26T08:14:55Z")

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The next time this happens with the engine idling, open the hood and with the handle of a scewdriver rap on the idle Air Control valve. If the engine idle speed changes replace the IAC valve.

Tester

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<div class="post-metadata">

**Author:** ![Cargobang](https://avatars.discourse-cdn.com/v4/letter/c/6de8d8/32.png) [@Cargobang](https://community.cartalk.com/u/Cargobang)\
**Post date:** [July 27, 2013, 12:31am UTC](https://community.cartalk.com/t/f-150-shakes-when-braking-only-when-a-c-is-on/80547/3 "2013-07-27T00:31:12Z")

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Thanks for the input, I’ll give that a shot

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<div class="post-metadata">

**Author:** ![Cargobang](https://avatars.discourse-cdn.com/v4/letter/c/6de8d8/32.png) [@Cargobang](https://community.cartalk.com/u/Cargobang)\
**Post date:** [August 2, 2013, 11:16pm UTC](https://community.cartalk.com/t/f-150-shakes-when-braking-only-when-a-c-is-on/80547/4 "2013-08-02T23:16:25Z")

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Tester, It very rarely does the constant shake, but I tried what you said after running the A/C  
to get the “Brake Shake”, there was no change in idle speed.  
Do you think it needs to be in the constant shake mode for this test?

Any other ideas?