# A/C stops blowing and makes whistling noise on highway?

**URL:** <https://community.cartalk.com/t/a-c-stops-blowing-and-makes-whistling-noise-on-highway/79508>\
**Category:** Maintenance/Repairs\
**Tags:** chevrolet, aveo\
**Created:** [May 24, 2013, 11:55pm UTC](https://community.cartalk.com/t/a-c-stops-blowing-and-makes-whistling-noise-on-highway/79508 "2013-05-24T23:55:14Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![bhraki](https://avatars.discourse-cdn.com/v4/letter/b/8edcca/32.png) [@bhraki](https://community.cartalk.com/u/bhraki)\
**Post date:** [May 24, 2013, 11:55pm UTC](https://community.cartalk.com/t/a-c-stops-blowing-and-makes-whistling-noise-on-highway/79508/1 "2013-05-24T23:55:14Z")

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I am having trouble with my Chevrolet Aveo 2009 A/C. After driving for a while on the highway, the A/C stops blowing much air at low fan and when I increase the fan speed, it blows more air while making a whistling noise but not as much air as it usually does on that same fan speed. The noise starts going away after a while and it blows as much air as it should.  
I noticed that it happens more when I keep accelerating every now and then on the highway. It does not happen as much when I am driving on a constant speed. I took it to the dealership and they said the filter was dirty and they found a leak on the vaporizer cap, fixed those but nothing changed!  
Has anyone experienced a similar issue with their A/C? What might be the cause? I was researching the issue and came across this "“TPS (throttle position sensor) gives the WOT (wide open throttle) signal to the PCM to momentarily cut off power to the A/C clutch which disengages the A/C”…Could that be the issue?

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**Author:** ![DanielLee](https://avatars.discourse-cdn.com/v4/letter/d/7feea3/32.png) [@DanielLee](https://community.cartalk.com/u/DanielLee)\
**Post date:** [May 25, 2013, 5:04pm UTC](https://community.cartalk.com/t/a-c-stops-blowing-and-makes-whistling-noise-on-highway/79508/2 "2013-05-25T17:04:05Z")

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your ac evaporator may be freezing up. there is either a pressure switch or a temperature sensor that shuts off the compressor before the evaporator reaches 32\*F, so the condensation water won’t build up and block air flow. or the compressor relay may be sticking on. most likely, cheapest and easiest is the relay. i don’t know what a “vaporizer cap” is.