# A/c blows weak at high speeds

**URL:** <https://community.cartalk.com/t/a-c-blows-weak-at-high-speeds/87587>\
**Category:** Maintenance/Repairs\
**Tags:** blower-motors\
**Created:** [October 10, 2014, 2:35am UTC](https://community.cartalk.com/t/a-c-blows-weak-at-high-speeds/87587 "2014-10-10T02:35:26Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![4n6dave](https://avatars.discourse-cdn.com/v4/letter/4/e99b99/32.png) [@4n6dave](https://community.cartalk.com/u/4n6dave)\
**Post date:** [October 10, 2014, 2:35am UTC](https://community.cartalk.com/t/a-c-blows-weak-at-high-speeds/87587/1 "2014-10-10T02:35:26Z")

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Here is a weird issue on a 07 Nissan Altima. Just recently, the air conditioning started blowing weak when I hit highway speeds (around 60+). It still blows cold…, but is very faint no matter what speed the blower is on. I can still hear the blower cranking away, but very little air coming out of the vents. If i turn the a/c button off…it takes a little bit, like 20 seconds, but the air starts blowing through the vents again. Wait a bit and hit the a/c button and blammo - a/c. It lasts for about 10 minutes and happens all over again. Only at high speeds. at low speeds, everything works like a champ.

Thoughts? I have a hunch…but would like some feedback before I start tinkering.  
Thanks!

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**Author:** ![Triedaq](https://avatars.discourse-cdn.com/v4/letter/t/65b543/32.png) [@Triedaq](https://community.cartalk.com/u/Triedaq)\
**Post date:** [October 10, 2014, 6:22am UTC](https://community.cartalk.com/t/a-c-blows-weak-at-high-speeds/87587/2 "2014-10-10T06:22:50Z")

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One possibility is that the evaporator coil is icing up.

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**Author:** ![insightful](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/insightful/32/2732_2.png) [@insightful](https://community.cartalk.com/u/insightful)\
**Post date:** [October 10, 2014, 7:12am UTC](https://community.cartalk.com/t/a-c-blows-weak-at-high-speeds/87587/3 "2014-10-10T07:12:26Z")

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Yep, and it might be the evaporator thermistor and thermal control amp:

[![](http://www.stac-consulting.com/serrano.j/altima/cooling_unit.jpg) ](http://www.stac-consulting.com/serrano.j/altima/cooling_unit.jpg)

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**Author:** ![ok4450](https://avatars.discourse-cdn.com/v4/letter/o/e9bcb4/32.png) [@ok4450](https://community.cartalk.com/u/ok4450)\
**Post date:** [October 10, 2014, 8:03am UTC](https://community.cartalk.com/t/a-c-blows-weak-at-high-speeds/87587/4 "2014-10-10T08:03:40Z")

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Have you stuck a hand up on top of the dash and verified whether or not the bulk of the air is coming out of the DEF vents rather than the panel vents when it does this?

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**Author:** ![4n6dave](https://avatars.discourse-cdn.com/v4/letter/4/e99b99/32.png) [@4n6dave](https://community.cartalk.com/u/4n6dave)\
**Post date:** [October 11, 2014, 6:40pm UTC](https://community.cartalk.com/t/a-c-blows-weak-at-high-speeds/87587/5 "2014-10-11T18:40:53Z")

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I have not tried to see if the air is blowing out of the def vents but the parking pass I have up there isn’t blowing around.

Thermistor sounds compelling. I’ll keep y’all posted

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**Author:** ![knfenimore](https://avatars.discourse-cdn.com/v4/letter/k/9fc348/32.png) [@knfenimore](https://community.cartalk.com/u/knfenimore)\
**Post date:** [October 11, 2014, 8:14pm UTC](https://community.cartalk.com/t/a-c-blows-weak-at-high-speeds/87587/6 "2014-10-11T20:14:39Z")

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I would check to see if it’s coming out the defrost or floor. Does this car have the Automatic climate control?