# Help!

**URL:** <https://community.cartalk.com/t/help/38314>\
**Category:** Maintenance/Repairs\
**Tags:** ram, noises, dodge\
**Created:** [October 19, 2009, 3:01pm UTC](https://community.cartalk.com/t/help/38314 "2009-10-19T15:01:26Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![shane\_corter](https://avatars.discourse-cdn.com/v4/letter/s/96bed5/32.png) [@shane\_corter](https://community.cartalk.com/u/shane_corter)\
**Post date:** [October 19, 2009, 3:01pm UTC](https://community.cartalk.com/t/help/38314/1 "2009-10-19T15:01:26Z")

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after a cold night,when i go out and start the truck and turn on the heater/ac,there is a loud knocking noise on the inside passenger side from behind the dash.after a while of driving the noise will eventually go away,like arouund 30 mins,but does not happen if i turn off the heater/ac please help its very annoying

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**Author:** ![VDCdriver](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/vdcdriver/32/30_2.png) [@VDCdriver](https://community.cartalk.com/u/VDCdriver)\
**Post date:** [October 19, 2009, 3:19pm UTC](https://community.cartalk.com/t/help/38314/2 "2009-10-19T15:19:23Z")

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You have a “blend door” in the HVAC system that is hanging up and not opening properly.  
As a result, the servo motor is repeatedly trying to open it–hence the noise.

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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:** [October 19, 2009, 4:30pm UTC](https://community.cartalk.com/t/help/38314/3 "2009-10-19T16:30:21Z")

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Does the rate of knocking change with blower speed?

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**Author:** ![shane\_corter](https://avatars.discourse-cdn.com/v4/letter/s/96bed5/32.png) [@shane\_corter](https://community.cartalk.com/u/shane_corter)\
**Post date:** [November 1, 2009, 3:22pm UTC](https://community.cartalk.com/t/help/38314/4 "2009-11-01T15:22:36Z")

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yes if i turn the blower to high it speed up and down to low it will be almost like someone knocking on the door

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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:** [November 1, 2009, 3:32pm UTC](https://community.cartalk.com/t/help/38314/5 "2009-11-01T15:32:37Z")

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Remove the blower motor/fan wheel to see if the plasic fan wheel is coming apart.

Tester

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**Author:** ![Caddyman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/caddyman/32/23_2.png) [@Caddyman](https://community.cartalk.com/u/Caddyman)\
**Post date:** [November 1, 2009, 3:34pm UTC](https://community.cartalk.com/t/help/38314/6 "2009-11-01T15:34:49Z")

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Remove your glove box and you should be able to SEE the problem…Perhaps your heater box is full of acorns and the blower is tossing them around. After a while, if moves them out of the way…Perhaps the sleeping rodents themselves are seeking exit points…