There is a loud thupping noise & vibration from under dash near ventilation sys what is it & how to repair

SOURCE: loud noise from under the dash, ac/heater area. No cool air 97 li

If this noise is a clicking sound and is coming from the front center of the dash, then it may be the blender door motor which will require removal of the dash to replace it. It will keep the door from switching from heat to a/c. Does the odor smell like you have a freon leak in your a/c evaporator core or does it smell like a rat stuck in your heater and a/c ducts?

SOURCE: Loud Noise & Vibration

Who knows without inspecting it, but check the tires. Tires can cause serious problems even if they look ok. Though tires look fine, they can have an almost invisible way of vibrating a vehicle also un balanced tires can cause vibrations

SOURCE: Vibration noise from cabin ventilation fan

Pull the fan motor and look for debris. Sounds like a balance issue. Test the unit on a bench. If cleaning will not resolve, replace the unit.

SOURCE: 2006 ford fusion 34000 miles. Has loud

hi iv had a simular noise on a fusion i done and it was the water pump bearings making the noise the only way to solve this is to replace the pump ,

SOURCE: 2005 ford focus 114000 miles

Hi,

High-pitched sound is usually a belt - unlike nearly everything else, rubber expands when cold and shrinks when warm, so after start, noise goes away.
Open hood, have someone else start, and you look/listen for noise to pinpoint.
Could be just an adjustment.

Please check the bellow link:-

http://www.ehow.com/list_7223257_causes-vibration-cold-truck-engine_.html

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