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Discussion Starter #1
This happened once before with the a/c and I bumped the bottom side of the dash on the passenger side and it started back working. I have has the vehicle for 2 years and it has always sounded like jet engines when first started but it winds down after a minute or so, the past few weeks it has been louder and the sound lasts longer. This morning the heat stopped blowing and the bump to the dash did not help. Also #4 setting has never worked. Any ideas or advise? Thank you!
 

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2004 gmc envoy_slt
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You may have a poor connection at the Blower Motor Control Module (might be loose, contacts corroded or connector has overheated and melted). This module is behind the glovebox. The module could also be defective.
As far as the roaring sound from the engine, this is the fan clutch causing the fan to run at full speed. This may happen because the clutch is going bad or in very cold weather, the viscous fluid in the clutch causes some resistance, but that will resolve itself with warm-up.
 

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Discussion Starter #3
You may have a poor connection at the Blower Motor Control Module (might be loose, contacts corroded or connector has overheated and melted). This module is behind the glovebox. The module could also be defective.
As far as the roaring sound from the engine, this is the fan clutch causing the fan to run at full speed. This may happen because the clutch is going bad or in very cold weather, the viscous fluid in the clutch causes some resistance, but that will resolve itself with warm-up.
Thank you. Do you know if the module is something I can replace myself? I am a female, not a mechanic, but I can do some things to vehicles and I follow directions very well.
 

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2004 gmc envoy_slt
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If the connector is overheated and melted, it will have to be replaced, that will involve soldering. Wired pig-tails are available in auto parts stores. As far as the module, it is simple to replace.
 
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