This is making me crazy! I have told everyone that works on cars I can think of, including the Chevrolete dealership, and all I get is "duh"!
I have an 02 MC LS with 84K
When I have the fan for the heater set on as high as it will go, it blows just fine as long as I am either accelerating or in motion. As soon as I either slow down to 5mph or stop, the fan power drops significantly. This "phenomenon" only occurs when the blower is on the highest setting. As far as I can tell it only happens when the rear defrost is on simulatiously and it is absolutely freezing outside. AND it goes away after the car warms up. Just an FYI, the rest of the settings for the fan work fine and when I use them for the Air Conditioner, they are fine.
Is there anyone out there that has ever experienced this, had it fixed, or fixed it on thier own?

Please advise!

 

try to replace the switch for the fan it sounds like it is worn out i had to replace the switch for my chevy silverado. i also got a duh responce from the dealer about it

 

i believe that mine does that as well...ill try it when i leave class today

 

yea mine did that too, Im sure its just the amount of power that its pulling... When u speed up, more juice is created thus giving it a boost. I ended up replacing the blower motor and resistor and it fixed it.