One problem related to defogger has been reported for the 2004 Chevrolet Impala. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2004 Chevrolet Impala based on all problems reported for the 2004 Impala.
Hvac system in the 2004 Impala has a problem. The ac compreser runs in the heat only mode at temps as low as 30 degrees. This causes the inside windows to fog up on the inside and if the vech is left parked outside all the windows will fog up. The only way to keep all windows clean is to open one of the windows a little and run defrost with at least half speed. If you do not do this the front and side windows fog up and it is very hard to cleat the side windows. This problem is causing my gas mileage to go down and making it hard to drive when it is cold out. Dealer said it is ok. The manual says the ac sould only run above 40 and only in defrost or demist modes.