2005 Chevy Impala

Electrical problem
2005 Chevy Impala 6 cyl Automatic 66759 miles

My Car has been having some trouble with the dash board. I took it to the dealership and they told me nothing was wrong.

First problem is: The gas tank when you turn the care off the gas gauge is suppose to go down to empty. It doesn't it stays at full. Then whe you turn the car over it makes the gas gauge go past the full almost all the way around in a complete circle.

Secon problem is: The RPM gauge has numbers from 0 to 7 6 and 7 are Red. But sometimes when I am driving it goes past the 6 and 7 and the car is running fine.

Third problem is: When driving on the free way the speedometer was saying I was going 90 mph, but alot of cars were passing me. I pulled off the freeway and when at a complete stopand in the park position the speedometer said I was going 20 mph.

Fourth problem is: In the car there is climate control heating. The Diviers side heat doesn't work in the car. The air conditioner works fine but the heat. When turned on at the same level as the passenger side is drivers side is blowing cold air, while teh passenger side is hot.

Can I please have some suggestions to help me resolve these problems. Or where I can take it to get them fixed.

Thank You