Good Morning,

I have a 2002 4-Cylinder Cavalier and a few months ago I noticed that once I hit 62 mph my temperature drops by 25%. Now, if I hit 40 mph my temperature drops completely. I get no heat when I turn on the vents. Any suggestions?

FYI: I know nothing about cars

 

Have your thermostat replaced. Its very cheap, won't cost you much. Your thermostat is a valve that opens to allow coolant into your engine when it reaches a certain temp. When a thermostat faults, they are designed to stay open at all times to prevent over heating. With the thermostat open all the time, your car will never heat up enough to produce heat because of the constant coolant flow.

Good Luck.

 

If after thermostat replacement this still occurs, have your cooling system backflushed. A plugged heater core will cause the same symptoms, even with a good thermostat.