Replace the Thermostat on a Chevy Truck
If your car is running cold, a bad thermostat that is stuck open or opening at too low of a temperature is your prime suspect. this video shows how to replace a thermostat on a 4.3l V6 chevy engine. The thermostat for this truck only costs about 4-5 dollars so it is a cheap fix.
The truck in this video is a 1991 Chevrolet C1500 Scottsdale with the 4.3L V6.