My sisters 03 buick rendeavous's heater isn't working... I know its not a truck but it's almost close.. The heater does not get hot and the temp gauge goes from 1/4 to 3/4 hot then rides at 1/4 etc... I tried to put a new thermostat in it WTF were they thinking with this design I will finish it tomorrow but I know I have heard of sensors going out that will cause this. Anybody got an Idea? It isn't throwing any codes.

 

Thermostat fixed it.... Heads up if someone driving one of these asks for a favor.... on em!!