how to tell if themo. is opening properly
besides sqeezing the upper radiator hose to feel for water flow, is the a better way to test thermostat without removing it and testing?? truck is a 2005 Silverado 5.3 vortec with 107k miles, and is there a fan relay sensor that gets faulty. fans seem to only come on when air is on, now...... any advise out there?? thanks, kmac.