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.
Pop radiator cap cold. Start the truck and let it warm up, have patience it might take a few minutes...2 to 5 minutes and watch coolant. It should be full all the way to top. Keep an eye on it, and when temperature gauge gets toward the middle, or less, watch for flow of coolant. If the coolant remains motionless after truck is fully at operating temp, the thermostat is bad, or water pump.
As for fan relays, they are in a separate box underhood next to fuse box drivers side. I could not find an image, but you can see it here Chapter 5 Page 135 http://www.manualowl.com/am/Chevrolet/2005-Silverado%201500%20Pickup/Manual/395
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