Recently, my temp. guage seemed to quit working. It seems to go just over 140 deg. then stops. Thought the sender unit was bad and replaced it, but no joy. Last night I drove the truck about 30 miles and the heater was putting out just warm air, much cooler than normal. After returning home the heater hose was warm, but not hot. Could it be the thermostat is stuck open and not allowing the engine to warm up. I realize it is mid May, but it is still winter here in WY. Any suggestions is greatly appreciated.

 

How how does the top radator hose feel? If it just warm got for the t-stat.