93 ranger will not blow hot air

[chogeberg]

I have 1993 3.0l 2wd and it will not blow hot air and my temperature gauge is all over the place when I drive from warm to cold will not stay constant. After driving my truck the hoses to the heater core are still cold. On A whim I removed a line to a sensor next to the thermostat and the truck started blowing warm air but not hot like it should. Any suggestions and what is that sensor. Also is there anyplace to look up what what sensors are what on the engine. Haynes and Chiltons are no help.

 

[XLTsplash]

I would start be making sure your cooling system is full and has no air pockets. when the engine has been running for a while and is warmed up. Feel the upper a lower radiator hoses. They should both be warm. If not, replace the thermostat. If the engine never warms up replace the thermostat. If you replace the thermostat make sure you get all of the air pockets out.