Chevrolet Repair: low temp. reading on gauge, chevy 1500, radiator cap

Question
i have a 1993 Chevy.1500 z71 with 176000 miles the temp. gauge will not read over 100 degrees, i've replaced the temp sending unit and the sensor located on the intake manifold. what else could be the problem?  

Answer
Hi Mike,

I believe your thermostat is stuck open.  If it is open all the way and stuck, your motor will not heat up.  It needs to open and close slightly to maintain the temp it is supposed to.  

Could also be a radiator cap that is stuck open.  If the cap fails, the pressure cannot build up, and the temp cannot get high enough.  

A long shot is the fan is overcooling the motor.  Electric is on too much, or belt driven has a clutch that is not allowing for a freefloat.  

Hope this helps.

C J S