Chevrolet Repair: Low heat in cabin, 1990 cavalier z24, temperature thermostat


Question
1990 Cavalier Z24 3.1L auto 186k miles

Hi, this car has both very low engine operating temperature ( near the bottom of the gauge consistently), and consequently low cabin heat.  Last summer the heater core was replaced and the thermostat was replaced, I don't recall with what temperature.

I'd suspect a faulty sensor reading on the temperature gauge.... except for the low cabin temperature.   This has been going on for awhile not just since it's been so cold.

Any suggestions?  Is water restricted somewhere?   Do I have the wrong temperature thermostat installed?  It's the low engine temperature that concerns me the most.  

Thanks for any input.

Answer
Hi Brian,
I would be tempted to replace the thermostat again. I doubt that the coolant is restricted, or it would overheat.
Extremely low coolant level in the engine can register low on the temp guage, if coolant isn't surrounding the sender. That could also cause low cabin heat, so check the coolant in the radiator, not just the recovery tank.
Some thermostats are now designed so that when they fail, they are in the open position.
Van