I had the same problem. relaced the tep control sensor and sending unit and it worked. One is located next to the thermostat housing and the other is further over on the intake.
The heater valve may not be engaging or the heater core may be blocked.
The temperature of the coolant entering the heater core is controlled by the engine thermostat. The engine coolant thermostat is generally located at the engine end of the upper radiator hose.
no heat can be caused by,blocked heater core insufficient coolant in engine blocked heater hoses from engine to heater core bad heater thermostat bad thermostat in engine bad heater control switch
you probably need to flush system including heater core.AnswerSometimes the metal in the thermostat corrodes and breaks down so the stat stays open, unable to close....causing the engine to run cool at all times and reducing the efficiency of the heater. Remove it and check it. I have the same problem, I replaced thermostat twice, flushed system and replaced sensors, it did not fix problem, still searching for an answer.^^^^ To this guy, its probly your Coolant Temp. sensor.
Check your heater core. ANSWER I'm not a mechanic but isn't the thermostat supposed to be a 190 F unit. With a 160 F the engine would run cooler , read cooler on the guage, and the heat from your heater wouldn't get as warm as it should ( just like what happens when a 190 degree F. thermostat sticks open )
Check into the temperature control valve--this is different than the thermostat.
Check both the supply and return heater hoses from engine to heater for blockage or clogging: remove them and flush. Also check the inlet and outlet pipes on the engine and heater core for gunk buildup and leakage.
The block heater on a 1995 Ford Ranger is in the engine space under the hood. The plug for the heater block is located near the front of the engine.
The defrost is cooing your coolant by circulating the fluids through the heater core. Check the water pump to insure that its pumping and check the radiator for blockages in the fins. Also check for an air bubble that can happen when a thermostat is replaced.
The heater cor was replaced but it is still not getting warm
If a thermostat is not working properly, you cannot calibrate it. It must be replaced.
If your engine thermostat sticks open it will run cooler on your temperature gauge and you won't see the temperature gauge go up to the point where your engine thermostat opens and then the temperature gauge will show a drop in temperature , your check engine light will probably come on , your gas mileage will be less , the heat from your heater probably won't get as hot If the engine thermostat were to stick in the closed position your engine will overheat ( but there are several other causes for an engine to overheat )