josue villarreal, yes, it is possibly that it is your thermostat. It is also possible that your heater core is clogged or the your fan is not working properly to forced air through the heater care. Also, make sure that you have enough antifreeze in your vehicle. Check the heater hoses, the lower hose is where cooled coolant reenters the engine. it should not be cold but will not be as hot as any other cooling system component. If there is no circulation (hose, radiator and heater core cool) then you may have a bad coolant pump. If both hoses are hot that would mean you have enough flow through the core, check the servo that opens and close the vent doors. If they do not open properly, you would not get enough flow to heat up your interior.. Hope this helps, good luck.
+
== Update ==
+
Just looked at the service manual for your specific model. thanks for letting us know which one it is. Check your Temperature Flap cable. Make sure that it is properly adjusted.
+
Temperature flap cable, installing and adjusting
+
Prerequisites:
+
Heating and ventilation controls are installed.
+
Connecting duct removed
+
Turn temperature rotary control knob to left onto stop.
+
Attach center wire of cable -1- to the temperature flap lever -2-.
+
Push temperature flap lever -2- to stop -arrow A- and secure outer cable -1- with clip -3-.
+
Turn temperature rotary control knob to left and right onto stops.
+
When turning the rotary control knob, both end stops must be reached.
josue villarreal, yes, it is possibly that it is your thermostat. It is also possible that your heater core is clogged or the your fan is not working properly to forced air through the heater care. Also, make sure that you have enough antifreeze in your vehicle. Check the heater hoses, the lower hose is where cooled coolant reenters the engine. it should not be cold but will not be as hot as any other cooling system component. If there is no circulation (hose, radiator and heater core cool) then you may have a bad coolant pump. If both hoses are hot that would mean you have enough flow through the core, check the servo that opens and close the vent doors. If they do not open properly, you would not get enough flow to heat up your interior.. Hope this helps, good luck.