Heat doesn't work
Try changing the thermostat it may be sticking or old and worn out
Yes, if the thermostat is not working, stuck open, then the engine can not get to operating temperature. You should notice this in the temperature gauge. Another way to tell is if the heater hoses are not getting hot. Also just check the coolant, may be low. One other thing would be with the climate control not working keeping the blend door closed.
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