By heater blower doesn't always work, plus the temperature selector hardly ever works either

Hello, start backwards from the blower motor. If the blower motor is not receiving power, then it won't blow. If it is receiving power and is still not blowing, then that's a problem with that component. If no power, checking backwards, trace to the point where the power to the blower motor is interrupted. As far as temperature selector, ensure the engine is getting to proper operating temperature, and then check the climate control temperature controls to determine if there is a problem present there.