washing machine water temperature selector dosent seem to work?

Check the inlet filter screen on the hot water hose first.Then check for power to the cool/cold and warn/cold solenoid(s)? Sometimes you can adjust the temp setting and "hear" the solenoid click. I have seen a 4 solenoid combination valve with debris in the valves. If you feel mechanically inclined take apart this combination valve and clean out any debris. especially if you hear the "clicking" and do not feel anyTemperaturee changes. Really need more informationn. I might be steering you in the completely wrong direction. Age, Brand and Model/Serial numbers are always helpful in questions regarding problems with any machine

what brand is it? if it isnt a really high end brand then it is more than likely the temp switch. the only other problem it could be is the water valve but since the hot water does come through when set to hot/cold that tells you the valve is working.