Why would my heat hand not work but when the fans don't it goes up on half why? on 2002 Nissan Altima

I've changed my 02 sensors, the sensor on the thermostat, thermostat and checked the fuses but still the heat hand won't work but sometimes the fans won't come on and the heat hand will go up half and fills like the cars running hot what should cause this?

Asked by for the 2002 Nissan Altima