I have no heat

Obviously coolant is not flowing 'through' the heater core .. Check coolant level first, while engine is cold .. IF coolant level is FULL .. Have heater core itself flushed! .. I use air pressure and water combined to flush heater cores and it works 'very well' .. This needs to be done by someone that has a way to do this and knows how to do it properly! .. Option is heater core replacement.