heat does not come out?

Hello, if the engine is getting to proper operating temperature -- which it seems so based on your concern description and the fact it works for a day sometimes -- then it sounds like a temperature control concern inside the vehicle. There are doors and motors that control air flow direction as well as air temperature inside the vehicle. If there is a problem with one of these doors or motors, then you could get stuck in the "all cold" position. This warrants looking at -- have your dealer recheck their work, or seek the guidance of a different local shop near you: www.repairpal.com/repair-shops