If the valve underneath a 2003 gmc savana blowing hot/and still blowing hot air

You would need to start by checking pressures with a gauge. If you don't have a gauge you can rent on at the local auto parts store. If you are not too familiar with the ac system on cars you may want to bring this in for an inspection. Use this link to find a good shop near you. https://repairpal.com/repair-shops Alex