Pontiac Repair: no heat in Pontiac Montana

Question
I still have issue with no heat...I checked the coolant level in both rad and overflow and all OK...cabin filter is clear

Answer
Hi Ray:

try this when you go from full hot to full cold do you hear and or feel the air flow change somewhat? if so the tempature doo is working and then it is a matter of a issue with coolant flow into the heater core. if you do not hear the air flow change it's a HVAC door issue either a broken door or a bad actuator for the door.  if it's a flow issue with the coolant it could be a plugged heater core due to dirty coolant or a thermostat that is opening too soon aor stuck open and the flow is too fast though the cooling system and it's not absorbing the heat from the engine. does the temp gauge read in the normal range when it's not heating? does this van have rear HAVC if so do you have heat out of the rear unit? one last thing to do is to take the heater hoses off at the back of the engine and use a garden hose and flush the hoses in one direction and then back in the other direction to dislodge any debris that may have collected in the heater core. it act like a filter is there is dirt and debris in the system the passages are smaller then in the radiator so it's prone to get plugged up. good luck :-)