C4 heater

My 89 C4 heater has what feels like outside air coming out of the vents no matter where I set the temp or auto -mannual control. Both heater hoses feel hot. A/C works great.Would appriciate any ideas as moving south is not an option right now :cool:

My 89 C4 heater has what feels like outside air coming out of the vents no matter where I set the temp or auto -mannual control. Both heater hoses feel hot. A/C works great.Would appriciate any ideas as moving south is not an option right now :cool:You may want to try one thing. It may be a vacum problem.That is if you have you have an automatic clim, control.Check the HVAC valve. IT should be in the engine compartment at the back on the passager side at the end of the intake manifold. It goes on the manifold and should have two small tubes going to it. Check and see if is crack or small holes on the part. That fix my problem on my 1994 after all most takeing the hole dash apart and finely look under the hood and found the part had small holes in it causeing vacam leak. hope this helps.