Double trouble HVAC problem

[tbrew81]

Hi everyone.So let me get to it.About 3 months ago my fathers 97 expedition broke the blend door.Apparently a known problem in this gen.So he got a kit from heater treater to fix it.I've worked on everything from gokarts to f16s.So I told him I would help him install it.Started at it a early sat and finished that afternoon.He was pleased to be able to have ac again. All worked good til about 3 weeks ago.He said he got in one day and all it would do is blow out the defrost.Which to me would be a vacuum issue.But he also said that when he changed the temp, nothing would change.But as far as I can tell.Those 2 systems are independent of each other.Blend door is elec controlled and the air divertor is vacuum controlled.So my thinking would be either blend door motor as problem 1 and maybe a broken vacuum line in eng compartment for air divertor.I told him to check under battery for broken lines.Or could it be option 3 and be ac/heat control panel on dash.Going over this weekend to dive in for round 2.If anyone has any other ideas where to start or what and how to test would be much appreciated.Thanks