1996 Explorer heating issues

I just had the heating plenum replaced because the blend door was broken. Now when I turn the a/c on it won't change to blowing out the vent unless I turn to max a/c, then I can turn it back to regular a/c or just air thru the vents. When I try to turn on the heat it stays cold until I keep turning the knobs, then maybe the heat will come on. My dad put the new plenum in and it was a big job, so I hate to bother him again. Does anyone have any ideas what could be wrong? Thanks

I would pull the Glove Box down look behind and check vacuum lines
it happened to me.
Hope this helps




I just had the heating plenum replaced because the blend door was broken. Now when I turn the a/c on it won't change to blowing out the vent unless I turn to max a/c, then I can turn it back to regular a/c or just air thru the vents. When I try to turn on the heat it stays cold until I keep turning the knobs, then maybe the heat will come on. My dad put the new plenum in and it was a big job, so I hate to bother him again. Does anyone have any ideas what could be wrong? Thanks