only heat blows in front but heat and ac in back.

What is your question?

only heat blow out of the front vents but heat or A/C will blow out of the rear vents. The front use to work if you turned the temp control from cold to hot and back a few times but doesn't any more. And there is a sound coming from under the dash.. like a ggrr ggrr ggrr.. it comes and goes.

What makes this problem better or worse?

nothing now

How long has your 2002 Chevrolet Suburban 1500 had this problem?

about 2 since it started