2000 Envoy heat-A/C problems please help.

[Banksno925]

Hi guys,
I have had a lot of problems with my 2000 envoy heat a/c. I have gotten it to the point where it now works but the blend door motor constantly cycles. So if I put on a/c it blows Hot air then cold air constantly switching every 30 seconds. So I tried to unplug the blend door motor to get it to stop on one position hot or cold. It worked I stopped it on a/c and now get cold air. So I don't know if it just needs to be realigned I did take it out and put it back in. Any idea's ?

Problem 2. While getting to the blend door for the 5th time. When I unplugged the vaccume thing that controls my vents I snapped the end of the plastic arm off. Its a plastic arm that controls my vent routes. When u 1st drop glove box and have to unplug and move the vaccume to get to blend door. Well the hook that connect the vaccume to the vent controle snapped. Now what ? I mean it makes me not even want my truck because of this dumb problem ? How would I even go about getting that arm ? and how would I replace it ? I don't think glue would hold it because the part that snapped is constantly pulled on to redirect vents. I don't know what to do any suggestions ? Thanks for your time I know its probably hard to read all this.