98 Jimmy Heating / Air conditioning Cycling

[Handy!]

I developed a heating air conditioning cycling issue , all the controls either on auto or manually set it, cycles very hot air then seconds later cold air. with the system of I can hear a vacuum pot cycling. I checked out all the vacuum hoses and all are in good shape. all vacuum pots and plungers (2 ea.) seem to be working ok.

Does anyone have any experience with this issue and if so what was the fix?

 

[Morbugs]

i will be watching this thread, Mine wont go off 'heat' ,, doesnt matter if I turn temp all the way down to cold it is blowing hot
i fixed the vacuum lines that control the vents/ floor/ defrost --