2000 Blazer LS 4.3L Auto 4x4 (102KMi) when I use the defroster selections on my dash selector the idle seems to shudder when the A/C clutch kicks in. What can I do to fix this it is currently just an annoying problem. I have the parts for a Tune-up (Cap Rotor Plugs Wires) if that is the problem.

TIA

 

I would start with the tune up first. If the contacts under the cap are corroded, it will cause a rough idle under load. Like when your a/c compressor kicks on. Same with the spark plugs, if the gap gets too big, it will also run like crap under load, especially at idle.