I just bought a 2004 trailblazer and the air conditioning didn’t work. It won’t blow out the top vents either which I assume is the mode actuator. What I can’t figure out is when you turn the ac on and it’s idling it will almost kill it then it will come back and keep cycling like that. The compressor isn’t locked up and it doesn’t even act like the clutch is trying to engage. Wiring issue? Not sure what to try next.