My A/C has been working off and on but lately not working at all. Today I pulled the vacuum check valve off the intake manifold the removed it from the vacuum line. I could hear the vacuum release, I then re installed it and started the Jeep and A/C works fine. I shut the engine off, restarted it and again the A/C didn't work. Performed the same procedure and it works again. Is that check valve possibly bad????