This forum is great and I do appreciate the support (lessons learned)
by all.
I have a 1995 Cherokee, when the A/C is running I get a rumbling noise
(almost fog horn sound) from under the hood. Not constantly. I have
found the noise comes from the dryer (I think) as it vibrates. Bring
the RPM's up or switch the A/C off and it quits. Any ideas? I
recently had the system evacuated and recharged. I was told I had
overcharged the system and this was the pressure release valve making
the noise.

Well, I still have the noise at times.

What is the culprit?

Dano