Re: A/C tapping sound
You probably have the problem fixed by now but I'll add this for anyone else in this situation as it may help. I had a tapping sound coming from the air compressor area also. I eventually figured out that the serpentine belt had stretched just enough to allow the idler pulley assembly to rap against it's mounting bracket under certain conditions, like when turning on the AC or having the clutch kick in. I thought for sure it was the AC compressor, it was a pretty loud tapping too. Drove me crazy trying to isolate it. With a new serpentine and a 5 minute swap I was good to go. :-)
I sold the liberty after 7 years and have a Grand Cherokee now but that liberty was a very reliable vehicle (except for the power window lift assemblies... eventually just bolted the rear windows up as I never used them).