Dodge Repair: 2003 Durango with dual a/c: Clicking souns from compressor

Question
I have a 2003 durango 4wd with a 4.7 and dual a/c. I have a two part question. First, when i turn on the a/c the compressor makes noise that sounds about like the noise you'd get when you put a playing card in your bicycle spokes back in the day. Maybe just a little bit louder. I'm assuming it's compressor valve noise. It does cool however it feels like it lacking but not lacking much (this test was done for 5 min at 65mph). The low side reads approx.75psi with a bouncing needle to the plus 2.5psi then to the minus 2.5psi with 75psi in middle. the high side reads 195psi. all readings given were taken at idle speed, front/rear windows down, front/rear a/c both on max with highest blower speed setting with an ambient temp of 97F (heat index a little more). If i increase rpm to about 1700 the low side drops about 10psi (needle still surging of course) and high side increases to about 215 to 220psi (needle doesn't surge and never did). I am leaning heavily toward compressor replacement because of noise and low side needle surging but wanted a second opinion. I didn't know if I had an expansion valve problem and if so could it report to the compressor causing the noise (never know it to be the case in the past). Also I believe the rear a/c expansion valve to be located under the vehicle above the muffler and muffler's heat shield, is that correct (outside of cab not inside)? Lastly if I replace the compressor, is the condenser able to be flushed or is it the type requiring replacement?

Answer
Hi Kris,
The '04 Durango manual that I have on CD has 500+ pages just about the HVAC system, including 325 pages about the self-diagnostic trouble codes that might be worth trying to recover using a diagnostic readout box to locate the B-prefix codes. Let me know if you try that and the results.
Other than that I am not much of an expert on AC, it appears to me that the high pressure readings you are showing are quite low (should be 250 - 350 psi at the ambient and rpm's that you are running at, while the low side are normal to slightly high. According to the manual: that might simply be a too low a charge of refrigerant and the clicking might be due to valve cycling that occurs at the cut point when the compressor is about to be cut off. If that doesn't correct it then it is possible that there is a flow restriction through one of the two evaporators, and if not that then the compressor is suspect, in that order.
So you might try adding some refrigerant to see if that corrects the noise. The rear expansion valve is in the cabin according to the drawings showing that unit, not under the floor. I didn't see a mention of the condenser needing to be replaced is the compressor is replaced.
Because AC noises are sometimes difficult to correctly diagnose you might do well to go to an AC shop and have them listen and find out what their diagnosis is before or after adding refrigerant to the system.
Please read the PS (below) and respond to it,
Thanks,
Roland