This is the season for A.C. questions, so here goes. After getting the R-12 recharged in my '88 Chev C1500, the A.C. works great, but the compressor makes a lot of noise when the clutch is engaged. I read if the system has too much refrigerant that liquid R-12 can hit the reed valves and cause a clatter. It does sound like a high pitched "card in the bicycle wheel". If this is the case, can I easily let out some freon to correct? Any other ideas? The shop that recharged it says it just normal noise from an old compressor, but it wasn't this loud before. von