I have a 2005 Buick Terraza with 68,000 miles. The A/C compressor clutch will not engage. I can bypass the compressor clutch relay and the compressor clutch engages and the A/C works great. I have checked the relay for continuity and I even replaced the relay. The new relay and the old relay have the same resistance. I have disconnected the battery in hopes of resetting any computer faults. That didn't help. Where do I begin to determine why the computer won't turn on the compressor? I have insured that the A/C controls are set on max A/C, the climate control knobs are set to max cooling and the A/C light comes on. The fuses are OK. When I bypass the compressor relay I use the compressor relay fuse as part of the circuit. Help Please!