I have a Trane R-22 60-ton CGAF chiller w/ 2 refrigerant circuits with 3 fans for each and the first-stage condenser fans have motorized dampers. It was working okay until the weather cooled down recently. I had a service call to the chiller this morning and circuit #1 was off on low pressure trip and circuit # 2 was off on "compressor trip". When I started the chiller, circuit # 1's head pressure rose up above 320 psig before the 2nd & 3rd condenser fans came on and then the 1st condenser fan damper opened. Then the head pressure dropped rapidly down to 155 psig, then rose above 320 psig (swung back & forth) . Tried activating circuit # 2 to get chilled water to the bldg and it had similiar symptoms with the pressure rising slightly above 300 before the 2nd & 3rd condenser fan on and the damper for fan # 1 opened up. Then the head pressure dropped down to 155 psig and display read "compressor trip" for that circuit. Does anyone have any suggestions? I tried adjusting the head pressure ctrl on the display to the same settings as two other CGAF chillers nearby, still have the big swings.