2000 Cadillac Deville Erratic Compressor Operation

Cadillac Deville was sent to shop from another facility with complaint of a/c cycles off and will not come back on for several minutes and vent temperature goes warm.

Checked codes and none were stored in the ECM, DIM or IPM. All data looked good and then the compressor cycled off after running at 2000 rpm for about 10 minutes. Data still looked good including clutch relay request and actual condition.

Tested clutch relay signals at relay base with voltmeter, all tested good. Clutch cycled back on while testing so I had to run again for extended time for complaint to return. Double checked and all signals were present at relay.

Raised vehicle and performed visual inspection. Spotted a sensor at rear of compressor. Consulted Mitchell On Demand and found nothing listed. Went up to 2004 looking for reference to sensor and finally found it. Sensor turns off compressor at 311 degrees and is outside of computer control or diagnostic ability.

Checked to see if system was overcharged. It was actually undercharged by 8 ounces.

While system was recovered I inspected the orifice tube only to find debris on the screen. Replaced tube and recharged system to confirm what I already knew. The compressor was coming apart and the condenser was restricted. I confirmed this by doing a temperature drop test at the condenser input and output lines. 80 degree drop at 2000 rpm after 1 to 3 minutes. Way too much.

System needed the compressor, condenser, accumulator, orifice tube and compressor hoses replaced. Discharge hose had been leaking and suction hose had been updated. Flushed the evaporator and remaining lines. Added oil, vacuumed and recharged system. Works perfect!!!!!!!

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