I installed the Four Seasons Deslugger in 2015 on our 2005 Yukon with rear AC when I installed a new compressor (exiting compressor kept breaking the belt), as a precaution. I removed the Deslugger - which just installs in series to the compressor wires, custom end harnesses - about 3 weeks ago before I sold the 2005, and installed it onto our newly-acquired 2011 Yukon.
From https://www.4s.com/en/marketing/the-deslugger
The Deslugger is a patented compressor clutch timer that is designed to help prevent “slugging” in low mounted compressors after the vehicle has been sitting idle for over 30 minutes or longer. Upon the next start up, The Deslugger is designed to gradually push oil or liquid refrigerant out of the compressor before it fully engages, relieving the possibility of a catastrophic system failure.
Compressors on many modern A/C systems are mounted low down on the engine. This location leaves the compressor prone to liquid “slugging.” When the vehicle sits, oil and liquid refrigerant collects in the compressor body. The result can be hydraulic lock with catastrophic compressor damage on initial compressor engagement. Four Seasons Problem Solving Part, the Deslugger, eliminates this issue.
Extend compressor life by eliminating liquid "slugging" with the Four Seasons Deslugger!
The Four Seasons Deslugger solves this liquid “slugging” problem by pulsing the compressor clutch multiple times during initial engagement. By gradually engaging the compressor, trapped liquid is gently moved out, preventing catastrophic hydraulic damage. Once the brief deslugging function is complete, the compressor reverts to normal cycling operation until the system has been off again for more than 30 minutes.
U.S. Patent No. 9,377,014 U.S. Patent No. 9,796,248