2017 potential A/C condenser issues at high altitude??

[cumminbighorn06]

My truck lives at sea level since new for the last 2 years. Recently took my truck up to high altitude in Sequoia national park, and I while driving up through the pass running my defroster ( which cycles AC) I heard what I can describe as a split second crunch sound and hesitation come from passenger side twice intermittently . Was wondering if due to elevation change, and cold temperatures was the pressure in my A/C compressor affected some way?

 

[Tuesdak]

Not a problem.

The sound is nothing that hurts our AC system design. What you are hearing is the compressor slugging the liquid R134a that condensed in the coldest and lowest parts of the system. The compressor is located low on the engine to improve oil return with R134a (vs. high mounted on the engine R12 designs that had better oil return with the R12 vapor.) So the low point of the system is the compressor and it gets cooled by airflow generally when the engine is off and sitting. (High mount R12 compressors were in the "hot" upper area of the engine and not the coldest part of the AC system.) This causes liquid R134A to condense in the cylinders and suction side of the cold compressor. Then the liquid will "slug" the compressor with the "thump" you hear when it kicks on. You can't compress a liquid so the compressor nearly suddenly stops for a moment with a "THUMP!" as it pushes the liquid out.

GM on the other hand has this low on engine compressor design breaking compressor belts, ripping the tensioner off the engine, and blowing compressors in half. GM redesigned the belt drive to an elastic belt with no tensioner in later model years...