A/C works great, but...

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04EddyExpy

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My AC blows nice and cold, but I’ve noticed that whenever I start the engine when it’s cold, and the A/C kicks on, something shudders down in the engine bay. I can hear it and feel it. Just for a second, then the A/C comes on normally. I live alone so I haven’t had the chance to check it with a friend. Is it the compressor, I wonder?
 

Sgt Darkness

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It could be the clutch on the compressor but I would get someone to help you identify exactly what the problem is before making any repair decisions. Let us know once you identify the problem(s).
 

ManUpOrShutUp

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The CASS perhaps? That drove me nuts when I first got my truck and the local dealer had no idea what it was.

Compressor Anti-Slugging Strategy (CASS)

Liquid refrigerant may accumulate in the A/C compressor under certain conditions. To alleviate damage to the A/C compressor, Compressor Anti-Slugging Strategy (CASS) is utilized.

CASS is initiated only under specific conditions:

  • Ignition is off for more than 8 hours
  • Ambient temperature is above -4°C (25°F)
  • Battery voltage is above 8.5 volts during engine cranking
When these conditions are present, the PCM will activate the A/C control relay prior to cranking of the engine. The A/C control relay engages the A/C compressor for approximately 4-15 A/C compressor revolutions or a maximum of 2 seconds (depending upon vehicle application), allowing the liquid refrigerant to be pushed from the A/C compressor. CASS is initiated by the PCM regardless of the HVAC system settings.
 
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04EddyExpy

04EddyExpy

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Sorry I haven't followed up on this -- it happens fairly infrequently enough that I haven't been motivated to go have it checked out, lol
 
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