My variable displacement air conditioning compressor has recently started making a very very loud knocking noise when it is engaged. It is almost louder than the engine but still cools and operates perfectly fine except for the noise. It does not sound like a bearing noise but it sounds almost as if the piston is banging against something at the end of every stroke. If anyone has any ideas what could be wrong with it, please chime in.

Thanks

-Ali

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record