Ac is always on
MBworld Guru
Joined: Dec 2009
Posts: 10,782
Likes: 1,011
NO LONGER ACTIVE
Do you mean that the compressor is running? That is normal. It does not use a conventional clutch - it has an internal "swash plate". If you mean that the ventilation fan continues to run, then you may have an issue.
Senior Member
Joined: Jan 2018
Posts: 295
Likes: 24
From: Edmonton Area
2007 CLK550 Coupe, 2003 CL600, 2012
So if it has a swash plate, how does it handle the on/off cycles? Does it vary its pitch somehow or stroke length?
MBworld Guru
Joined: Dec 2009
Posts: 10,782
Likes: 1,011
NO LONGER ACTIVE
Yes, when activating the front defrost function, the compressor is engaged. The swash plate AC compressor actually gives it the ability to vary its compression ratio. Based on the swash plate position, the piston strokes can vary from very shallow (basically no compression) to very deep (full compression). The advantages of this are that the compressor's displacement can be varied based on cooling demand, and in turn, that can help with engine efficiency.
Senior Member
Joined: Feb 2015
Posts: 434
Likes: 16
From: Midlands, UK
CLK W209
I don’t know why you wouldn’t just keep the AC on constantly ... in the U.K. winter it’s not long before the car is fogged up due to the humidity, and any loss of efficiency is negligible. It’s far easier to adjust your driving style to regain a far greater economy benefit.
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Junior Member
Joined: May 2008
Posts: 53
Likes: 6
From: New York
2007 clk550, 2006 clk500 (sold)
I prefer not having AC on constantly. To turn off AC completely after any use to cool down the interior, I turn the climate control off & then use the climate control system as usual.
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