W124 - power loss when A/C kicks in

Peter C1974

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Further to this post: http://forums.mercedesclub.org.uk/showthread.php?t=119932

Switching the a/c on whilst driving I can feel an instant power loss as the compressor kicks in. The a/c blows ice cold. The engine idles fine with the a/c switched on. The a/c seems to work in pulses, as it blows cold the power loss occurs, then it's fine again, then it happens again...

I understand that the compressor saps some power from the engine but I am concerned that there is a problem when I can feel power losses occurring. I am also concerned that the serpentine belt is being put under additional stress when the a/c kicks in.

Do I have a problem?
 

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Wow, this is a hard one and I have never heard of this before, is the belt loose
 

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Perfectly normal operation. Early compressors were either on or off, and the drag down on the engine quite normal.
 

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For extra power my Scorpio Cosworth used to switch of the air con on WOT (wide open throttle).
 

kth286

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Perfectly normal operation. Early compressors were either on or off, and the drag down on the engine quite normal.

It would still have an electro-magnetic clutch I would have thought, and therefore the feel of 'sudden' switching should not occur. It should be a gentle switch on and off, and therefore nil jerk on the belt.

Possibly a sticky clutch mechanism ?
 
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It would still have an electro-magnetic clutch I would have thought, and therefore the feel of 'sudden' switching should not occur. It should be a gentle switch on and off, and therefore nil jerk on the belt.

Possibly a sticky clutch mechanism ?

The clutch is either on or off, the same as the electro mag clutch on a 102 fan system. There no way to regulate the power to the magnet to get a soft enguagement.
 
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Peter C1974

Peter C1974

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I can feel the engagement as the engine loses power but I wouldn't say the engagement is jerky or abrupt.
 

grober

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Possible that your compressor is requiring too much power to function. Might imply its on the way out worn bearings / dry of oil etc? IS THIS A CHANGE IN BEHAVIOUR FROM THE PAST? They always draw some power and this is more noticeable on smaller capacity engines that produce little torque at low revs- diesels are usually better in this respect.
 
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Peter C1974

Peter C1974

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Possible that your compressor is requiring too much power to function. Might imply its on the way out worn bearings / dry of oil etc? IS THIS A CHANGE IN BEHAVIOUR FROM THE PAST? They always draw some power and this is more noticeable on smaller capacity engines that produce little torque at low revs- diesels are usually better in this respect.

I've only had the car for a few weeks so I can't say if the a/c is behaving any differently.

The a/c has been regassed recently and works well.
 


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