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#1
06-14-2009, 11:30 PM
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w124 e420 ac compressor and cruising
This may or may not have a quick answer:
When cruising on the highway with the ac on, I can actually feel a 'loss in power' from the car every time the ac compressor engages (once or twice a minute). Is this normal? I know that running the compressor loads the engine quite a bit but I don't ever remember being able to feel it while cruising at 75. Car is a '95 e420. Let me know what you think. Thanks!
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1995 E420 1998 SL500 Sport 2009 E350 Sport 1995 S500 Coupe 1992 500 SEL 
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#2
06-15-2009, 07:42 AM
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Can't help you solve the condition, but it's not normal to be able to detect the cycling of the A/C compressor in the way you describe at freeway speeds. That's true even in my 2.6L engine, and it has to be true in your much more powerful V8.
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1988 California version 260E (W124) Anthracite Grey/Palomino Owned since new and still going strong and smooth MBCA member Past Mercedes-Benz: 1986 190E Baby Benz 1967 230 Inherited from mom when she downsized 1959 220S Introduced me to the joys of keepin' 'em goin' There are only 10 kinds of people in the world--those who understand binary and those who don't
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#4
06-16-2009, 06:29 AM
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How does the A/C system cool? If you still get nice, cold air maybe it's just time for a tune-up.
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"It's not about how fast you can go, but how well you can go fast." Bob in Richmond '97 S320 (LWB), Ruby Red Metallic, 73k miles '97 S420V, Smoke Silver Metallic, 155k miles
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#6
06-16-2009, 04:17 PM
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As to why the a/c is cycling, the original poster lives in Minnesota - it just ain't that hot up there! So no concerns there.
Can't comment on whether it's normal to notice the cycling. I certainly do in all my cars - but none of them are/were V8 engines.
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#7
06-16-2009, 04:44 PM
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The compressor will only cycle if the evaporator starts to freeze. It normally won't do that because the control valve will destroke the compressor if the demand is low. (There is not a cycling switch in the low-side line.)
Your system is probably low on refrigerant. Or very high, as overpressure will stop the compressor. That's why I say that it is important to know why it is cycling.
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#8
06-16-2009, 10:43 PM
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It's cycling because it's a 124. They don't have variable displacement compressors. This car has a Nippondenso 10P17 variant. With this setup, if it's not very warm out the evap eventually pulls down near freezing and the compressor is cycled off to avoid icing. It's quite normal operation for this model.
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#9
06-17-2009, 12:05 AM
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Quote:
__________________
1995 E420 1998 SL500 Sport 2009 E350 Sport 1995 S500 Coupe 1992 500 SEL
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Linear Mode
