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  #1  
Old 08-07-2016, 11:01 AM
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A/C troubles on 350sdl

So my a/c was working perfectly until last week. On idle the compressor shuts off completely and only kicks in above 1800rpm. The only thing I can think of is that something is giving a false rpm reading.

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  #2  
Old 08-07-2016, 11:20 AM
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That sounds logical... and there are lots of threads addressing that kind of situation..
but I have no FSM's for that late a car.....someone will show up soon... a slow weekend.. people may be watching the Olympics... check the search /archives for potentially faster answer...
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  #3  
Old 08-07-2016, 05:24 PM
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What are your pressures? Do your Aux fans run at idle?

May be the speed sensor on the compressor going out, klima relay problems, or serpentine belt slippage if pressures are good.
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Last edited by bsmuwk; 08-07-2016 at 05:36 PM.
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  #4  
Old 08-07-2016, 10:11 PM
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Quote:
Originally Posted by leathermang View Post
That sounds logical... and there are lots of threads addressing that kind of situation..
but I have no FSM's for that late a car.....someone will show up soon... a slow weekend.. people may be watching the Olympics... check the search /archives for potentially faster answer...
I did a search and didn't come up with anything, I'll keep checking

Quote:
Originally Posted by bsmuwk View Post
What are your pressures? Do your Aux fans run at idle?

May be the speed sensor on the compressor going out, klima relay problems, or serpentine belt slippage if pressures are good.
Pressures are optimal and the Compressor is brand new as the clutch was giving out and it comes with a new sensor attached. The fans kick in once the compressor engages, Klima relay is good as it has been tested on my other 350SDL and the belt, tensioner and tensioner dampener are new as well.
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OBJECTS IN MIRROR ARE CLOSER THAN THEY APPEAR, ONLY IN A BENZ

89 560SEC
90 350SDL (Rudolph)
91 350SDL (300SDL drivetrain)
87 BMW 635CSi (Swanhild)
89 BMW M6 (euro)
99 Suzuki Hayabusa (Only the fastest thing ever)
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  #5  
Old 08-07-2016, 10:22 PM
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I would get a test LED rigged up to the coil similar to what Jeremy5848 did on his 124. Let's verify if the problem is electrical or mechanical.
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The OM 642/722.9 powered family
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2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

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  #6  
Old 08-08-2016, 01:44 PM
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Originally Posted by jay_bob View Post
I would get a test LED rigged up to the coil similar to what Jeremy5848 did on his 124. Let's verify if the problem is electrical or mechanical.
So what I did today was swap out the compressor to the other 350sdl and it works perfectly, I'm confident that it is an electrical issue with engine rpm (my tach is functioning okay).
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OBJECTS IN MIRROR ARE CLOSER THAN THEY APPEAR, ONLY IN A BENZ

89 560SEC
90 350SDL (Rudolph)
91 350SDL (300SDL drivetrain)
87 BMW 635CSi (Swanhild)
89 BMW M6 (euro)
99 Suzuki Hayabusa (Only the fastest thing ever)
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  #7  
Old 08-08-2016, 03:17 PM
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I would make sure the tach signal is showing up at the right pin on the Klima. And the speed sensor from the AC is showing up on its pin.

The Klima does a comparison between the two so if one of the signals is missing it can't get the agreement.

Also make sure you have the right Klima, since you switched engines, the ratio between the engine speed and the compressor speed may be different than the stock engine.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech
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