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2008 E350 4Matic
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Discussion Starter · #1 ·
I recently purchased. 2008 E350 4 Matic with 25,000 miles. Previous owner had the car serviced at the local MB dealer in Palm Springs. Heres my question/problem. When I start the car in the morning or any time it has been sitting unused for awhile the A/C comes on for about 4-5 minutes and then turns itself off even if I am not requesting A/C and the A/C switch is not on. There are lots of days where I don't need A/C so a bit frustrating that this happens. Before I go somewhere or park in the garage at night I always switch the A/C off a few minutes before turning the car off.
When the A/C is on I have never seen any water/condensation drip from the car which just doesn’t seem to be normal.
Any thought’s or suggestions…
 

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I recently purchased. 2008 E350 4 Matic with 25,000 miles. Previous owner had the car serviced at the local MB dealer in Palm Springs. Heres my question/problem. When I start the car in the morning or any time it has been sitting unused for awhile the A/C comes on for about 4-5 minutes and then turns itself off even if I am not requesting A/C and the A/C switch is not on. There are lots of days where I don't need A/C so a bit frustrating that this happens. Before I go somewhere or park in the garage at night I always switch the A/C off a few minutes before turning the car off.
When the A/C is on I have never seen any water/condensation drip from the car which just doesn’t seem to be normal.
Any thought’s or suggestions…
Check behind the trim and trace the wires of the AC unit it’s possible that a sensor went bad and they decided to hard wire it to the ignition fuse in the hood fuse box. If it isn’t there Please check that there isn’t a hard wire to the AC blower fuse the fuse at the driver side
 

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2005 E320 wagon
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I don’t know about hard wiring. These compressors are engaged whenever the engine’s running. Refrigerant pressure is moderated by valving and/or a swashplate in the compressor. It isn’t just an on/off signal to the compressor.

Sixto
05 E320 wagon 183K miles
 

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I don’t know about hard wiring. These compressors are engaged whenever the engine’s running. Refrigerant pressure is moderated by valving and/or a swashplate in the compressor. It isn’t just an on/off signal to the compressor.

Sixto
05 E320 wagon 183K miles
You can check at the back of the compressor and trace the wiring is it the sensor type of compressor or the manual one if it’s automatic you could switch to a manual one so when you turn on the engine it will only come on when you want it to also please check the controls at the time of starting a benz expert may be able to help you sort it out locally
 

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Dallas, Texas
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Compressor rests at about 10% delivery rate. Since it is always on there is some flow that keeps it lubricated.
In very low humidity climate there is no water dripping from evaporator.

 

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Compressor rests at about 10% delivery rate. Since it is always on there is some flow that keeps it lubricated.
In very low humidity climate there is no water dripping from evaporator.

I am guessing that you have the automatic compressor I do as well look into switching to a manual compressor if you’d like to have more control of it check your junkyard or let me know if you need further help finding one. Also monitor the oil level in the compressor

The modern sensors sometimes go bad sometimes a spray with electronic cleaner helps
 

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2005 E320 wagon
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Returning to the original post, how do you know AC is on? Or, what is your definition of on? As mentioned, AC is always on - negligibly, full tilt or somewhere in between. Two ways I can think to determine whether it’s “on”: air from AC vents is cooler than ambient, capable scanner shows refrigerant pressure or compressor controller signal.

On board diagnostics are robust on these cars, if there are no climate control faults related to AC compressor control and function, it’s very likely performing to spec.

Sixto
05 E320 wagon 183K miles
 

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2008 E350 4M, 2016 Audi Allroad, 2019 Audi Q5
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OP has not been seen since making his post. Let's wait for his participation. :)
 

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2008 E350 4Matic
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Discussion Starter · #10 ·
OP has not been seen since making his post. Let's wait for his participation. :)
I am finally back. I assume that if I feel cold air when I start the car its because the a/c is on even though the red a/c light is off. As mentioned after about 3-4 minutes i can smell that humid a/c smell you get when the a/c has been switched off. I have read a couple of posts on this and it appears this might be a normal condition. Advise was to just leave the a/c in auto and set the temp controls at 68 or 70 and let the heat/cool brain do its thing. As mentioned not a big issue but being new to this MB thing I thought I would seek advise from you experts. Next time I get in for a service I will ask to see if this is a normal condition or? As well never see any water dripping from the drain hose after the air has been on for awhile. I guess the only way to check the hose is when its on a lift or?
 

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2005 E320 wagon
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I guess your control panel is different from mine. My ‘05 AC panel has a switch labeled ‘AC off’ and lights when AC compressor is requested to not engage/not pressurize. When the light is off, compressor is fair game.

If you get it on a lift, make sure the drain hose is clear. It might be obstructed and that might be why there’s a musty smell. You only get condensate/water dripping when it’s humid. In dry climate, there won’t be much if any drip.

Sixto
05 E320 wagon 183K miles
 

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Mine does it too, it's perfectly normal. Even the big cooling fan behind the radiator will switch on some times along with the AC.
 
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