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FAN RUNNING HIGH CONSTANTLY With AC ON

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Old 06-19-2010, 10:45 PM   #1
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Exclamation FAN RUNNING HIGH CONSTANTLY With AC ON

When I have the AC on, The Fan by the Radiator staying running at the Highest Speeds!!! Doesn't slow down or turn off until I turn the AC Off. This doesn't happen under normal driving conditions with No AC running.
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Old 06-20-2010, 07:22 AM   #2
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This can be a number of issues such as faulty A/C pressure/temperature switch, damaged dash contol unit, up to & including the fan controller module.

The first thing to check is that you have a full & correct refrigerant gas charge in the system. You obviously have some gas or the A/C would not start at all. It has a protection circuit to protect the compressor. Check refrigerant first.
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Old 06-20-2010, 01:02 PM   #3
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quick question..does the fan turn on IMMEDIATELY when you turn the AC on or takes a short amount of time afterwards?
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Old 06-20-2010, 06:13 PM   #4
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A little lag, especially when you put it on full blast.
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Old 06-20-2010, 07:33 PM   #5
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Norwich,...Yes it takes a little while about 30 seconds before it goes on.
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Old 06-20-2010, 08:41 PM   #6
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Canít unequivocally claim itís Ďnormal,í but thatís exactly how my '02 behaves.

Shortly after a cold start, with ambient coolant temperature and the HVAC system switched on (not in Ďeconomyí mode), the radiator/condenser fan is promptly energized. Otherwise, itíll only activate when coolant temperature substantially exceeds the thermostatís nominal (excluding those on M272's) 87į Celsius opening threshold.

Thereís a switch on the high pressure side of the air conditioning compressor circuit (cattywampus from the radiatorís drain petcock) that signals fan operation -independent of coolant temperature- when refrigerant pressure exceeds ~12 bar.
Itís a PWM signal, so full fan speed typically occurs only when more than 20 bar/290 psi has been achieved.

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Old 06-20-2010, 08:51 PM   #7
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Splinter Will this cause the Fan to NEVER turn off? Because it never turns off with the AC on.
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Old 06-20-2010, 09:18 PM   #8
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Quote:
Originally Posted by taylortech View Post
Splinter Will this cause the Fan to NEVER turn off? Because it never turns off with the AC on.
You should take it to the dealer and make them run StarDiagnosis on it. Maybe it's only a thermostat valve malfunction.
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Old 06-20-2010, 10:34 PM   #9
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you do live in florida and it is the middle of summer, I dont pay attention to my fans but I dont think them working hard to keep the engine and a/c cool in 100+ degree temps sounds out of place.
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Old 06-21-2010, 07:07 AM   #10
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splinter - You are correct - the fan should kick in immediately. It should not however run flat out & be intrusive until set trigger points you explain. I took it that the OP meant the fan was running at max. Assumption is the mother of all f---ups.
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Old 06-22-2010, 12:56 AM   #11
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Quote:
Originally Posted by taylortech View Post
splinter will this cause the Fan to NEVER turn off [of high]? Because it never turns off with the AC on.
It certainly could.

Yes, the fan should be running whenever the HVAC system is switched on, again excluding Ďeconomyí mode. Note the air conditioning compressor is often active in every other setting for its desirable dehumidifying properties. It shouldnít necessarily run at its maximum speed whenever itís engaged, however. Probably little harm in doing so, particularly in a tropical climate like yours, other than increased amperes draw and potentially decreased fan motor life.

In typical German fashion, the sensors, circuits, and programming that regulate the fanís speed seem overly complicated. Troubleshooting malfunctions is no picnic. Only know about the B12/2 sensor because my fan didnít activate when the air conditioning was switched on, thereby reducing low (vehicle) speed cold air output. The condenser must have sufficient airflow across it in order to maximize its effectiveness. As an aside, I had the fanís (coolant temperature) activation threshold lowered -and its speed increased- via Star DAS in an effort to mitigate excessive heat soak that negatively affects its supercharged engineís performance. Howls like a banshee most of the time; doesnít bother me in the least. A pleasant side effect is even cooler cabin AC output.

Quote:
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..It should not however run flat out & be intrusive until set trigger points you explain. I took it that the OP meant the fan was running at max. Assumption is the mother of all f---ups.
Sir, I believe youíve indeed interpreted his post correctly. Me thinks this thread is another shining example of my f---ups!

Last edited by splinter; 10-06-2010 at 07:02 AM.
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Old 06-22-2010, 06:08 AM   #12
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On my 240 the fan very seldom runs flat out. On a very hot day after a stop & heat soak with AC on flat out it will crank up to full speed. I find the fan extremely obtrusive running flat out. The thing actually heterodynes producing a pulsating din. I don't like this.
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Old 06-22-2010, 10:46 PM   #13
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Quote:
Originally Posted by Glyn M Ruck View Post
On my 240 the fan very seldom runs flat out. On a very hot day after a stop & heat soak with AC on flat out it will crank up to full speed. I find the fan extremely obtrusive running flat out. The thing actually heterodynes producing a pulsating din. I don't like this.
My good man, one of the differences between us is that youíre an audiophile and Iím half deaf!
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Old 06-23-2010, 02:34 PM   #14
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My good man, one of the differences between us is that youíre an audiophile and Iím half deaf!
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Old 07-02-2010, 04:24 PM   #15
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Hey guys,
yesterday I was hitting the gas pedal (testing out the car since I got for about a month) and later I got this "Coolant Visit Shop" display on my screen. The fan won't stop running at max speed until engine turn off. I think the average temp is close to 90C when I am on freeway. My coolant level sensor is F---up since I have a full reservoir and same goes for the washer fluid. I think they are linked from reading a bunch of post on here. Please help!!!

On a side note: the engine used to vibrate at a stop when on "D" and my foot is on the break (stop vibrate immediately when I switch to neutral). I used the "fuel system cleaner" and this is my second tank with that stuff and I got a lot less vibration at stop light. But... can't really be sure since my F---ing fan is on and loud now.
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Old 07-09-2011, 02:04 PM   #16
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Any news on this "PDVNG MB", have you got this sorted out yet?
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Old 07-09-2011, 03:49 PM   #17
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If your engine controller does not get feedback from your fan controller it is designed to run the fan at full speed, and will signal the driver by putting the "Check Coolant Lamp" on. Once you diagnose your fan fault and repair it, the check coolant will go off.
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Old 10-13-2011, 12:44 PM   #18
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I have a E430 and I live in Sf Bay , i am noticing that my fan never stop working , from when I start the car in the morning and when i turn off the engine , any help is appreciated.
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Old 10-13-2011, 10:14 PM   #19
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Hi, If you check out the thread at this post you would see I have discovered the problem Radiator fan always on HIGH, regardless of weather or a/c, this is not normal.

You need to get your car up on DAS, it has a problem where it is not selecting the car's actual model. This can happen after a change of the electronic ignition steering lock or the battery been disconnected for a very long time i.e. a few months.

Once hooked up to DAS you need to select the menu for EZS Electronic Steering Lock (aka EIS) then select option 5 (CONTROL MODULE ADAPTATIONS) , Then whilst in CM adaptations select option 2 (READ/CHANGE CODING). In this it would show you options of vehicle model which would show UNKNOWN and LHS/RHS and also show UNKNOWN.
You must select W202 for C class or W203 as I guess you have an E class. Then also select what steering RHS for right hand drive, LHS for Left hand drive. this would then enable the ECU to recognise what setup for the car and control the fan correctly.

his can only be done by hooking the car up to a diagnosis machine that has DAS on it.
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02, ac, b122, benz, c240, constantly, fan, high, jaguar, mercedes, pressure, problems, radiator, refrigerant, running, sensor, troubleshoot


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