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Old 18-10-2010, 12:52 PM   #1
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Coolant Visit workshop message SOLVED

Hello everyone,
just wanted to share my experience,
had this message for a while, and it turned out to be broken wire that leads to the fan, the fan wasn't engaging, hence the temp could rise and the aircon wouldn't work properly

so if everyone has this message would advice to check the wires first

there is 4 pin connector that goes to the fan and its module
1 thick(red): +12V (always on)
2 thick(black): ground
3 thin (black with red stripe) : +12V (when ignition on)
4 thin (green with blue stripe): signal wire (low voltage PWM signal)

ps
the car is w203, also checked my friends w211, the wires looks the same
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Old 17-11-2010, 03:10 PM   #2
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I've just happened upon Madtek's useful post following a search to understand a problem that I have on my 2003 c200 CDI.

My car appears to be running in "limp" mode (poor acceleration and revs wont exceed 3K). When this first happened (some weeks ago now) it started to display the "Coolant - visit workshop" message.

I have checked the engine coolant level, and also the windscreen washer fluid level (which someone told me could be the cause because the w/w sensor and low engine coolant sensor were wired in series).

Both fluid levels seem OK, but should I be testing for correct operation of these sensors too? If so, can anyone suggest how I can best do this and advise where are they located as I can't even see them.

I have disconnected the electric fan plug described in Madtek's previous post. The plug has 4 wires as described except the "thick black wire" in my case is actually a thick brown one. I assume it's the same set-up.

I have put a meter across the wires and there is a permanent 12v supply across the thick red wire to ground (or the thick brown wire). There is also continuity between the thick brown wire and ground, which sounds correct.

There is no voltage at all across either of the thin wires and ground with the ignition turned off. This also sounds correct.

With the ignition turned on there is only 1.07 volts across the thin red/back wire and ground, which seems low. Shouldn't this be 12 volts or more? and does this automatically point to a damaged wire?

There is 0.34 to 0.4 volts across the blue/green wire and ground. Would this be correct and where does this wire go to?

All these wires disappear into the loom and then into a dark recess of an inaccessible corner of the wing. My recently purchased Haynes manual is very short of detail in the wiring diagram stakes and these do not appear at all, so I am not sure where they are subsequently connected to.

Would it be a good idea to run a continuity test across the fan plug end of the thin red/black wire and its starting point (wherever that may be) to test its integrity? And similarly with the blue/green one. Or is there a much simpler way to resolve this that I am overlooking, like maybe running a new ign fed live to the fan plug and if so where from?

Sorry theres loads of questions here but I'm hoping you more clued up types can help me put things right without me unnecessary unpicking looms and making things worse.

Ive been lurking on these threads for a couple of years now and have gleaned some invaluable advice on various things but I'm feeling a bit out of my depth on this one. Thanks in advance for any help you can offer!

Last edited by merc711; 17-11-2010 at 03:29 PM.
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Old 04-06-2013, 01:02 AM   #3
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My c200 2005 is giving the 'coolant visit workshop' message whenever I switch off my A/C. It has done this twice now, I drove it home yesterday without the A/C on and the alarm never came on. Driving to work, I monitored the engine temp, it went to about 80C. I switched on the A/C for about 30 seconds, then switched it off, and the message appeared again. Any ideas??
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Old 04-06-2013, 08:56 AM   #4
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On my car this was caused by a faulty engine fan control module. It comes with the fan assy.

You need to test if the fan is operating. Run the car to get the engine up to temp. Then stop leave engine running and the fan should start. If it doesn't. Then that is your issue.

Obviously you will have checked coolant level etc.
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Old 04-06-2013, 05:42 PM   #5
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Hi,
I posted earlier about my message 'Coolant visit workshop' I only get this code when I use the A/C. The code I am getting is P2518
Mercedes-Benz A/C Refrigerant Pressure Sensor "B" Circuit High

The car radiator fan is working normally.

How can I sort this??
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Old 04-06-2013, 05:44 PM   #6
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Anyone know where I can obtain a 'free' workshop manual for a C200, W203 ??
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Old 04-06-2013, 05:51 PM   #7
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Chiffy

Wehen I looked into this for my C240 I found three causes (most likely)

1) The fan control unit.

2) The engine temp sensor.

3) The coolant level sensor.

If short on funds then get it on a STAR with a good Indie. That will be cheaper then swapping parts in te hope that you hit the jackpot first swap.

FYI: A replacement fan with ECU from Dronsfields was about 90 and took me 10 minutes to replace.

Somebody else on here found a broken wire to the fan.
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Old 04-06-2013, 05:56 PM   #8
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Hi BruceMillar

Which fan are we referring to, the radiator fan or the A/C fan?
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Old 04-06-2013, 06:03 PM   #9
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Quote:
Originally Posted by Chiffy View Post
Hi BruceMillar

Which fan are we referring to, the radiator fan or the A/C fan?
Radiator fan..
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Old 04-06-2013, 06:06 PM   #10
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Can I ask, why is the fault code referring to the air conditioning? Can an independent garage do a star test?
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Old 04-06-2013, 06:08 PM   #11
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Also, I had the car running outside the house this morning and took it up to 100 degrees C, the radiator fan never cut in, what temperature should it cut in?? Sorry for so many questions!!
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Old 04-06-2013, 06:36 PM   #12
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I believe engine fan should it in about 90. The fan control at the bottom of the fan shroud is known for water ingress.
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Old 04-06-2013, 06:55 PM   #13
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Another question!! Are the fan and ECU one part? I have had a look and there is plenty of room to get the fan out, where are the fixings? I also had a look at the socket for the fan, the cables seem fixed in tight enough.
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Old 04-06-2013, 11:13 PM   #14
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I have been working on a this problem for a customer and he has taken it to four different mechanics here in the U.S and they were not able to diagnose the problem. His car is a 2005 SL55 AMG. I have done everything possible and I will list them so maybe it will help somebody.

Note: We swapped certain items from my personal car 2003 SL500.

Code:Electric suction for engine and air conditioning (open circuit)

1. The Electric suction fan was swapped with my car and that did not work.

2. The coolant temperature sensor was changed and that did not work.

3. We tried sending a signal with our STAR and that did not work.

4. We then spliced the signal wire from the fan and connected it directly to the ECU. The fan started acting up by going slower and faster every second. We knew from that moment that the ECU must be the problem.

Telling a customer the ECU is bad is probably one of the worst things you could tell them. So just to make sure I replicated the problem in my own car. I disconnected the ECU and took out connector 4 and disconnected pin 39 (this pin sends the signal to the fan) and guess what appears in my cluster: COOLANT VISIT WORKSHOP and the fan kicks on high mode.

The ECU has been sent out to be rebuilt and I will update when we get it back.
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