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Phillip H
Phillip H, ASE Certified Technician
Category: Mercedes
Satisfied Customers: 326
Experience:  Vehicle Technician at Richmond Motor Services
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I have a Mercedes V-Class reg CKZ4113 VIN -

Customer Question

I have a Mercedes V-Class reg CKZ4113 VIN - *****************. Model V280 Automatic
I have an issue with the cooling system.
Background info. The Rad and fan system was replaced with a donor from a diesel Van as rare to find one for a V280.
Issues...The Rad fan stays on all the time & the Climate control system is blowing hot air all the time.
work carried out.
I Have replaced the climate control module with New merc part. Have replaced the heater control module with new from Mercedes. Replaced various relays associated with cooling system.
Help required:
Does the ECU need reprogramming to talk with the fan management module?
Is there a technical diagram showing how cooling system works ( from central control switches. relays to aircon compressor?)
Any suggestions to make fan work through standard controls and not bypass?
Submitted: 10 days ago.
Category: Mercedes
Expert:  Virtual-mod replied 9 days ago.
Hello,

I've been working hard to find a Professional to assist you with your question, but sometimes finding the right Professional can take a little longer than expected.

I wonder whether you're ok with continuing to wait for an answer. If you are, please let me know and I will continue my search. If not, feel free to let me know and I will cancel this question for you.

Thank you!
Customer: replied 9 days ago.
I need an answer so happy to wait
Expert:  Phillip H replied 8 days ago.

Hiya

You should initially carry out a full diagnostic code read.  Once a code has been obtained a diagnostic path can be established.

The Radiator Fan and the Oil Cooler Fan are controlled by the Engine Coolant Blower Timer Control Module.  This is basically a large relay!  This is switched by the A/C Master Switch and also receives the reading from the Refrigerant Pressure Sensor.

The A/C module also receives a signal from the Engine Control Module so that when the Engine Temperature is high and requires the Fan for cooling it tells the A/C module that it needs the Fan on.

If the Fan is staying on all of the time I suspect that the Timer Module has failed and is allowing the fan to run all of the time.

I will send you some diagrams to allow you to check the voltage etc at the various points in the system.

Regards

Phillip

Expert:  Phillip H replied 8 days ago.

Hiya

Please find attached Wiring Diagrams for ECM and AC.  I will also paste these as PNG Files.

Regards

Phillip

Expert:  Phillip H replied 8 days ago.

AC Wiring Diagram

Expert:  Phillip H replied 8 days ago.

ECM Wiring Diagram

Customer: replied 8 days ago.
Sorry for being ignorant but you have sent 3 files and all 3 files are same. is that correct. Also for my own understanding do you have a drawing showing where the various components are. I have already spent a lot of money with technicians and they cant seem to find the components. so a simple diagram showing the various components that make up the cooling system including the air-conditioning.
In a nutshell i see 3 problems
1- rad fan staying on.
2- heater control valve is not working as its blowing hot air all the time
3- the aircon switch within the cabin does not activate the compressor when switch is activated. the light on the switch does not come on.
so basic overview of how this works in sequence with layout of the components . is that possible
Customer: replied 8 days ago.
the vehicle is at the garage so unable to use the phone option until tomorrow uk time
Expert:  Phillip H replied 8 days ago.

Hiya

You have a Word (.doc file) which gives you the Engine Control Module and the AC Wiring Diagrams which also lists what all of the components are.

I have also sent you both of the wiring diagrams as picture files as these are often easier to read from.

If the Air Conditioning is blowing hot all of the time you need to ensure that the system has enough gas.  If there is not enough gas then the Refrigerant Pressure Switch won't activate and therefore you won't get any cooling.  It could also be the Heater Flap Motor that is stuck in the hot position.  You would have to check if the Heater Flap is moving when the Temperature Control is operated.

If the gas level is ok and the Compressor still doesn't work then you need to check the fuse for the Compressor Clutch and it's associated relay.  There are also control fuses for the Control side of the system.  Check those as well.

If the 'Technicians' you have employed to carry out your diagnosis can't diagnose what is in effect a very basic system then they have no right to call themselves Vehicle Technicians!  I would be asking for your money back due to the lack of diagnosis and repair!

If you don't feel capable of completing the work your self I would suggest you take the vehicle to a Mercedes Dealer where they have Mercedes Trained Technicians who also have access to the latest Technical Data.

If you require specific location information for the parts listed in the diagrams then you would need to register for Mercedes B2B which is available here: Mercedes B2B. This is available with various subscriptions available from an hour through to a years access.

Regards

Phillip

Customer: replied 8 days ago.
The technician has checked all fuses. We have replaced climate control modules, regased the system. The compressor has been tested directly and works and you get cold air. However the system does not work through the controls. All relays relevant have been tested and a couple replaced. As there is no workshop manual, its difficult to confirm that everything has been tested. I will consider the b2b option and let you know tomorrow
Customer: replied 8 days ago.
The pressure switch was changed earlier today and still not working
Expert:  Phillip H replied 7 days ago.

Hiya

It's no good just playing parts darts and replacing things!  Could cost you a fortune!  Follow the wiring diagram and test each area eliminating as you go.  Start at either the beginning or the end and check for voltage at the various points and also the earths.  If you haven't got voltage or earth where there should be then carry out a continuity check of the wiring between the two end points to determine if there is a broken wire.

Regards

Phillip

Customer: replied 7 days ago.
Thanks. I have a auto electrician booked on monday and i have told him that i have the wiring disgrams. So i will inform you thereafter
Expert:  Phillip H replied 7 days ago.

Hiya

No problem.

Regards

Phillip

Customer: replied 1 day ago.
Hi Phil. Still working with the technician. How does the heater flap work? Is there an actuator or motor?
Where is it located? Thanks
Expert:  Phillip H replied 1 day ago.

Hiya

It will be an Electric Motor bolted to the side of the Heater Box.  If it has his and hers heating it will have a motor on each side of the heater box to control the independent zones.

Regards

Phillip