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Pete
Pete, Mercedes Mechanic
Category: Mercedes
Satisfied Customers: 24659
Experience:  Over 15 years experience as a Mercedes dealer technician
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2001 Mercedes c240- 60k miles -radiator fan runs at gh speed

Customer Question

2001 Mercedes c240- 60k miles -radiator fan runs at high speed at start up the add coolant display is on on DISC and so is BAS indicator. Had a local guy look at it and he said that the ecu is sending a constant signal and he said ECU is NG however I did some forum searches and it seems that the ECU rarely is bad. Also everyone said that when it is it is not sending a signal is when and why the fan defaults to on immediately
Submitted: 5 months ago.
Category: Mercedes
Expert:  Pete replied 5 months ago.

Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay.

Did you have the fault codes checked at all using a scan tool that can plug in and communicate with all computers on your model here?

Let me know so we can continue,thanks Pete.

Customer: replied 5 months ago.
No
Expert:  Pete replied 5 months ago.

O.k.,is the add coolant and BAS lights all coming on at the same time here when this occurs and do they go off when the issue is not occuring?

Customer: replied 5 months ago.
On all the time
Customer: replied 5 months ago.
Issue never doesn't occur the radiator fan runs from the moment the car is started
Expert:  Pete replied 5 months ago.

O.k.,you will need to have the fault codes checked/read out to see what codes are set.This needs done with a scan tool that is fully compatible with your model here.Once this is done the codes can then be diagnosed to locate and repair this fault here.I have seen the ME (engine computer) fail and cause this issue here and in some cases can be all of the time or intermittently.It is rare to fail but it does occur.

The coolant level sensor may be at fault here and this may be causing the fan to run if the computer thinks the engine may start to run hot due to low coolant even though the coolant level is o.k.I have had to replace the coolant reservoir in the past before for the false low coolant message.I would start with having this checked to see if this resolves all of the issues here.

The BAS is a brake fault.The codes need checked/read out of the brake computer to help locate the cause for the BAS light and then repaired from there to correct this issue.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete

Customer: replied 5 months ago.
Thanks Pete I will delve into that on Saturday you might be onto something with the low coolant sensor I know the actual coolant level is good , how do I troubleshoot the sensor?
Expert:  Pete replied 5 months ago.

Your welcome.

Unfortunately I do not show a test procedure for this myself here.I think if you unplugged it it would still show low coolant level so I dont think this will help.I believe it is the dealers SDS machine plugged into your model is the diagnostics that help.it usually walks you through or the technician through testing this here to make sure it is the sensor at fault.

Let me know if you need anything else and feel free to rate my help here as this is how I receive credit for my time.

Thanks Pete

Customer: replied 5 months ago.
Ok so the sensor is in the reservoir and their is no way to check if it works? What style if sensor is it?
Expert:  Pete replied 5 months ago.

The sensor is in the reservoir as shown below.

https://www.dropbox.com/s/obeeg25xwqnzlct/cs-07-06.gif?dl=0

Unfortunately I do not show a manual way to test this sensor myself.Usually it is checked/tested with a dealers SDS machine or a compatible scan tool.

Let me know if you need anything else and feel free to rate my help here as this is how I receive credit for my time.

Thanks Pete

Customer: replied 5 months ago.
Will do
Expert:  Pete replied 5 months ago.

Thanks

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