radiator fan runs on maximum speed when engine is cold

[danello]

Hi all, recently bought a band new van vito w447 om654 and from the first day I noticed that the radiator fan when I start the car (-5 +5 degrees) the fan starts at maximum speed and stops after 10-15 miles or when the temperature exceeds 80- 85 degrees. I mention even if the air con or the internal fan is on or off it makes no difference, still on full blast. I took the van back to the dealer and they said: this is a characteristic of new engines and it is normal and in the diagnostic tests show no fault. does anyone have any idea if it really is normal and if not what could be the cause?

 

[ajlsl600]

Faulty sensor or lack of can signal puting fan in to full on. Possibly a default as opposed to full off and overheating the motor, tho if that the case I wud expect an eml . a scan with decent scanner shud prove this one way or another.

 

[grahamcol]

The dealer wants shooting!
Where on earth do they get this stupid nonsense from?

 

[BillyBoy]

Can't guarantee the Vito is the same, but I had an E Class with the OM654 engine and it never did this, note does my OM656, so I think the dealer is just trying to fob you off as they don't know the answer.

 

[Mr Greedy]

Get the car on a proper fault code/love data system and have a look at aircon pressure/pressure sensor faults/implausible/unusual live data on the HVAC system is another option.

If my memory serves, on my E class last year when I had a low pressure or pressure sensor fault, my car did this. I'm not sure it was otherwise apparent.

 

[danello]

Faulty sensor or lack of can signal puting fan in to full on. Possibly a default as opposed to full off and overheating the motor, tho if that the case I wud expect an eml . a scan with decent scanner shud prove this one way or another.

they said, they put the van on a diagnostic scanner and it has no faults. because I really don't believe them iI asked for a copy from scan to show me there is no faults on the van and I have received this:

 

[danello]

they put the van on a diagnostic scanner and it has no faults... because I really don't believe them iI asked for a copy from scan to show me there is no faults on the van and I have received this:

 

[ajlsl600]

Find the sensor, sender that triggers/controls the fan, disconnect it, wot happens? Suspect result is fan runs full speed as default? Just have scanner that can clear codes first. See what pops up when u disconect. And have a good look at all wiring n plugs between that and ecm

 

[LostKiwi]

Fan running all the time can be low A/C pressure. Quick simple check is to measure the pressure in the system.

 

[star]

I would say the opposite LK, low ac pressure wouldn’t require the fan to run at fast speed, on a car we would check the system pressure in live data, the pressure sensor sometimes fails giving a false high.

 

[Mr Greedy]

I've just trawled through my posts on 'the other side' to refresh my memory.

I had a leak in my condenser in summer 2021 and low/no gas, and my radiator fan would turn on (quite noticeably) within about 10 seconds of turning the engine on, even when the car was cold. Note, it wasn't an immediate start of the radiator fan.

My car is 2011 w212.
As per @star post above, I was easily able to look at the live data and see the pressure was down/zero.

I went for a Mahle premium condenser in the end, as Mahle is the original fit on my car. With Mahle, the cheaper conderser part number usually end with an 'S', and the premium one the part number ends in a 'P'. It was suggested the P version would be a much better fit and finish than the cheaper part.

My lower aircon pipe was aluminium corroded stuck to the bottom of the condenser, so I also had to order a new aircon pipe, which was a bit of a pain in terms of access, but only about £50 from MB Grangemouth.

 

[LostKiwi]

I would say the opposite LK, low ac pressure wouldn’t require the fan to run at fast speed, on a car we would check the system pressure in live data, the pressure sensor sometimes fails giving a false high.

On the r129 the fan ran on full speed with low pressure. Topped up and all good again.
Makes no sense I know but that's what happened!

 

[alexanderfoti]

I would say the opposite LK, low ac pressure wouldn’t require the fan to run at fast speed, on a car we would check the system pressure in live data, the pressure sensor sometimes fails giving a false high.

Yes it needs a good look through actual values for lots of modules. I have had wonky AC pressure readings give this, wrong coolant temp sensor readings. One that had an implausibly low gearbox oil temperature causing it!

To the op, its not going to log a fault code its going to need actual diagnosis!

 

[Botus]

no idea if related - I doubt it, but then it is a Mercedes - but to say NO faults is interesting - as photo 5 says

N62 Parktronic (PTS)

U015587 Communication with the instrument cluster has a malfunction. The message is missing