W210 electric/auxiliary fan running erratically

[bob6600]

Right so after finally sorting the loss of water problem, today I went to Bham to see if the car could do a reasonable motorway run without leaking. All was well on the way. On the way home, i heard a loud noise which sounded like a hole in the exhaust as it got louder at higher revs.

When I got home, I investigated and found it to be the aux fan (the two at the front). It was spinning erratically and I noticed the following.

1. Engine idle - fan off
2. Rev at idle - fan spins very quickly and faster as the revs rise
3. When driving - fan gets faster (louder) as the revs rise and so when there is a gear change, it slows down a bit but picks up speed again.

Now I have never heard this before and it's obviously not working correctly. I will try and do a STAR session tomorrow and get some codes.

What I want to know is what controls this? Is it a separate sensor or the thermostat? Switch? I am tempted to pull the connector for now as it is not required and sounds like an aeroplane trying to take off lol.

As always, any help from the panel are appreciated.

 

[bob6600]

OK STAR session done, it showed up B1231 Coolant Temperature sensor B11/4 comes from engine control module. This to me is the sensor on the top of the radiator. I cleared the code and it didn't come back but the fault is there so may replace it anyway.



I also did a test/actuation on the aux fan and it does nothing. Confused

 

[Dec]

This yoke here has something to do with it… W210 RADIATOR FAN CONTROL MODULE - Google Search:


This lad has 3 videos on the subject…

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Dec

 

[bob6600]

Interesting. I wonder if this is due to no power to the fan?

 

[Dec]

The W210 control seems to be located in the same location as a W202, second picture below.

No idea if it is causing the fan fault but it I think it play some part in controlling the speed of the fan.


Dec

 

[bob6600]

Yes I would agree. I will be looking at this as well as the sensor/switch on the rad. Both are responsible for the functioning of the fan so hopefully will solve my problem. Thanks!

 

[bob6600]

Small update...

I disconnected the electric fan for a temp fix and IT STILL RUNS! Thinking I had gone mad I tried to troubleshoot and had an idea that there is air being forced towards the fan making it spin. Stupidly I eliminated the viscous fan but have realised that it is running a lot quicker than before and with engine speed. This causing enough air to make the aux fan spin. So, it looks like the viscous fan has failed!

 

[Dec]

So, you're completely cured then?

Dec

 

[bob6600]

So, you're completely cured then?

Dec

Not quite. I disconnected the aux fan and the connector came off in my hand! Wiring so old and brittle it snapped. The clue was the fan still running when the connector was off lol.

I now need to probably replace the viscous fan, bit of a pain.