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· *Premium Member
2001 SLK200K/2001 SLK320
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3,906 Posts
Might be piece of the puzzle, might be nothing...anyway the controller of that fan needs power supply too. I am not in search mood, to dig into the wirings and figure out is it (indirectly) coming from the k40 or ...need beer, food and shower. Probably more beer...
There you go ..
Rectangle Slope Font Parallel Pattern


Further testing required but atm I'm not convinced that it is the K40 :unsure:
 

· *Premium Member
2001 SLK200K/2001 SLK320
Joined
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3,906 Posts
Looks like you are correct!
Hot all time, sounds like non stop, so ...there is a potentially busted fuse (resistor, capacitor......) inside the controller that is sending 100% rpms right NOW signal...
Yes, the fact that the fan runs with Ign. OFF (always thought that was more of a secondary K40 symptom rather than a primary w/Ign. ON unless I'm missing something?) and the car is showing no other dodgy K40 symptoms, does kinda lead away from the K40 even though that particular one does look a bit suspect in one or two places :unsure: 🤷‍♂️
 

· *Premium Member
2001 SLK200K/2001 SLK320
Joined
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3,906 Posts
That light is on because there has been a power interrupt (disconnected battery) - you need to reset the Steering Angle Sensor by turning the Steering Wheel ~ Left Full Lock, Right Full Lock and Return To Centre ~ light should then extinguish

Personally, I'd disconnect the fan control module and leave the K40 alone for now
 

· *Premium Member
2001 SLK200K/2001 SLK320
Joined
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3,906 Posts
Is the fan control module the block in the bottom right I hover over in the video?

Will the car be safe to drive if the module's disconnected?
Yes that
I've just disconnected mine by squeezing the tabs together and pulling the connector off, it took me 10 seconds but if I was planning on leaving it like that I'd probs put it in a bag or something to protect it, or go looking for the 50A fuse
Circuit component Hardware programmer Electronic component Electronic engineering Computer hardware


As I see it...
The fan won't come on, but late-November UK it won't be needed anyway - probably/maybe 🙃
The fan is designed to come on at 100c so unless you have a severe coolant loss or we get a sudden heatwave and you happen to find yourself sat in heavy traffic for an extended period it should be fine as a (very) short-term solution.

Maybe there's an issue with the controller, maybe there's an issue with the wiring, maybe there's an issue with the K40 after all but at least you won't be draining the battery every time you connect it up.
 

· *Premium Member
2001 SLK200K/2001 SLK320
Joined
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3,906 Posts
Ok - I've put the relay unit back and unplugged the fan module. As you say, I can now connect the battery, the engine starts fine, but obviously the fan isn't working. I plugged the module back in and it immediately starts again.

I looked again at the coolant temperature sensor replacement and I must've been looking at something else last time cause it was incredibly simple - I've replaced that sensor now. No change, but then it wasn't likely to be a sensor problem if it happens before the engine is started, right? Or am I misunderstanding how these things work?
Nope, you're reading that exactly the same as I am. Gotta be something amiss with either the control module or the wiring
 

· *Premium Member
2001 SLK200K/2001 SLK320
Joined
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3,906 Posts
Ahhhhhhhhhhhhhh ...........................

Wait a doggone cotton picking minute ............................

Now it makes sense .............................

'Dave light-bulb moment' ............................

It (absolutely, almost certainly, pretty much definitely, 99.9 % bloody surely) has to be the Fan Controller Unit itself that has shattered it's pantaloons ;)
Why ?

Because that is the only part of the equation that is fed from a permanent Battery +

Get a good used one and plug and play (y)
@benfrew says it's working now, or rather, it's not causing the fan to come on anymore when it's connected :unsure:
Needs a session on SDS to make sure that the fan will run as and when it's required :p


I want to know where the coolant has gone now though and maybe the clue is here in OP's intro? :-
There's also a problem where there's too much moisture in the cabin (water ingress from corrosion?), causing the windscreen to mist really quickly and thickly. In cold weather the condensation frosts on the inside of the windscreen. I don't have A/C on this model, and the hot blower only shifts it slowly and at full power, so it makes driving in winter a bit sketchy!
Usually we'd say the drains are blocked, change the cabin filter etc. ..
 

· *Premium Member
2001 SLK200K/2001 SLK320
Joined
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3,906 Posts
Not being funny just asking, coolant leak is or is not a MOT failure?
Knowing issue with pipe, expansion tank, etc....is not making the car "dangerous" is it?
Depends how bad it is, quote from RAC:
Coolant leak
You might be surprised to learn that leaks of fluids such as engine coolant and screen wash aren’t considered reasons for failure.
According to DVSA guidelines, a vehicle will only fail the MOT if a fluid leak creates a pool on the floor within five minutes that’s more than 75mm in diameter, or if there are many leaks which collectively leak fluid at the same rate.
 

· *Premium Member
2001 SLK200K/2001 SLK320
Joined
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3,906 Posts
I picked it up and it drove home beautifully. Such a shame, but it's getting picked up for scrap tomorrow. They're giving me 410 for it so all in all I shouldn't be too disheartened. If I had a garage to put it in I'd keep it and learn to fix it as a project, but alas....

Thanks again for all your help. If I ever get another SLK, I'm sure I'll be back here!
Which scrap yard is offering £410 collected? Seems a fair price
 

· *Premium Member
2001 SLK200K/2001 SLK320
Joined
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3,906 Posts
In actual fact, we only have one garages word that it is H/G, if I were OP I'd buy an inexpensive sniffer tool and double check that diagnosis, if H/G is OK, next step is to buy a metre of heater hose and some Jubillees to bypass the Heater Matrix to see if the leak stops ;) Like he has said it is running OK ;)
Im glad you said that, as it does seem odd that it's running so well, whilst losing so much coolant :unsure:

1ltr+ in an hr that's presumably dumping into one or two cylinders and it's still pulling like a train? hmm :unsure:

Could be very mild Head Gasket, which is where they most likely gained their conclusion from .. AND the Heater Matrix..

£410's pretty good though, all things considered
 
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