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LOL, we've all done it, I just didn't know if you actually thought there could be a related fault somewhere else lol ;)
 

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Discussion Starter #23
Then I am out of sensible explanations and will probably just waste your time here. I don't think a scan is going to help. With the key off, fuse 7 removed, and N10-1 disconnected, measure ohms resistance between the [edit: non-hot ] side of fuse 7 and each and every single pin on the N10-1 harness... And report back any readings that aren't O/L or infinite.

BTW (and completely unrelated to your issue) it looks like the "variable illumination" of the roof switch is an LED.
With the N10-3 plugged in I get 2.8 ohms at the non hot side of fuse 7.
With the N10-3 unplugged I get 32 Meg ohms at the non hot side of fuse 7.
With the N10-3 unplugged and the self-dimming rear view mirror unplugged I get O/L at non hot side of fuse 7.

I'm still diagnosing the problem. Do you know the purpose of pin 58 on the N10-3 module, it gets voltage from fuse #7, but I can't find out what it does. I understand the Y66/1, the S84 roof switch, and the H7 rear view dimming mirror circuit, but not pin 58.

Thanks for your help.
570769


570768
 

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I've gotten totally confused between N10-3 and N10-1, sorry. According to my diagrams (starfinder) there is no N10-1. Only N10-3. And it's the roof module. My diagrams show nothing connected to pin 58.
 

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Discussion Starter #26
With the module plugged in, I get 2.8 ohms at the non-hot side of fuse # 7.
With the module plugged in and the cooling fan plug disconnected at the N10-3 module, I get
4.7 Mohms at the non-hot side of fuse #7.
 

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That's a great clue about the blower motor inside the apparatus box (the box where N10-3 and all the other modules live). You probably do have one. I don't know about the FL years, but it's been present on all pre-FL models I've ever seen. That blower motor is not documented anywhere in WIS, and they apparently fail quite frequently. In fact, I've never encountered an R170 in the wild with a working one. And I've never seen one where this blower caused problems on the N10-3. Look for a small "chimney", and look down in for the squirrel cage.

IIRC you can remove the pins for the blower motor from the big N10-3 connector without cutting anything.

Getting back to your diagnostics, you said:

With the N10-3 plugged in I get 2.8 ohms at the non hot side of fuse 7.
With the N10-3 unplugged I get 32 Meg ohms at the non hot side of fuse 7.
With the N10-3 unplugged and the self-dimming rear view mirror unplugged I get O/L at non hot side of fuse 7.
What were you measuring to? Chassis ground?
 

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Discussion Starter #29
I just powered everything up and fuse #7 did not blow with the module fan disconnected from the N10-3 module plug. I read 16 ohms across the fan motor leads.
Also, now my rear window defroster works.
I'm going to button things up and test the roof today.
Now to look for a fan motor replacement.
Thanks for all your help, much appreciated.

Why couldn't Mercedes tell us that fuse #7 that goes to pin 58 on the N10-3 Module also powers the module fan motor. I kept researching and finally found something about the module fan motor affecting pin #58.
 

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Discussion Starter #31
That's a great clue about the blower motor inside the apparatus box (the box where N10-3 and all the other modules live). You probably do have one. I don't know about the FL years, but it's been present on all pre-FL models I've ever seen. That blower motor is not documented anywhere in WIS, and they apparently fail quite frequently. In fact, I've never encountered an R170 in the wild with a working one. And I've never seen one where this blower caused problems on the N10-3. Look for a small "chimney", and look down in for the squirrel cage.

IIRC you can remove the pins for the blower motor from the big N10-3 connector without cutting anything.

Getting back to your diagnostics, you said:



What were you measuring to? Chassis ground?
Yes, I do have one, and yes, I was measuring to chassis ground. Luckily the fan motor (2 leads) has a separated connector that plugs into the N10-3 Module connector. There is a black release on the bottom side that lets you remove the fan plug.

570772
 

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I've replaced the motor in three of these blowers with brushless motors from amazon that were dirt cheap; I couldn't find anything "industrial grade". And I couldn't find an exact spec-for-spec replacement - I had to settle for "close enough". The comments you posted above (in white) make me wonder if brushless is a good idea. And as I said - I'd bet that 75% of all R170's are driving around just fine with non-functioning blowers.

Great job on the research.
 

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Discussion Starter #33
I've bought my 2001 SLK 230 new in 2000 and have never heard the module cooling fan run.
Thanks for the fan information. I'll probably call my indy/parts guy about a replacement.
 

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I've bought my 2001 SLK 230 new in 2000 and have never heard the module cooling fan run.
Thanks for the fan information. I'll probably call my indy/parts guy about a replacement.
Exactly how do you unplug the connector? I don鈥檛 see a black release anywhere, thanks.
 
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