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Discussion Starter #1
I haven't lowered my roof in quite a while. I tried to on Sunday and nothing, no switch light, no noise, nothing. Yes, the retractable partition was pulled back and put into position. Fuse number 7 was blown, 5A, for Soft Top Control, Electronic Transmission Control, and Park/Reversing Lock.
I replaced the 5A fuse and it blew again.

Here are all of my current symptoms:
1. No Variable Roof operation, no lights on switch, and no noise of anything operating.
2. No power door lock operation with remote or dash button. The lights flash when using remote, but no door lock operation.
3. Rear window defroster button doesn't light up when pushed.

I have searched the forum but nothing relating to a "no light condition" on Roof Switch.

According to the VR Troubleshooting list, the Roof Switch (S84) gets power from terminal 15.

I suspect I have a defective N10-3 Multi-function Control Module. I'm going to have my indy friend perform a thorough scan to see if I can
narrow down the problem.

VR Troubleshooting-1.jpg
 

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From what I can tell (and this makes no sense to me - perhaps I'm not reading the diagram correctly) the only thing fuse 7 supplies is S84 Vario roof switch. The only active component in that switch is the light bulb that lights it up when you operate it. Does the fuse pop as soon as you turn the key on? Or only when you operate the roof switch? If the latter, have you spilled any drinks into the red switch?
 

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Discussion Starter #3
No, I haven't spilled anything into the red switch or shifter area. According to what I have read, fuse 7 also provides power to the Reverse and Parking Lock Solenoid Y66/1.
I just removed the N10-1 Module and discovered pin 58 was burned on the circuit board. I believe that this provides power to the roof switch.
Post #19 in the below thread refers to the Reverse and Parking Lock Solenoid in the fuse #7 circuit.

Photo of my N10-3 Module:

My N10-3 Module.jpg
 

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Disconnect the switch and see if the fuse blows still
+1 ............

Also, does the Fuse blow with N10/3 un plugged ??????????????

I'd say that there is a definite problem with that 🤣

HTH,
 

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N10/3 provides the ground side of the red light bulb - when N10/3 wants the light on, it closes the circuit. I'm not sure if it's using a relay or semiconductor, but either way - the only way it's getting too much current is if the bulb or wiring is shorted to +12v. My money is on the bulb (in the switch). But I'm still waiting on some answers from the OP....
 

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Although my money is still on the switch :) I finally found the correct wiring diagram that shows everything on fuse 7 - your fuse chart is correct per PE00.19-U-2720-RB, although there is still some confusion about exactly which mirrors participate in the auto-dimming. The above document shows it connected to H7 (the inside rearview mirror), but it shows it wired via X49/5 (which is the door connector). I would guess the auto-dimming affects at least two and perhaps three mirrors - do you know based on previous use? For process-of-elimination, you can disconnect the outside mirrors behind the access panel on the top-front corner of the door. Or just remove the mirrors and unplug the heater circuits (careful here - very easy to break).

To eliminate the shifter solenoid you'll have to unplug it at the solenoid.
 

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Auto dim operates on rear view and dr side mirror in my 172. I've read elsewhere that it is the same on 2001 r171 FWIW.
 

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Discussion Starter #10
N10/3 provides the ground side of the red light bulb - when N10/3 wants the light on, it closes the circuit. I'm not sure if it's using a relay or semiconductor, but either way - the only way it's getting too much current is if the bulb or wiring is shorted to +12v. My money is on the bulb (in the switch). But I'm still waiting on some answers from the OP....
Thanks efair,

I have a replacement N10-3 Module coming tomorrow, then I'll go to my indy next week to get a diagnostic scan to check for error codes. In the meantime, I'm thinking about removing the switch to check the light circuit.
 

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I would definitely remove the switch and test for a shorted bulb - ohms between pins 2 and 3 on the switch. It seems more likely to me that a failed switch has damaged your N10-3 module, rather than vice versa. It's a pain to get to that switch, and you need to be extraorindarly careful not to break the little plastic bits that hold the console down/together, and that hold the switch into the console. Don't go yanking on anything - and remove things carefully only after you're absolutely positive you've removed all the screws. Just take your time have a good light so you can see all the bits.
 

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Discussion Starter #12
Thanks efair,

I had to remove the console to replace the Lateral Acceleration Sensor in 2012. Yes, old plastic parts in MB's are always fragile.
 

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Discussion Starter #13
I would definitely remove the switch and test for a shorted bulb - ohms between pins 2 and 3 on the switch. It seems more likely to me that a failed switch has damaged your N10-3 module, rather than vice versa. It's a pain to get to that switch, and you need to be extraorindarly careful not to break the little plastic bits that hold the console down/together, and that hold the switch into the console. Don't go yanking on anything - and remove things carefully only after you're absolutely positive you've removed all the screws. Just take your time have a good light so you can see all the bits.
OK, so I removed the roof switch and measured across pins 2 & 3. It measures zero ohms when I connect my ohmmeter across pins 2 & 3, then climbs to 12 ohms within 3 seconds and stays there.

Any thoughts?

I have a replacement N10-3 Module, but I don't want to install it until I verify that the roof switch isn't defective.
 

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Discussion Starter #14
Here is a photo of a roof switch on eBay that shows the light works by applying battery and ground to pins 2 & 3.
If I were to try this, I would put a fuse in line on the positive side.
Let me know if this would be a good idea....or NOT.
570670
 

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Discussion Starter #15
OK, so I decided to use a 9v battery to check the roof switch light. I use to do this to check the idle control valve on the W201's. The light works with a 9v battery, so I don't think I have a roof switch (S84) issue.

570686
 

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Did it read 0 ohms for ~3 seconds? Or O/L for 3 seconds? If it's truly 0 ohms that seems like a bad switch. Try that same 9v experiment with a fuse inline and report back.
 

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Discussion Starter #17
Did it read 0 ohms for ~3 seconds? Or O/L for 3 seconds? If it's truly 0 ohms that seems like a bad switch. Try that same 9v experiment with a fuse inline and report back.
When I connect the switch to my ohmmeter, it reads 0 ohms, then creeps up in 2.5 ohm increments to 12.2 ohms in about 3 seconds.
I connected the switch to my car battery using a 5 amp. fuse inline, the light lit up and didn't blow the fuse.
 

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Discussion Starter #18
Installed N10-3 module, with everything connected the #7 5 amp fuse still blows.
With S84 Roof Switch unplugged, fuse #7 blows.
With N10-3 Module unplugged, fuse #7 does not blow.
With N10-3 unplugged, good fuse in #7, Batt. voltage at pin 2 Pink/Blk of Roof Switch socket.

Have to have diagnostic scan performed.
 

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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 [edit: N10-3] disconnected, measure ohms resistance between the [edit: non-hot ] side of fuse 7 and each and every single pin on the [edit: N10-3] 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.
 

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N10/3 ????

Yes, the whitey / yellowy dot is an LED as is the Red ..............



I am just about to change the White dot illum to green LED :D

@M4rCu5 will get that ;)

(I'm doing every Switch etc on the interior to match the Green Illum of my 200 mph Cluster ;)



HTH,
 
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