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Discussion Starter #1
So I pulled my ECU on the weekend to replace the potentially bad S/C MOSFET.
However when I opened the ECU the inside did not look at all like I was expecting...
In the attached photo is anyone able to tell me which is the MOSFET for the S/C?
2661344
 

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1998 SLK 230
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See pics below...
 

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yep correct!
 

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see below
 

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Discussion Starter #7
So I pulled my ECU out again and replaced the MOSFET as identified by Subby_

Not sure if it worked or not.... IF the MOSFET has fixed the supercharger, how noticeable would it be?

Previously when I have tested the acceleration the car seemed to struggle to get to 140 km/hr. It seems now that I got to 130 (before I had to slow down) and the car was still accelerating and quite keen to go beyond the 140 as previously attained. But the power wasn't.... impressive. I didn't go WOOOOAH . Should I? Or is the power subtle?

Confused.
 

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Discussion Starter #8
Just watched some stock R170 acceleration tests on YT (manual admittedly) and I'm getting nothing lie they are.

S/C ain't working methinks.
 

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to test (keep the bonnet up so you can hear it or get someone to look);

with the car in N or P, bring the revs up slowly to 2-2500rpm you will here it click and start to engage from ~2,000rpm onwards
with the car in D it will be off at idle and turn on just above idle like 900rpm or so

if your car is stock and auto your 0-100 will be about 7.4 sec. 7.2 sec is for post facelift. those are the ballpark times, basically low 7 sec.
 
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this vid is from a forum member... this is exactly what it should look like

 

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Discussion Starter #11
Yes I think that's really the only way to be sure. My car is so loud though that I can't really do it at home.... I'll have to wait until I am out somewhere ;-)
 

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Discussion Starter #12
It's been raining today and I thought I'd turn off ASR and take advantage of it....

I noticed today especially that when my car is cold it seems to be extra spritely....

I don't normally drive to work, but did today due to the rain. Where I park leads up a tallish hill, and I turned up that hill it seemed to want to pull like a schoolboy. I was pleasantly surprised.

So to my mind 1 of 3 things is happening.
1) The S/C does work when cold, which I believe could be the case in certain models. But maybe not working when the engine has warmed up?
2) Turning off the ASR has some how sparked more like into the motor?
3) I'm imagining it all...

Subby_, your thoughts?
 

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what could be also going on is that the electromagnetic clutch itself has a short. unplug it and measure the resistance across the the coil it should be 2ohm or something like that from memory.

when mine failed i had to change the MOSFET & s/c magnetic clutch as my coil shorted in it (i guess thats what caused the MOSFET to blow). mine use to do the same from cold start the s/c would engage and then not engage after that.

ASR shouldn't have an impact unless its breaking traction it will cut throttle.

measure the resistance of the coil and post back (unplug at s/c)
 

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part no for new clutch is A1110970128 but its hard to find... if confirmed its gone, just get a whole second hand s/c unit (thats what i did) and strip it for parts. its more cost effective.
 

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Discussion Starter #15

part no for new clutch is A1110970128 but its hard to find... if confirmed its gone, just get a whole second hand s/c unit (thats what i did) and strip it for parts. its more cost effective.
Sweet thanks. I'll try and get to that this coming weekend.
Wrecked SLK's are scarcer than hen's teeth here so it could be a long wait if I need to replace the s/c.....
 

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same here in Aus. I get all my salvage stuff on eBay with most of it either coming from USA or UK.
 
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