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Discussion Starter #21
I'm not convinced (nor is an electronics lecturer colleague) that the 14 will be heavy enough for the job. There's so much overload protection it can only take 14 amps.

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You are right and I had some concerns as well. The last thing I want to do is potentially damage the ECM by using a component that wasn't part of the circuit design.....a costly $$ mistake.

So earlier in the week I found a source for the BUK101-50DL (Ali Express).....sounds kind of hokey, I know. I ordered 5 ($14.00 including shipping) and they are currently on a slow boat "from" China. :D (chinaman)

They may not ever show up but I figured a cheap risk to take when the alternative is $450 to get the ECM refurbished.

Barchetta
 

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Discussion Starter #23
Just took delivery of 3 BUK101 - 50GL locally - identical to the DL but short circuit load protection max. is 20v, the DL is 35v but the switching rate is faster.

Electronics guru says the differences are minimal and should do the job. The "G" denotes a higher standard of component (read more expensive) and reckoned the manufacturers of the ECM use cost effective components to at least see it through the warranty period.

I'm going to take the car off the road during the holiday period and start fitting (not me, the components!). It's my first time doing this - wish me luck ;)
 

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Thanks for the update.....glad you were able to procure some.

My car is parked until spring so I'm ready to go (just waiting for some really cold weather :)). I'm still waiting for my BUK101-50DL's to get over here from China....if they ever do.

Good Luck with your replacements! Maybe I'll wait and see how you make out before I tackle it! If you are successful and it fixes our problem I'll be doing this.....:bowdown: More than likely I'll dive into it as soon as my BUK101's arrive.

I was going to remove each of the 3 transistors one at a time and test them with a multimeter as follows (they are NPN components):

The base-emitter (BE) junction should behave like a diode and conduct one way only.
The base-collector (BC) junction should behave like a diode and conduct one way only.
The collector-emitter (CE) should not conduct either way.

*** They usually will fail shorted from collector-emitter which explains why the return from the coil (F21) is always grounded.



Barchetta
 

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You could try that approach but since F21 is going to ground, you may find it has continuity to pins on several of the components.....I may be wrong though.

Disassembling the ECU is simple enough. The only pain is having to remove a bunch of spring loaded clip that secure the transisters to the aluminum housing of the ECU (for heat dissipation) before you can remove the board. You may not have to do that if you can identify the bad component and are able to replace it without seperating the pcb from the housing.

Also, there is a thin white strip attached to the back of each transistors to aid in thermal transfer to the housing so don't forget to swap it over to your new component.

I would also use an anti-static mat with a wrist strap as a precaution....unless you are working in an environment where the relative humidity is above 40%. The a/s mat w/wrist strap is cheaper than buying an %RH probe! :)

Hope this helps.
 

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Discussion Starter #27 (Edited)
I replaced the mosfet today - and......................................the s/c clutch is still on all the time! The mosfet had blown with by backearthing attempts but something else must also be earthing the clutch.

The single mosfet on the right side is the one connected to F21 (thanks c230 sport coup). It's connected to the centre pin (collector/drain?) I didn't replace the other 2 BUK 101s on the left side - I don't know what they control......................

How's the slow boat Barchetta?

 

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I got the correct mosfets from China and they are actually new components. I half suspected they would have been desoldered from used boards or something. I've been traveling for the past few weeks (currently in Copenhagen) so it may be a bit before I can give it a go.

Sorry to hear this didn't resolve your problem. Like you said, there may be other damage to the circuit. So you were able to confirm by testing that this mosfet was indeed bad?

I'll keep you posted! :):)
 

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Discussion Starter #29
Yes the mosfet was bad (I tested the new one for a comparison). The original mosfet(s) was manufactured in the Philippines for - not that far from China :)

The scratch marks were caused by clumsiness when removing the spring clips - I'll use circlip pliers next time :)

 

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Discussion Starter #30 (Edited)
OK, idiot of the day goes to..............................me!

Despite being warned by Barchetta about the thin white strip behind the mosfet, I couldn't get the old one off (it's ceramic and glued to the back of the mosfet), I assembled the new mosfet directly onto the aluminium heat assembly thinking that there was enough metal on the back of it to transfer heat - WRONG!.....................the ceramic is to electrically insulate the mosfet from the aluminium frame - I had succeeded it grounding out the new mosfet directly to earth, keeping the s/c clutch permanently engaged. The tab of the mosfet is also connected to the drain (collector) DUH!:stupid:

I slipped a piece of mica behind the mosfet to insulate it, reassembled it and the clutch is now disengaged. Now back to square one and find the real cause of the s/c not engaging or the M16/7 flap from closing. Time to look back at the K40 area again methinks........................every day is a learning day!
 

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Hi. I am dealing with the supercharger issue as well (it's constantly engaged). Thank you, Barchetta, for referring me here from SLKWorld. I am going to order some replacement transistors today. Keeping my fingers crossed!
 

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Discussion Starter #33
I replaced the mosfet and I'm now back where I started - s/c clutch not coming on. I messed around too much (see previous posts) and damaged the mosfet and it continuously earthed out.

I don't know where in the world you are delboy but I got BUK 101 GL which is a slightly higher spec mosfet from LittleDiode - Electronic Components Supplier - good service and reasonably priced. They seem pretty particular about where they source their parts.

The K40 relay is ok (tried another known one), the s/c clutch and wiring is ok so my next step is probably the throttle body or the crank position sensor. Just hoping it isn't an ECU fault :mad:

Does anybody know if the crank position sensor also doubles as the engine speed sensor? Subby? Otherwise I don't know what signal the CPS would give to activate the s/c clutch :confused:
 

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I'm in Los Angeles. With a very similar problem. P1236 and P0410 codes.
Magnetic clutch is working, always engaged and disengages when power disconnected to it. K40 is good, I replaced it and no change. The car drives pretty well, just cannot get rid of the codes.

I had the engine top de-carboned with the proper equipment, MotorVac.

Next I will replace the air check valve, it is corroded, and probably needs replacing anyway.

If that does not help, I will get a vacuum gauge and test the divertor valve
 

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Discussion Starter #35
I'd be interested to know what you find with the divertor, I guess you're talking about the M16/7?
Where are you going to carry out a vacuum check?
 

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BAD MOSFET!

Sorry it took so long for me to post an update, but I wanted to make sure I had actually fixed the problem. I replaced the MOSFET a while back, but was still having intermittent issues. I eventually opened up the ECU to take another look. My solder joint on pin 1 of the MOSFET (the gate) was bad. DUH! I re-soldered it and since then, it has worked flawlessly.

By the way, the original problem with the MOSFET was easily detectable without removing the ECU. Paranoid about damaging the ECU, I disconnected the car battery and was very mindful of static electricity. After disconnecting the SC clutch connector, I carefully measured resistance between the blue/green wire and a ground point in the engine compartment. Any reading other than infinite resistance likely points to a faulty MOSFET. (Reason: the blue/green wire leads to pin F21 of the ECU and connects directly to the MOSFET. It should only show continuity to ground when the car is running AND the ECU has engaged the SC clutch.)

Good luck to you all!
 

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Discussion Starter #37
Thanks for the update - did you only replace the lower right MOSFET? When I replaced that MOSFET the clutch immediately disengaged but I still have a problem having the s/c clutch engage properly - there's a missing signal somewhere. Next step is to try a known throttle body as there was an intermittant 1580 code flashed up on the codereader.

 

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Yes, dandywarhol, I replaced only the lower right MOSFET. (Many thanks to you, Barchetta, and C230 Sport Coupe for doing the groundwork.)

As a result of my poor solder job, I began to suspect that the clutch itself was going south. So I took it apart, expecting to see bad bearings and/or a damaged coil, but it was fine. That's when I decided to take another look inside the ECU, and discovered my bad solder joint.

By the way, I didn't trust myself to solder directly onto the circuit board, since it is 2-sided. So I snipped off the old MOSFET and soldered the new one to its legs. (From the picture you provided of your old MOSFET, it appears you may have done the same.) When I put the clips back on, I had to twist the new one a little, and I think that's when my solder joint weakened.

So, my case turned out to be relatively straightforward. But yours is definitely more puzzling. I agree that for some reason, the ECU may not be seeing the right conditions to engage the clutch. Since engine speed and throttle valve position are apparently the two things it looks at, I think you are right to suspect the throttle body.

At one point, I considered soldering a lead onto the gate of the MOSFET, and running it out of the ECU, so that I could monitor and see if it was getting the "ON" signal. I'd be tempted to do the same with yours, but it's probably not necessary, because we know the clutch WILL run, and as long as the new MOSFET and the soldering job are good, it SHOULD switch on under the right conditions.

I certainly hope you can find the problem. I wish I had some more ideas for you!
 

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Discussion Starter #39
I too had trouble getting the old mosfet off - I didn't want to put to much heat on the board. I got the outer two out of the circuit board ok but snipped the centre one and removed it separately. I soldered the new mosfet directly to the board but used a small crocodile clip onto the legs of the mosfet to take away the heat to the mosfet and it seems to be connected well to the circuit board. :)

There's a smashed 230 about 20 miles from me with working components - I just need to get the guy in the right mood and frame of mind to allow me to plunder it for parts.........I'm determined to get this ol' lady blowing :thumbsup: :D
 

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Sounds like you have more confidence in your soldering abilities than I do. Had I soldered it directly to the board, I surely would have burned or shorted something!

Getting access to that wrecked vehicle sounds like a great plan. A little parts swapping would probably get you to the bottom of it in no time!

All the best!
 
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