SLK 170 Compressor Clutch? P0806

[AdamG]

Hi,

I have been trying to get to the bottom of a problem with my slk's compressor clutch.

First I noticed a lack of power then read the codes with star and came up P0806 "compressor output stage open circuit"

I tried activating it with star and nothing happened.

I checked the connector and there is 12v on one pin and the other one is connected to pin 21 on the ecu and shows as a good connection with a multimeter.

I checked the resistance of the clutch: about 4 ohms.

I tested the clutch by quickly connecting the disconnected plug to 12v and it clicked and moved fine.

It looks as though the ECU is not grounding the clutch. Has anyone experienced this before? Could it be a dry joint or does the ecu control a seperate relay somewhere?

The wis suggests the clutch is directly controlled by the ECU but I'm never too sure about the wis circuit diagrams

Any suggestions greatly appreciated.

Cheers

Adam

 

[Alex Crow]

the power supply is thorugh the k40 relay module, you must also test the 12v supply and earth at the superhcarger plug when activating, often a k40 fault.

 

[Technics]

Hello,
I had the same difficulty withe the SLK 230K R170.
The main stage of the ECU was broken.
You need to replace one BUK101 MosFetTransistor in the ECU Unit.

Or you have to replace the whole ECU Unit and the EWS Unit, but this will make
a big hole in your wallet.
I have replaced the Transistor. erased the error code and all power came back to the engine. Fuel consumption was normalized and all error codes are gone and do not come up anymore.

Dieter

 

[AdamG]

Hello,
I had the same difficulty withe the SLK 230K R170.
The main stage of the ECU was broken.
You need to replace one BUK101 MosFetTransistor in the ECU Unit.

Or you have to replace the whole ECU Unit and the EWS Unit, but this will make
a big hole in your wallet.
I have replaced the Transistor. erased the error code and all power came back to the engine. Fuel consumption was normalized and all error codes are gone and do not come up anymore.

Dieter

Thanks for the reply Dieter.

Do you know where I can get hold of a BUK101-50dl as I have been looking everywhere?

I have tried several alternatives VNP28N04, VNP49N04 but both worked for a while then failed.

Thanks very much

Adam

 

[Alex Crow]

Is this one any use? http://www.ebay.co.uk/itm/BUK101-50...al_Components_Supplies_ET&hash=item256598ca93

 

[Bolide]

I have tried several alternatives VNP28N04, VNP49N04 but both worked for a while then failed.

Why are they failing? There may be a clue there - is there another fault you haven't found?

Nick Froome
www.w124.co.uk

 

[AdamG]

Is this one any use? http://www.ebay.co.uk/itm/BUK101-50...al_Components_Supplies_ET&hash=item256598ca93

Thanks for the link. I have actually bought one of those but have not tried it yet as I was not sure if it will work.

The original is BUK101-50DL the ebay one is .....50GL. I think they have a different current drain to signify a fault condition. These Topfets are quite clever and I wasn't sure whether the GL is compatible. I might give it a go though

The reason I went down the VNP28N04 route was someone on an Italian forum had used this mosfet for the same fault and it apparently worked.

Thanks

Adam

 

[AdamG]

Why are they failing? There may be a clue there - is there another fault you haven't found?

Nick Froome
www.w124.co.uk

Thanks for the suggestion.

I have looked at the clutch and it manually activates using a 12volt source. It moves nicely and looks to be ok. Also its resistance seemed ok I think 4 ohms. Also when I put the new mosfets in it woked perfectly for about a week and using star I could activate it no problem.

The problem for me is without getting an exact replacement for the mosfet I cannot be sure if the fault is the electronic component or the clutch.

Unfortunately replacement clutches are very expensive.

Also someone recently had a similar fault and it was the K40 relay but if that was faulty surely the new mosfets I installed would not of worked at all.

Thanks

Adam

 

[Technics]

MosFet BU101 DL50

This original Tranní has a safety circuit for the inductive load of the coil of the magnetic clutch.
Sorry but the working point of the BU101 50GL is different. Built for 6V, 7V, to 12V DC and a higher Main Voltage.
If you do not want temporary appearence of any mistakes in your ECU you need the original phillips type "BU101 50DL" with working point 3V,4V and 5V DC for a load of 12 V DC regular and maximum of 50V DC and 50A to have the ability for cutting the magnetic clutch.
The output of the CPU in the ECU is very weak and needs a protection circuit like the BU101 and the working point of the gate is used at 5V DC.

BU101 50DL is the usable Type.
I live in germany near Cologne.
Greetings
Dieter

 

[AdamG]

This original Tranní has a safety circuit for the inductive load of the coil of the magnetic clutch.
Sorry but the working point of the BU101 50GL is different. Built for 6V, 7V, to 12V DC and a higher Main Voltage.
If you do not want temporary appearence of any mistakes in your ECU you need the original phillips type "BU101 50DL" with working point 3V,4V and 5V DC for a load of 12 V DC regular and maximum of 50V DC and 50A to have the ability for cutting the magnetic clutch.
The output of the CPU in the ECU is very weak and needs a protection circuit like the BU101 and the working point of the gate is used at 5V DC.

BU101 50DL is the usable Type.
I live in germany near Cologne.
Greetings
Dieter

Thanks very much Dieter for your detailed answer.

You have confirmed what I feared, i.e. I need the obsolete BUK101 50DL.

Do you know where I can buy one?

Cheers

Adam

 

[Alex Crow]

Why not use whatever you can get that is closest to the correct tranny, and just use it to control a relay which can then switch the current.
That way you can isolate the inductance/impedance from that poor little semiconductor.

 

[AdamG]

Thanks Alex. That is a very good idea.

If Dieter knows where to find a replacement I'll give it one last try as it will keep the car factory and is easier.

It is surprising that it is not controlled by a relay. I think it was to save cost as these Topfets have a built in safety cut off so in theory I think if the clutch fails they shut down and send a fault signal to the processor.

I think the lead compliance rule finished them off

There are two more in the ecu controlling the O2 sensor (not sure on that).
Probably I could buy an old ecu and find one.

Cheers

Adam

 

[Alex Crow]

One of the others will probably be for the cam magnet, and possibly the other for the purge valve or O2 sensors.

Later M111 supercharged engines dispensed with the clutch and ran the 'kompressor' constantly with the recirculating air valve controlling boost and charger load.

 

[Technics]

Hello,
I have ordered mine at a chinese dealer.
The transistor cost value was 1 US$ but the shipping cost via Air mail was 25 US$ in an envelope.
You have to pay first and have to hope the dealer will send you the item.
And then you have to wait about 10 working-days to receive the MosFet Transistor.

MB service only changes the whole ECU for the cost of about 2000€ plus reprogramming all your real data to the new ECU. The key and transmitters have to be stored to the ECU else.
This is cruel and very expensive.
I think this is the wrong way to service the cusomers.

very sad.....
Dieter from germany...sorry for my english...

 

[AdamG]

Hello,
I have ordered mine at a chinese dealer.
The transistor cost value was 1 US$ but the shipping cost via Air mail was 25 US$ in an envelope.
You have to pay first and have to hope the dealer will send you the item.
And then you have to wait about 10 working-days to receive the MosFet Transistor.

MB service only changes the whole ECU for the cost of about 2000€ plus reprogramming all your real data to the new ECU. The key and transmitters have to be stored to the ECU else.
This is cruel and very expensive.
I think this is the wrong way to service the cusomers.

very sad.....
Dieter from germany...sorry for my english...

Thanks Dieter.

Your English is perfect......a lot better than my German:Oops:

It's ridiculous that the transistor is not available or at least a suitable alternative. There is no way I would buy a new ECU for the sake of a mosfet!

There must be quite a few people with this problem.

One final question. Do you mind me asking who your Chinese supplier is?

There are many people on China offering this chip but there is always the worry that they will not send it.

Cheers

Adam

 

[Technics]

BU101 50DL MosFetTransistor

Hello,
I had asked via the net for the Transistor at
"quote@utsource.net" .

Two days later I received an offer from the chinese dealer.
I had ordered via E-Mail and made a pre-paying.
All I had to do, wait and hope to receive the item.

It was successful and I am glad, the item was an original Phillips MosFet BU101-50DL made in Philippines and works fine. The only item was you have to mount it isolated to the case with a glimmer sheet and you can fix it with the original clamp.
In this ECU there are 5 other BU101-50DL used, so if you make an ordering I think it will be useful to order more items in one package.

Therefore I ordered more than one, because in europe the item is nowhere available.
If you have further questions you can ask via e-mail.
Dieter

 

[AdamG]

To update this thread.

I put in a request at utsource and the got a quote quickly.

I selected the slow shipping $4 from Singapore!

They have just arrived.

Thanks very much Dieter for the link. I'm now waiting on some ceramic insulator for them. I'll update when it is fitted.

Adam

 

[AdamG]

I tried the BUK101-DL and at first it worked but soon failed just like the other topfets

Strangely the failure mode is now for it to lock on. i.e the ecu is contantly earthing the clutch. Once the ignition is switched off it disengages.

So it looks as if the coil in the clutch is causing the topfet to blow. I can not see anything wrong with the pulley assembly though. The gap looks fine, no pieces hanging out and smooth operation.

The resistance reads 3.4 ohms.

Could this be a wiring fault between the ecu and clutch?

Has anyone seen the just the coil go bad but still work?

Thanks

Adam

 

[AdamG]

To update this thread again. I think I might of solved my supercharger problem.

I ordered another topfet from a different Chinese supplier and also added a little heat conductive paste. Originally there was no paste but I thought it was worth a go.

The supercharger has been running great for about 6 months now.

Hope this is of some help to anyone else having this problem.

Adam

 

[AdamG]

To hopefully give the final update to this thread.

Not long after the last update the clutch failed again. This time the failure mode resulted in an open circuit to the clutch and the topfet tested good.

So I took the clutched pulley off. The picture below is of the coil that sits inside the pulley that magnetically engages the clutch.



What had happened was the coil had shifted forward resulting in it rubbing on the pulley. This caused the outer shell of the coil to be worn away exposing the copper coils. Initilally it was prabably still creating a magnetic force but the part exposed coils may have caused an increased current draw blowing the topfet. Eventually the coil got worn to such an extent it resulted in an open circuit.