Suspension Query

Hi everyone ,i have just changed the front and rear center spheres.
You were all right !!! The difference when driving is remarkable!

Thanks again Best regards \Bob

Hi Noz,

Another interesting post. Can I just ask you about what you said here please? Does this mean that the eventual failure of the electrovalves is likely to cause damage to the suspension ecu and does this mean a replacement ecu would be required (presumably very expensive)? If so would it be advisable to replace the electovalves at set intervals (say when replacing spheres - possibly at 60k intervals)? Are the electrovalves expensive themselves and how easy or otherwise are they to replace?

Thanks

Roy

Hi Roy,

The answer to your queries is here:

http://club-xm.com/forum/index.php?showtopic=845

No, no, no, there's no need to replace electrovalves. As you will see from the above file they develop a small problem which makes the suspension run in hard mode all the time. The fault causes some damage in the ecu but it is not fatal. It is relatively easy to repair.

Cheers

noz

Accumulator pressure relief bolt is the 12mm
George

Hi Noz,

Wow - brilliant!

Many thanks

Roy

Possibly a far more brutal - but effective - way to insert the appropriate 1N4007 diodes, is as follows. Both unmarked ends are soldered to an earth (blue) cable and one each of the marked end of the diodes is soldered to ONE of the yellow cables which go to the softness controllers. The cables have had a small portion of the insulation removed and the bare wires of the diodes are sleeved to ensure no cross-connection.

I have described this as on a Series 2 set-up; it is essential that you make your own checks as to the correct identification of the cables before soldering, or be it upon youir own head!

As I have no idea how to insert a photo file on this site, I have sent a photo by email to noz who may wish to set it up for others to view.

Hi techmanagain,

Here's the photo you wanted posting. I reduced the size to make it quicker to download.

Just to be clear (sorry, techmanagain, I didn't quite understand your description but now with the photo it makes much more sense.) this suggested mod takes place just where the cables leave the Suspension ECU just before they head to the electrovalves. The advantage is that you don't have to open up the ECU casing to perform this mod. The orientation of the diodes (the end with the white/silver stripe) is very important to get correct. Get it wrong and you will short circuit the MOSFETS inside the ECU. Using a common blue cable for both electrovalves seems logical at the first pass, however, I don't know if the return current is also controlled by the MOSFET or only the supply current. If the MOSFET controls both then making the returns common will pass the current returning for both electrovalves through one MOSFET. Maybe someone who understands electronics could shed some light on whether this is a problem or not?

It would do no harm to arrange each diode so that they connect to one yellow and one blue cable each. That way you will be sure that only one electrovalves current will pass through each MOSFET.

Clearly there are a number of modifications which achieve the same end result. It then comes down to personal preference as to which one you feel more comforatable with or which one you feel most adept at carrying out.

Cheers

noz

ps
to add an attachment to a post, just write your post or reply as normal. Then click on the 'Browse' button located just below the horizontal row of smilies. A normal 'windows' dialogue box will appear inviting you to navigate to the location of the stored file you would like to post. Click on the desired file then click on the'Open' button (inaptly named but it is the standard dialogue box used for the open command also). You will be returned to the page where your post is waiting to be submitted. Click on the 'Submit post' or 'Add Reply' button as appropriate as you would do normally. Depending on the size of the file to be uploaded and the speed of your connection it may take several minutes to regain control of your browser. Please be patient. There's no progress bar so you can't tell how much has gone and how much there is to go.

This post has been edited by noz on May 04, 2006 07:51 pm

Hi noz,
Thank you for your alternative soldering point suggestion. I will re-arrange mine to your arrangement; it seems logical and safer.

Hi Noz,

I can't seem to find the photo you posted (for techmanagain). Could someone give me a pointer please.

Thanks

Roy

Hi Roy,

Don't know what happened there. Did I ever upload it or am I going completely senile?

Picture 3 posts up.

Cheers

noz

This post has been edited by noz on May 04, 2006 07:53 pm

Hi,

Have new corner and centre spheres fitted and there's a slight improvement on the previously hardish ride but I still don't feel it's right.

I've tested for the electrovalve clicks/buzz and I can definately hear the rear one - but I don't think the front one is working correctly (at least not all of the time). I've decided to add the additional 1N4007 diodes to see if this corrects matters.

I'm just about to have a go at techmanagain's (revised) modification myself but wanted to check something first:

Isn't it also important to connect between the correct blue and yellow pairs (ie so that the two wires being bridged belong to the same electrovalve) - or doesn't this matter?

Incidentally I had a go at opening a spare suspension ecu with a view to checking the MOSFETS's as well (and possibly doing the repairs inside the unit). The unit was (relatively) easy to open but the board itself seems to be held into the aluminium case by a powerful adhesive sealant applied to the inside flanges of the two connectors. An added complication is that the board is fixed inside the case with the components facing down - and therefore inaccessible until the board is removed completely. The only way I can see of removing it is by applying considerable force on the outside face of the two connectors until the adhesive seal is broken - but am afraid that this will surely damage the board/the connectors/me.

Has anyone tried doing this repair - and if so what's the approved method of removing this circuit board?

Many thanks

Roy

I removed the board from the casing to do the job -can't think of any other way if you want to stick the diodes on the board-. The foam-ish material around the board plugs, I broke it carefully and slowly just by sticking a flat srewdriver and making my way around each plug, using it as a lever -no problem with the board, it's strong and flexible enough-. Of course, remove the screws holding the board onto the casing before attacking the adhesive.
George

Hi Roy,

As george says its not to difficult to break the seal. Just start at a corner with a small screawdriver or the blade of a knife whilst keepin pressure on the front of the connector pushing backwards. You'll find it will come away no problem. The foam is not that sticky.

I maybe have not explained myself well enough. The purpose off adding the diode is for the long term protection of the MOSFETS. IT gives a path for the freewheel current to circulate without having to go through the MOSFET. If the MOSFET is already damaged because prolonged use with a bust diode i nthe electrovalve then adding the diode will not resurrect the MOSFET. IF its damaged, its damaged. You would add the diodes after replacing the MOSFETS as a precaution.

The original photo from techman showed the return wires commoned up. I suggested they needed to be separated into pairs and took it for granted that it was understood that meant pairs respective to each electrovalve rathr than mixed.

cheers

noz

Hi George / Noz,

Thanks for the tips on removing the board. I'll have a go with a little more confidence now.

Noz,

No - I think the information was great - thanks. If I've understood correctly there's a period of time when the diode in the electrovalve has failed and this will eventually lead to failure of the MOSFET. Can the failure of the diode alone (even if the MOSFET is still OK) cause the electrovalve to stick in hard mode? I suspect from reading "repairing_ecu.doc" from XM-L that this might be the case.

I have a problem with the front suspension - which seems hard but the back seems OK - and I can feel a difference (on the back only) when switching to sport mode.

I am going to add diodes for both electrovalves as per techmanagain's suggestion in the hope that both MOSFETs are OK. (I also understand that fitting an additional diode even if the original inside the electrovalve is working will do no harm and will protect the circuit if and when the one inside the electrovalve does fail. This would relate to the rear on my car.) If it turns out that this has no effect on the front then I'll have to replace the MOSFET too.

Replacement of the MOSFET looks straightforward but I'm less confident about the correct positioning of the diodes on the pcb - despite having studied the various photos. Perhaps once I remove the pcb itself it will become clearer! In any case - I'll already have made techmanagain's very practical (external) diode modification.

Thanks too for clarifying the correct "pairing up" of the earth wires for the diodes. I'll see if I can work out which is which - unless of course anyone already knows?

By the way - I followed the url link on your how to and found the additional photos and information. There's a mention on that web site of the (above mentioned) file "repairing_ecu.doc" from XM-L. I've attched a copy of that here (I hope that's OK) because it was uploaded to XM-L in a .RAR archive which isn't a very commonly used format for non GNU/Linux (Unix) operating systems.

Thanks

Roy

This post has been edited by mackay1 on June 02, 2006 05:07 am

Yes, you are right that you can still save the mosfet if the diode problem has not been going on for too long. If you take out the board you'll eventually get a visual impression of the state of the mosfet -less or more burnt surrounding board plastic-. If that is clearly very burnt (brownish instead of white), it means the mosfet has overheated too many times (because of the diode not doing its job) and then it might have died as well. But you are right in trying to add new diodes as a first attempt.

I soldered my diodes on the pcb but, as it was the first time in my life I soldered anything, I didn't do such a good job on one of the contacts, so, if u r in the same stage as me in...soldering, I think the external solution is far easier and safer.
George