Hydractive Suspension Ecu, Diagnosis and Repair

Hi all,

Thought I'd put together a small 'How-To' for the repair of Hydractive suspension ECU's due to failing diodes in the electrovalves. Before anyone else points it out I'll put my hand up and admit I'm no electronics engineer. If anyone reading this thinks I've made a fool of myself then please let me know which text is wrong and suggestions for corrected text. I'll gladly update the document accordingly.

Hope this helps those suffering from the type of suspension experienced in the cars of lesser mortals (owners of non-hydropneumatic cars).

All comments welcome.

Cheers

noz

Very good manual -although, Hydractive 1 also have two hydractive spheres but only one electrovalve-.

BTW, another cause of the hydractive valve closing and making the system going to hard mode, can be too low system pressure. If the pressure regulator max pressure is lower than specifed (170+-5 bar) it is possible that the valve that actually cuts out the middle sphere (not the electrovalve) to be instantly pushed to the closed position by a capable hydraulic shock produced from a bump of the road. This has been reported by a few people. So although your electrovalve(s) might be perfectly working, you might be getting hard reactions from your car. Check the suspension's hydraulic schema to understand how this undesirable phenomenon works out.

George

Hi all,

Apparently the file above can't be printed. Try this one instead.

Cheers

noz

I split my Susp ECU tonight to replace the VN05N's and fit the diodes.

Ahh....it's a H5 ECU and is very different to the pictures so far posted.

Has anyone figured out where to put the diodes on the H5 board?

The VN05N's are orientated 180 degrees different to the previous versions, i.e- the heatsinks face into the centre of the board and the legs are on the extreme edge of the board. There is a square area of un-etched copper left on the board that the VN05N's are stuck to - must be some limited heatsinking.

I also have some discolouration to one of the blobs of gloop that is holding one of the devices to the board, so I guess we've had some overheating going on. The other one looks fine.

Looks like I'll be just replacing the VN05N's and putting the diodes into the wiring, unless anyone can post a piccie of the correct diode placement?

Pic 1, Pic 2

This post has been edited by wirdy on February 08, 2007 12:06 am

Hi wirdy.

My board is different as well to the piccies. I'll be putting my diodes into the wiring loom.

The really sad thing is that I've worked in electronics for the last 22 years and given the patience / time I could easily work out the circuit diagram and where to put the diodes.

But I find life is too short to do things like that these days

A course that many will be following, I expect, now that Roy Mavckay has provided such a quick and easy fix for that job - just a pair of pliers needed - and 20 mins to spare to fit it. Contact Roy on roy.mackay@e-crofting.com for more info.

Part of the problem (for me) is that my XM is the only one I've ever driven, so my experience of how how they should feel is very limited. Having said that, this is a very interesting thread................. Jim.

That has been my problem too Jim.

I have confirmed most of my reasoning now, by having the susp ECU completely removed and driving the car to work - there is no difference to the hard front suspension, however the rear is a tiny bit harder. This is all with electrovalves that were buzzing quite happily prior to removing the ECU.

I may need to look into this system pressure thing if the repaired ECU and new diodes make no difference to the ride quality.

I must get the spheres changed on my other XM, they're rock hard, only then will I have some true comparison!

I can only relate to previous Cits I have owned i.e. DS, CX, BX. With the suspension in good condition and all spheres doing their job. At rest with handbrake on and engine on tickover it was possible to push any corner of the car down a ridiculous amount (6-8 inches?) with very little effort at all. I have no reason to believe my XM will be any different when the suspension is sorted. I have to do the diodes and mosfets and probably replace most of the spheres as well.

Driving a Citroen with well sorted suspension on an undulating A road at 50-55mph is an almost out of world experience . It really is like that fabled magic carpet ride. I have never experienced anything else like it. At the moment with my ecu out and commuting to work along the rutted tracks of the Black Country on fast failing spheres is like being condemned to a living hell! I'm in total dread of seeing a strut top come leaping through the bonnet due to the excessive strain on the structure.

Hi All

My impression is that you get quite a bit less of a "corner bounce" from the back of an estate than you do from a car. Is this in part due to the larger cylinders and higher tyre pressure?

Regards

XMexc

Hi guys,

Could we take the discussion to the hydraulic section and leave the self help section for files and tips?

Cheers

noz

Between pin 5 (white striped end of diode, the cathode(K)) and any ground area of the pcb.

See photos and description (giving correct pin numbers) in the thread "Suspension Ecu?, Where?" in the Hydraulic section.

Relates to Hydractive II ECU's fitted to all XM's from RP 6383 onwards irrespective of ECU version.

Roy

This post has been edited by mackay1 on September 16, 2007 09:28 am