c5 mk1 h3+ strange hardness issues

[ml11ML]

Hi, (nothing to do with emissions systems this time Marc, sorry about that )

does anyone know if it's possible that the electrovalves for the center spheres can get half way or even fully stuck? Or could the hydractive ecu be doing funny things? It shows no fault in a lexia scan.

The issue I have is variable random ride hardness. By that I mean the car can change in suspension hardness between drives or even multiple times in a single drive. For example I can drive over 3 speed bumps in a row and it goes over each one in an entirely different way either fully stiff like with blown center spheres or rarely very soft (almost as soft as it once was all the time) or somewhere in between. There is also a random noticable difference in harshness over small sudden bumps and holes in the road. Tire pressures are all correct as on the door sticker (2.5bar) and the spheres are all good.

From reading around I understand that this used to happen with older systems but not on the h3+? Sadly I can't think of any other suspension component that could be causing variable hardness instead of just being fully hard like with blown spheres... Maybe the c5 is just now getting to the age where this is starting to happen.

I would also like to know if it's possible to force the hardness regulators (center sphere valves) to be in soft mode all the time either by connecting some wires to 12v or disconnecting them (not sure which triggers the soft mode/enables all of the spheres including the center one) in order to rule out the suspension ecu messing with me? I tried running the actuator test in lexia when parked and when driving and did not notice any significant changes. Not even sure when it was supposed to go hard or soft.

Thank you for any info or tips about this strange issue

[GiveMeABreak]

Even on the later more advanced systems deployed on the C6 and C5 X7, the valves can get stuck, but also remember the suspension strategy is also based on road conditions and driver input as to when and how long sport mode is maintained.

Here are the hydraulic blocks on this vehicle.

Reference	Designation
1	Hydractive sphere 3+
"a"	Towards the BHI
"b"	Towards the right hand suspension
"c"	Towards the reservoir return
2	Electrovalve slide valve
3	Hydraulic isolation slide valve
"d"	Towards the left hand suspension

G: Soft status

• When the electrovalve is no longer supplied, its slide valve moves under the supply pressure from the BHI
• The return to the hydraulic fluid reservoir is blocked. The pressure under the lower part of the hydraulic isolation slide valve is identical to that of the BHI
• The upper part of the hydraulic isolation slide valve is identical to that of the BHI. The hydraulic isolation slide valve moves under the spring action
• Flow of hydraulic fluid between the right hand and left hand suspension is possible. The hydractive sphere 3+ is no longer isolated from the suspension

H: Firm status

• When the electrovalve is supplied, its slide valve moves, frees the reservoir return and obstructs the hydraulic supply coming from the BHI
• The lower part of the hydraulic isolation slide valve is subjected to the pressure from the hydraulic fluid reservoir. The upper part of the slide valve is under pressure from the hydractive sphere 3+
• The pressure difference causes the hydraulic isolation slide valve to move and obstruct the passage of hydraulic fluid between the right hand suspension and the left hand suspension. The hydractive sphere 3+ is also isolated from the suspension

[ml11ML]

Thank you for the detailed reply. I tried different driving styles for example driving very gently with slow inputs as much as possible for a week and nothing really changed.

Do you maybe have some wiring layout images to help locate where the front and rear electrovalve wires end up (I assume in the engine bay at the pump)?

[GiveMeABreak]

The electrovalves are wired directly back to the suspension ECU contained within the Basic Hydraulic Interface (BHI).

If you want a diagram, post your VIN up here (Automasked on submission) as I'll need the exact options / systems fitted to your car.

[ml11ML]

Yes, that would help. VIN: VF7**************[VIN obfuscated, can be read by forum staff]

[GiveMeABreak]

Here you are:

Hardware
7740: Suspension electrohydraulic block
7747: Front suspension electrovalve
7748: Rear suspension electrovalve

Wiring

7758: Rear hydractive solenoid valve + power supply
7755: Rear hydractive electrovalve control

7756: Front hydractive solenoid valve + power supply
7754: Front hydractive electrovalve control