As promised Quackers, I'm back from my day out
And good it was too. a 300 mile round trip and 48mpg (from the 2.1TD)
Sorting out Activa handling is a very skilled job and unless your garage has a depth of experiece in the Activa system they will really struggle.
This is the way I would go about it:
Start up and allow full hydraulic pressure to be reached on normal height.
First check: Do "Citarobics" and ensure the height lever takes the car smoothly from normal to low, then up to high and back to normal. Stop if it sticks at any height setting, mindful that the Activa is slow to rise and fall and that the Activa rams can make it jerk suddenly at the front when going from low to high. It is essential both height correctors are working as they should. Check the front and rear fall and then rise again if you put weight on the ends of the car by sitting on the tailgate sill and the front slam panel with the bonnet up.
The next thing to do is check the hydractive electrovalves are doing as they should and switching between hard and soft mode correctly. You have two of these, one at the front down by the rad and one high up under the rear subframe. You should be able to hear them humming if you put your ear close. With the engine running, both front and rear should be relatively soft and easy enough to bounce up and down. Stop the engine, making sure all doors are shut, listen for the hum from the electrovalve whilst bouncing the front end of the car. It should still feel soft. After 30 seconds, you should hear a clunk from the hydractive electrovalve as it switches to hard mode and the suspension should stiffen considerably. the front should suddenly feel rock-hard.
Open and shut a door to put the suspension back into soft mode and repeat for the rear. Again, listen for the clunk after 30s and the suspension stiffening. It will not stiffen as markedly as the front but you will feel it stiffen.
If these tests fail, front or rear, you have a duff back-emf supressor diode in your electrovalve. A very common problem that strictly requires replacement of the failed electrovalve but can be cheaply worked around by use of Uncle Bucks magic box. It contains diodes that take the place of the failed ones.The hydractive elctrovalves can suffer corrosion on their plugs as they're in exposed positions.
Note that the hydractive electrovalves when off (no current flowing) set the suspension into hard mode. They switch on (operate) for soft mode. Hence why they switch off 30s after the car is stopped and doors closed to prevent battery drain. When driving, they spend most time switched on to set the suspension soft.
Checking the Activa electrovalve (which switches the Activa balancing sphere in and out as necessary) is not as easy to check. When the Activa electrovalve is off, the balancing sphere is in circuit and thus a less aggressive roll-correction regime is enforced. It switches on to bypass the Activa Balancing sphere for hard roll correction. There is one way to test this and that is to corner hard!!! Another way is to temporarily wire a small low-current LED across the Activa electrovale feed wire (a LED with a 330 ohm series resistor will do) and place it where you can see it whilst driving. Normally the LED will be off but if you throw it into a corner hard, it will initially light brightly for half a second and then glow dimly whilst it is on. The reason for the bright/dim is that a hefty current is applied for 500mS to operate the valve and then the current is reduced to a much lower "holding current" to just hold it on. In fact this holding current is a 1KHz square wave, the reason you can hear the electrovales humming when they are switched on (operated). If this did not happen the electrovalves would soon burn out. You can also put LEDs on the hyractive elctrovales too and see lots of pretty lights when driving!
Next, test the mechanical side of the roll correction system. Engine running, normal height and look behind each front wheel for the roll corrector linkage balljoints. Push and pull on one of them and the car should rock sideways as you transmit roll signals to the roll corrector along the linkages. Ensure you can rock the car off vertical in both directions doing this. Note that little movement of the linkages should be necessary to achieve this. I have found a problem where the car will rock one way but not the other. This is down to a partially seized roll corrrector, which is nothing more than a height corrector on its side but with instant response. They suffer in the same way as a normal height corrector if not kept well lubricated.
Jack and firmly support the car at the front and remove the front wheels. Inspect the roll corrector linkages from where they attach to the wishbones right across to the roll corrector itself. Any play at all in any part of the linkage will upset things, as will partial seizures in say, the linkage ball joints.
Check (or rather replace) the nylon pads the roll corrector linkages run through on the subframe. These wear badly, as do the linkage rods themselves where they pass through the pads. In in doubt replace. Both pads and rods are very cheap from Citroen and they do, despite looking quite benign, make a heck of a difference to how the Activa system responds. Also look for play at the ends of the linkages where thay attach to the roll corrector.
Finally, whilst you are under there looking at that lot, Identify the Yaw Sensor adjacent to the roll corrector. Pull off its plug and clean the terminals. Also, when feeling really brave, find the brake pressure sensor on the "K" junction under the LHM reservoir and clean its terminals as well.
That's it. That should bring the problem to light. I don't think I've missed anything but knowing me, I will have forgotten something...
Hope that gives you a start anyway.
so yes i went roundabout hunting and had much fun.... love that sensation of flat corning so much...
