Front EV 1994 Mk2

[xantia_v6]

From memory, the wires at pins 1 & 2 are both yellow, so for the red and green wires on the e-crofting kit.
The third wire (black) to a good Ground connection.

Check whether the 3rd wire goes to ground or +12V. I would check, but only have my phone here.

[White Exec]

Third wire definitely goes to Gnd. The additional diodes are strapped across the EV coils, so supply at one end, Gnd at the other.

[Lwdajo]

Yellow, yes, with (probably faded) brown or red markings - seems to concur.

[White Exec]

The blue lead(s) referred to are pins 8 & 15 on the same white connector. Both lead to Gnd.
If you haven't got it already, Gabor's Circuit Diagram Project here:
viewtopic.php?f=13&t=7592&start=60#p112051 (downloadable and printable PDF)
shows the EVs and ECU connections (pages 84-85).
Cable colours differ, although pin connections for these items are the same.

Also, if you've never done it, worth checking the Grounding points on the engine bay inner wings (half-a-dozen on one side, a couple on the other). These are eye-connectors 10mm-bolted to a welded square nut on the inner wings. Over time these can develop resistance. The square nuts were body-painted when the car was built (!), so best to undo each, clean up all the mating surfaces (scrape the paint from the nut face) and re-tighten. Protect with a dob of grease after tightening.

The are a couple more in the (RHD) driver's side footwell, behind the plastic panel by your right ankle, ahead of the A-post. Remove the panel for access.

[Dieselman]

Passing 12v into the electrovalve, in theory, can cause it to overheat, but in reality there are a number of XM driving round with exactly that modification, to either overcome faulty HA, or as a pre-emptive measure.
Likewise the diode won't be blown by the application of 12v. It is there as a polarity and back EMF protector, so has to stand significantly higher voltages than 12v.
If there is an electrical fault since attempts to install some LED's esuspect the output VN05 transistors in the ECU to be blown.

Your car hadnt recorded any electrical faults with the HA system when I checked it for you.

I would be fetching the car back from the specialist it is with as they don't have much HA experience.

[White Exec]

Likewise the diode won't be blown by the application of 12v. It is there as a polarity . . . protector . . .

Sorry, but that's not correct.
The internal diode is there for two purposes:
1 - To prevent (as you say) a back emf spike from damaging the output stage of the ECU, when the EVs switch off - in the same way that reverse-diodes are frequently added to relay coils, to protect the driver circuitry that operates them.
2 - To ensure proper clean and positive operation of the EV solenoid under PWM (hold-in) conditions.

It is NOT there to protect against wrong polarity connection. It would have to be in series with the coil to do this, not strapped across it.
If continuous 12v (correct polarity) is applied directly to the EV, the coil will overheat. It is not designed to dissipate something around 36W!
If continuous 12v (wrong polarity) is applied directly to the EV, the diode will offer no resistance to this, and will burn out.

The bodge practice of running these EVs with continuous 12v, in an attempt to keep the car in Soft mode, can't be recommended, and certainly not as a pre-emptive measure.

It is important, as you say, that fault-finding on Hydractive is in the hands of someone who knows the system well, and how it is designed to operate. General auto-electricians may well make incorrect assumptions about Hydractive circuitry, which can lead to added problems.

In this case, the correct connection and operation of the Electrovalve solenoids needs checking, before any attempt is made to connect them to the suspension ECU. Posts above details how this should be done, all of which can be carried out with the White ECU connector unplugged, so as not to risk damaging the ECU.

[Lwdajo]

Thanks again to you both.

So, to be clear as I can, on the events, mechanic tells me he replaced the front EV, in order to improve the ride over sudden changes in the road, e.g. potholes, and it vastly improved the ride.

He then attempted to fit two wires for the LED's to be fed through to the bulkhead, according to e-crofting instructions which gave the pin-out from the suspension ecu. I will never know exactly what he did, but he tells after this attempt, the suspension reverted back to poor performance over pot holes.

I have advised him to stop attempting to fit those LED's.

I could ask him to try the other suspension ECU that I have, along with the e-crofting device, with either of the two front EV's he has, though I originally tried this many moons ago with the original EV and I saw no improvement. If the ride did indeed improve after he fitted another front EV, this suggests to me that the old EV was either electrically or mechanically faulty.

I suppose he might have damaged the ECU when he tried to fit the LED wires.

I have a few family matters to deal with, which is partly why I haven't been able to spend the time on this, and hence having to try and find someone to do it. The mechanic does seem to be struggling though.

[White Exec]

I wouldn't risk damaging that spare ECU. You do need the help of either a good and careful auto-electrician, or someone familiar with Hydractive/XM. See that you are in Leicester - maybe someone here will know who might help.

Almost anything could have gone wrong with what is normally a very straightforward addition (the LEDs and e-crofting diodes) to the wiring. It now needs a methodical approach to nail the problem.

[Lwdajo]

I think Will recommended a place in Loughborough, perhaps he will jog my memory...

[Dieselman]

Jak and Dillip at Eurocars are Ex main-dealer Techs. I can't vouch for their electrical work, but there is nothing too special about the front HA electrovalve.
If the electrovalve has been damaged and is open circuit there will be a stored code (26 iirc).

I would look to get the car back from where it is currently.