Front EV 1994 Mk2

[Lwdajo]

Hi All,

Does anyone know where I might obtain a front EV for a June 1994 Mk2 2.1TD RP6419.

The car's been away from me for a long time and mechanic is very sure this is the source of the hard suspension over speed bumps. A good EV has been tried and "cured" the problem, but prompted packed up.

Or, are they repairable?

I'd really appreciate any replies.

Thanks,
Lee

[xantia_v6]

See: https://frenchcarforum.co.uk/forum/view ... hp?t=31881 for a solution to restore the original performance.

And: https://frenchcarforum.co.uk/forum/view ... 81#p494381 for the modification to get better than original performance.

[xantia_v6]

I should also have said that a tired main pressure regulator will cause the front hydractive valve to close when going over bumps, as the original design relies on the system pressure being higher than the instantaneous pressure in the front suspension to hold the valve open.

[White Exec]

An account of fitting the late-Xantia regulators also appears here, after we had the lengthy discussion (which Mike links to above) about them on FCF...
viewtopic.php?f=7&t=8100&p=96913&hilit= ... tia#p96913.

Three years ago this was done on the 2.5 here, and it continues to provide a predictable and significantly improved ride. Others have reported similar, so well worth doing. Finding a pair of late-type regulators could be the most difficult bit - breakers' yards probably the best bet, unless someone here or on FCF has rescued some.

Whether you change your EVs/regulators or not, well worth adding the extra pair of diodes to the EV feed. A working diode is essential to correct and full operation of the EV solenoid, as well as protecting the suspension ECU from voltage spikes. The diodes embedded in the EV solenoid coils can fail, and it isn't practicable to access them.

XM EV Protection Diodes and LEDs v2.pdf

[Lwdajo]

Thanks both. The mechanical refurb is useful but the mechanic was trying to fit the twin LED mod for me when he says electrical damage was caused to the EV. I'm assuming he made some kind of mistake with the LED's wiring so I told him to stop trying to fit that.

What, electrically, might he have done to the EV? I understand there are diodes and a solenoid, and I have an e-crofting unit to replace the diodes, but might he have damaged the solenoid and is there anything else electrically in there?

Lee

[White Exec]

Oh dear, Lee, sorry to hear that.

The solenoid consists simply of a coil (d.c. resistance = approx 4.8R), with a small (reverse) diode across it, and embedded in it.
The brown body of the coil connector is marked + and -, moulded into the plastic.
Polarity must be observed, otherwise the diode will be destroyed.
Under no circumstances must 12v be directly applied to the solenoid, even with the correct polarity.

Under normal operation, the suspension ECU outputs 12v simultaneously to both EVs for just 0.5sec, which then falls to approx. 3v.
The "3v" which will show on a meter is actually a square-wave (pulse width modulation) at 1kHz, i.e. 12v with a roughly 25% duty-cycle.
The 0.5sec 12v is solenoid pull-in; the "3v" is solenoid hold-in, which is sufficient to keep the solenoid energised without excessive heating.

Although applying 12v directly, wrong polarity (perhaps by accident) is enough to immediately destroy the internal diode, the coil itself is unlikely to have become damaged, unless the 12v was left connected for a long time.

To test this, measure the d.c. resistance of the solenoid: if it shows up as 0R (dead short) with the meter applied in both directions, then the diode has failed short-circuit, and the solenoid coil (removable from the metal core/body) will have to be replaced.

If it shows the correct 4.8R in both directions then the diode is either working, or has blown, but open circuit. If this is the case, fitting an external diode (or an e-crofting kit . . . which is simply a pair of diodes, nothing more) will probably result in a properly working EV.

If the internal diode has blown (open-circuit), then the solenoid might close, but not operate correctly - it needs a working diode to work efficiently; an external one will suffice.

Important that all the above tests on the EV/solenoid are conducted with it disconnected (unplugged) from the suspension ECU.

It is possible that your mechanic has managed to damage the suspension ECU, but hopefully not. The EV(s) need checking out first, as above, though.

Note that connection of each of the additional (protection) diodes, AND the feed points for the tell-tale LEDs is made to the same two wires on the suspension ECU multiway connector - each of the two output wires supplying the EVs. Once the wires have been identified from the circuit diagram***, they can be checked by spearing the insulation with a needle, and checking that 12/"3v" appears there at the same time as (hopefully) the EVs are heard to click on. If that shows up correctly, those are the points to tap into for connection of diodes and LEDs.

*** Edit:
On suspension ECU, white 15-way connector:
Front EV feed is pin 1
Rear EV feed is pin 2
[source: circuit 580-2/20]

Unplug, and use a needle to confirm you've got the correct wires to those pins.

Let us know how you get on.

[Lwdajo]

Thanks Chris,

It's hard to know exactly what happened, as the car is far away from me, and communication is a bit limited.

I will pass on the electrical test info to the mechanic and see what comes back.

I have a spare suspension ECU, possibly working, if need be.

I believe I have the e-crofting connection details, but it would be great if you could post the circuit diagram for double-checking.

If the coil needs replacing, are they easy to obtain?

From what has been said, an EV appears to be repairable, both electrically and mechanically, which is slightly encouraging!

Regards,
Lee

[Lwdajo]

Thanks for the update on the pin layout.

[Lwdajo]

The e-crofting details I have are (which hopefully correspond to pin 1 and 2):

RP Specific Wiring Details for XM RP 6419

Connect the red wire from the Repair Kit to the following wire on the loom:

Wire Colour: Yellow
Colour Mark: Brown
Reference Fig: (none)

Connect the green wire from the Repair Kit to the following wire on the loom:

Wire Colour: Yellow
Colour Mark: Red
Reference Fig: (none)

Connect the black wire from the Repair Kit to the following wire on the loom (there are actually two identical wires on the wiring loom and you can connect to either of them):

Wire Colour: Blue
Colour Mark: (none)
Reference Fig: (none)

[White Exec]

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.