Xantia 1994 hydractive II problems

[inooid]

Hi all,

I am currently diagnosing a problem with the Hydractive II suspension on my Xantia from 1994 (a pre facelift model, with under 60k miles). It's stuck in hard suspension. I've connected the Lexia with someone from the Dutch Citroen forum and it gave me a "Permanent Fault: Front electrovalve" fault (the rest of the errors were just older errors and did not stay when we cleaned them up).



My local garage replaced the front electrovalve with an used model from one of his donor Xantia cars, but the computer still gives it problems. The original electrovalve connector (that connects the electrovalve with the hydractive ECU) contained a bit of LHM oil as if somehow there was LHM leaking into the actual connection to the ECU.

I've checked the state of the actual hydractive ECU VN05N solid state relays and they show some signs of excessive heat, but don't look melted or completely destroyed (I've seen some pictures on other threads that looks waaay worse ). Solder joints look perfectly fine still and apart from some darker parts underneath the solid state relays I don't see anything unusual.



I am planning on driving to a garage somewhere next week that still has a spare hydractive ECU to figure out if it's the ECU itself that has a broken solid state relay, just to rule out the ECU itself.

Today I did notice however that the new electrovalve's connector (that connects the electrovalve to the hydractive ECU) contained a bit of liquid again (probably LHM and it looks similar to what the old electrovalve looked like, see photo) and I also noticed some LHM sweating at the pipe that leads back to the reservoir. In the technical training diagrams I don't see any connection between the LHM circuit and the connector, so unlikely that it's an internal leak within the electrovalve that caused the liquid inside the connector. I just don't fully understand what it could be.





I've cleaned the reservoir pipe completely and we'll see if the LHM comes back after some time. Also I've tried cleaning up the connector from all the liquid to see if this changes over time as well.

I wonder what you all think of the LHM sweating that's happening in this reservoir pipe, since it might be time to find a replacement for that as well (probably the rubber that's just getting old). Perhaps anyone here has a bit more of an idea of what it could possibly be. I will keep this thread updated with the information I got from when I get my hands on a new hydractive ECU to test if that resolves the issue. A side question: "Does anyone have an old Lexia cable that they want to sell that still works with these older mark I xantia's"? I've heard on the Dutch forum that the Ebay clones are a bit 50/50 in terms of whether the connector actually fits or not. If anyone has a good link or wants to get rid of their adapter, let me know!

Thanks!
Boyd

[white exec]

Hi Boyd,

The suspension ECU may well be ok, especially as it has no signs of burning, and is also fitted (presumably correctly) with the additional protection diodes.

When the IGN is switched on, the suspension light on the dash should illuminate briefly while the ECU runs a diagnostic on itself, and on each of the connected devices (sensors, electrovalves). The check on the EVs is limited to a resistance/continuity one - basically just checking that the EV is there, and not shorted or of unexpected resistance.

If a fault anywhere is found, the suspension light will either blink or remain on. (The only other time it will remain on is when Sport is selected.) You'll know all this, I guess!

Suggest you hook up an oscilloscope to each of the EV + lines, and see what is being delivered there.
This is what our Hydractive 2 looks like:

As per training document...
- full system voltage for 0.5sec (solenoid pull-in), around 3A taken
- then "3v" - which is actually 25% duty cycle at 1000Hz - (solenoid hold-in).

The square hold-in waveform should look reasonably clean, without spikes or overshoots, if the diodes (either the ones embedded in the EV coils, or the additional ones) are working correctly. If a diode is not present or faulty, the hold-in will be weak.

To check whether the EV is operating hydraulically correctly, connect a small clear tube to the fluid return snout (the one which is leaking). Each time the solenoid operates, a very small amount of LHM should be expelled (for return to the reservoir). The system also needs not to have trapped air in it, as this will be compressible, and allow road shocks to produce intermittent unwanted Firm operation.

You could be right about the leak just being a tired hose. Check that the return hose/path is not blocked, by blowing down the hose to make sure there is no undue resistance to flow back to the reservoir. Not helped on the Xantia front by having the EV pointing upwards!!!! (They're both horizontal on the XM.)

The suspension ECU's are amazingly reliable, considering everything. Check all the other bits first, including the two ECU multiway connects, AND the grounding points in the engine compartment (disconnect and clean back to bright metal; protect with grease only after tightening up again).

Wondering also what brought up all the other logged faults (which you say are now cleared)? Was something unplugged temporarily, maybe? A grounding fault could have brought up multiple faults.

Let us know how you get on.
Hope helpful.

[inooid]

Thanks Chris! I think you're confusing the Xantia with the XM, since my Xantia (and as far as I know no Xantia's) has no suspension light on the dash, it only has the light on the button for turning on or off the "sport" mode (honestly wish it did have the light on the dash, it would be so insightful!!).

As for the oscilloscope, I don't have one so I'll need to check if the garage can check this for me or look around and see if I can find someone that has it. I suppose this is pretty much the only way to really rule out if it's a ground problem? The diodes were added after we've first opened the ECU. It's something the Dutch forums recommend after our German neighbours presented on a forum. It's just another way of doing it.

As for the potential leak in the hose, can I just take off the hose, take a different (perhaps transparent one) and connect it back into the reservoir myself? Do I need to depressurize the system? I am still learning every day about how the system works. Do you happen to know the diameter size?

As for the logged faults, last year the battery was replaced so that could be it, but also the another forum member (from the Dutch forum) mentioned that these specific errors happen quite frequently for example when the steering position is not in the middle when the engine starts it calibrates wrong and logs the fault. He recommended just to clear the errors and see if they come back after driving. We did a test drive and they did not pop up. The "Front electrovalve permanent fault" on the other hand was always there. I really want to get myself one of these Lexia connectors, but I am too scared to pick up a random set from Ebay having heard all the horror stories with regards to them not properly fitting with the Xantia mark 1. I just hope to at least start out with ruling out the ECU problem by replacing it in the garage to test. Next step will probably be testing the electrovalve itself and looking into a different hose.

Appreciate the help!

[xantia_v6]

Chris gave good advice on diagnosing the electronics. On the S1 Xantia, the hydractive warning light is the light in the sports mode switch on the console, but it is usually very difficult to see in daylight.

There is no path that LHM can internally leak into the electrical connector of the valve, as the coil assembly is separate from and surrounding the hydraulic part. It is possible (especially if someone has opened up that valve) that it is leaking around the hex nut where the leak-off hose connects.

I see that your ECU has 2 protection diodes fitted on the driver circuits (which is generally a good thing) have you tested that these diodes are OK?

[white exec]

Yes, you can just pull off the return hose from the EV snout. No need to de-pressurise, as it's just a (very low pressure) feed back to the reservoir. Then attach some clear hose to check what comes out each time the EV switches on-off. Internal diameter of the hose would need to be about 3-4mm.

Yes I was thinking of XM (which also has Hydractive 2) and the same suspension ECU on the later cars (although differently programmed sensor thresholds). I'm surprised that there is no "suspension light" on a hydractive Xantia . . . maybe the one in the Sport/Normal switch also acts as a system monitor?? Even when the switch is set to Normal, does its light come on briefly when the IGN is switched on? Sorry not to know: my Xantia was non-HA, so only an XM here Hydractively. Plenty of Xantia experts here, though!

In retirement, I went without an oscilloscope for years, but finally got one of these small hand-held jobbies, which actually works rather well:
https://www.amazon.co.uk/ARCELI-Handhel ... 264&sr=8-1

[xantia_v6]

I think that your return hose may be split just above the clip, and if that is the case, it can be shortened by 25mm. I think that the hose in question is tee-ed into the pressure regulator return hose and not a separate part, thus tricky to replace. If you disconnect it with the engine running, you will get lots of LHM flowing from the other direction.

[inooid]

Hi all, update from my side. I went to a garage in The Netherlands that is hoarding up on (old) Citroen parts (Jan van Gompel) and was able to swap the Hydractive ECU with a new one and for the first time since forever the car is actually like a magic carpet again! I've gotten so used to the firm suspension that it even feels strange driving with the system fully working again.

I've brought the old one back with me and will be trying to desolder the solid state relays for the ones I bought to see if I can revive this ECU. Having a spare is probably not bad or selling it to a forum member is probably also a great option. I'll see if I can either make a video on how to desolder the relays for fellow rookies like me (definitely not experienced, but I'll give it a shot). I'll check if the new one has the diode mod and otherwise I'll see if I want to go for the cable diode mod or just soldering it in the ECU itself (like the old ECU).

Thanks for everyone's help! I'll keep an eye out on the hose and see if that needs any fixing in that regard. I am SOO happy that I can drive the car with the intended suspension. My dad gave me this car when he bought a new one as he knew I would take good care of it and I will now finally be able to show him that he's been driving with firm suspension all these years haha!

[white exec]

That's great news - well done in finding that.
As the new unit is new and working aok, maybe an idea not to start modifying it (with the protection diodes), but fit them externally on the wires leading away from the ECU connector.

Do post a link to the NL garage that has the stock. Could be useful to those of us with some older Citroens.
_________

Just in case it's of any interest, many of us have fitted not just the two protection diodes, but - on a good few XMs - a pair of dash LEDs, show when the suspension is Soft (LEDs on) or Firm (LEDs off). This allows easy monitoring of what the suspension mode is doing, and an easy check on the action of all the sensors while driving. A simple switch down to Gnd can exitinguish the LEDs.

With the resistors specified, the LEDs will clearly show up the 0.5sec pull-in each time the EVs switch on, and then fall back to lower brightness for the hold-in.

This is an extract from Gabor's XM circuit diagram, showing both the optional diodes and LEDs. Both connect into the same points (pin 1, pin 2) on the ECU connector. Xantia arrangement will be similar...
.

[inooid]

Thanks for that Chris! I've been scavenging all across the forum for this detailed schema, this is awesome! Now I have one more thing to find, which is the person that tried to rebuild the hydractive ECU using a Raspberry Pi or Arduino. I've found some old posts referring to this, but never actually found the source or any further readings. I guess it was only a wild dream.

As for the diodes, I think that might be a better idea indeed. I mentioned "new", but actually they're used parts, so don't want to confuse anyone there (used "new" as in new and old ECU). I've updated the post to add a link to the garage with all the parts. The website is Dutch, but they ship all around the world. When I was there they mentioned they had a couple packages shipping to Japan, so if you're in need of something I would say it's worth reaching out through their website.

If I'll get around to adding the LEDs, I'll make sure to post it. Perhaps make a couple videos to help others out in need to keep the knowledge stream going. I've also vaguely read somewhere that the Xantia's dashboard lights actually were intended to have the same dashboard light as XM for "sport" mode, but they removed it before release. I'll see if I can still find some traces of that anywhere and see if I can bust that myth.

[white exec]

The author of the XM "Circuit Diagram Project" is Gabor Deak Jahn, based in Budapest. He runs both BX and a 2.5TD XM. The pdf is a free download.

Their website is citroen.tramontana.co.hu, where you will find both the "bible" document The Citroen Technical Guide, the Circuit Diagram Project, and lots of good information about hydropneumatic Citroen systems and the cars.

Gabor has recently contributed here (as "djg"), as well as for some years on Club-xm.co.uk, along with several more of us on FCF.

Thanks for adding the parts dealer link!