Adventures with a Xantia VSX and a C5 v6

[octinum]

Ah, does blink code work for Hydractive? I saw some resources using it for reading engine error codes, but not Hydractive.

I think it was something like shorting a pin (C2, IIRC) for x seconds, then watching the engine check light blink. I'll find the source and give it a try. The Lexia I have doesn't have the connector for Series 1 (I previously used it to diagnose my old C5), and it's the first time I'm hearing about "Elit" reader. thank you!

The suspension should go into soft mode when the car is stationary with the engine running, regardless of the dynamic sensors (steering angle and suspension movement), so you can initially ignore them (and the speed input sensor).

The first thing to check are the 2 power voltages (constant and ignition switched). Beyond that, it is most efficient to get the ECU codes. If you don't have a Lexia or Elit code reader, the hydractive ECU codes can be read with a simple blink code reader.

[xantia_v6]

I beleive that the hydractive ECU supports blink code reading, but needs an external LED on the line, not the built-in warning light. But if you have a lexia with a 16 pin connector, then you should be able to jumper to the appropriate pins on the 30 pin connector for the hydractive ECU.

See: viewtopic.php?t=49045

[xantia_v6]

After thinking about it, maybe the best thing for you to do is to get a 16 pin obd connector from another car and wire it into the car using the link above as a guide.

[octinum]

Thank you xantia_v6!

A bit of progress in terms of diagnostics: Constant and Ign. Switched fuses are working. I also tried cutting the external diode to the front electrovalve and I heard the "clack!" this time, at least what I think is the EV click. I'm assuming the diodes the previous person who worked on the car are also dead. Then again, the car is still in stiff mode; I sat on the front side and it only moves a couple centimeters or so.

This, I think, can point to a few causes:
- Dead diodes: According to the datasheet, VN05N SSRs in the Hydractive control unit have thermal shutdown feature. If the diodes are dead, VN05N temperatures would increase, causing shutdown (even if they aren't fried yet). Good news is, I should have some backup VN05Ns somewhere, and I have a spare Hydractive control unit I can work on. Bad news is that; I can't find either. So first thing to try is to fit proper diodes with high breakdown voltage specs.
- Dead VN05N or hydractive control unit: Should be quite rare to see the Hydractive control unit dead. VN05Ns are a more probable suspect.
- Spheres. I'm not hearing a lot of "clicks" from the regulator, but the center spheres might be low on pressure. I think the electrovalves need a certain pressure differential to work; the solenoid allows a "low power" valve which in turn activates the "main" valve which allows LHM to flow. So if that first "small" valve cannot work due to low pressure, the actual mechanism that allows LHM to flow wouldn't also work
- Internal leak in the electrovalves. That is the horror scenario. I'm not good at mechanical things, and I don't think I can find anybody who could work on the valves without killing them. Let's hope it doesn't come to this.

[xantia_v6]

Measure the voltage on each electrovalve when it should be in soft mode. If the electronics are correct, you will see a few volts (3V to 6V) continuously. If you see voltage for a second or so that then diappears, then there is probably as faulty diode or solenoid. If there is no voltage at all, then it would indicate a problem inside the ECU.

A leaking electrovalve is not too difficult to repair if you treat it carefully.

[octinum]

I could find some time to splice wires to add some test wiring to the Hydractive. Converting two automatic cars to manual at the same time took its toll, my tools and components are all over the place. Obviously, I couldn't find waterproof connectors and terminals quickly in Turkish conditions, so I had to make do with the last pieces I had at hand. Pardon the messy wiring, I'll tidy them up next week.

Anyway, observing by the advice from @xantia_v6 (must go into soft when the car is stationary and the engine running) confirmed I don't have soft mode. Then I spliced the electrovalve triggers to be able to make better measurements. A quick resistance measurement with the EVs disconnected showed that one of the electrovalves was good with around 4.3 Ohm resistance, but the other has failed in short circuit (zero resistance except for the multimeter probes).

The way Hydractive control unit works seems to be to supply 12V first (as documented elsewhere). When it detects a short circuit on one of the electrovalves, most likely as an overcurrent condition internally by the VN05Ns, it immediately shuts down both electorvalves.

But there was the possibility of Hydractive unit failing at the same time with the electrovalve. I don't know if it is also documented elsewhere, but I thought I could try to "fool" the H2 unit with some resistance. The ordinary resistors I use with my electronic circuits are 0.25W, so I needed something that could survive the testing. Enter P21W (or more accurately, P21/5W).




After crimping watertight connectors to each EV trigger, I separated the one with what I think has a short-circuit, and left the other connected. I connected a bulb holder to the splices I took from the separated one. When I opened and closed a door, the Hydractive control unit supplied 12V to both electrovalves, one of which at this point is simply the bulb. Hydractive control unit supplied 12V first, as seen from the bulb lighting up at full brightness, then switched to the PWM signal, which averaged around 3.x Volts, causing the bulb to "dim". With this, I was able to hear the front electrovalve buzz. So, rear EV is defective.

Laptop battery running low. I'm hoping I'll continue to document my progress.

[xantia_v6]

I can give some clarification of the operation of the hydractive drive circuits. The solenoids have quite a lot of inductance, so when 12V is applied the current in the circuit rises (relatively) slowly, taking a few milliseonds to reach full value. The solenoids are not rated for continuous operation at 12V, and will overheat if 12V is permanently applied.

The VN05 drivers initially apply 12V to the solenoids and sense the current in the circuit. When the current gets to the correct value the VN05 starts pulsing the voltage to maintain the desired current, with the current value being smoothed out by the inductance of the solenoids and the operation for the freewheel diodes (internal to the solenoids or the extra ones fitted externally).

When operating normally you will see 3-6V across the solenoid and hear the whistling of the VN05s switching.

The ECU may detect that your resistor does not have inductance and shut down after a few seconds.

[octinum]

Thank you! In my case, the ECU did not shut down for an extended period. I didn't pay attention to the conditions as I was focusing elsewhere, but I can say that the light stayed on for quite longer than a few seconds.

I can check VN05N datasheet for how it could detect no-inductance. Tomorrow is Sunday. Have some time to read.

I can give some clarification of the operation of the hydractive drive circuits. The solenoids have quite a lot of inductance, so when 12V is applied the current in the circuit rises (relatively) slowly, taking a few milliseonds to reach full value. The solenoids are not rated for continuous operation at 12V, and will overheat if 12V is permanently applied.

The VN05 drivers initially apply 12V to the solenoids and sense the current in the circuit. When the current gets to the correct value the VN05 starts pulsing the voltage to maintain the desired current, with the current value being smoothed out by the inductance of the solenoids and the operation for the freewheel diodes (internal to the solenoids or the extra ones fitted externally).

When operating normally you will see 3-6V across the solenoid and hear the whistling of the VN05s switching.

The ECU may detect that your resistor does not have inductance and shut down after a few seconds.

[octinum]

Captain's log, supplemental.

We're mostly back on the road. Suspension maintenance was performed last week:
- The three orings on the hydractive valve from the donor car were replaced, and the hydractive block from the donor car was cleaned&installed
- I added two 1N5408 diodes near the Hydractive control unit, along with two waterproof connectors of different type on the electrovalve triggers. The wiring is a mess tho, I'll fix some time
- All spheres were checked for pressure. We found that the anti-sink (rear brake accumulator) sphere was flat, and we replaced it. Living in Turkey: I think what I paid for a second hand anti-sink sphere amounts to around €130. 5 spheres were recharged in the end, one replaced; the other two were at correct pressure
- The rear "distributor-like" unit was replaced with the one from the donor car as the specialist caught a leak
- Some work on the brakes, which I'll explain below

I can confirm that the electrovalves do trigger now, so electronics-wise, we're there. Hydraulics-wise, I'm not sure. I still find the rear a bit stiffer than expected, even with sphere pressures up to spec. Possible reasons that I can think of:

- Clogs/varnish in the system. The specialist asked me to actually drive the car, saying "the car was in storage for 3 years, at the highest setting. There might be deposits in the hydraulic system, and the moving parts might need some exercise. Drive on varying surfaces for a couple weeks and come back". Made sense to me.
- Hydractive block not actually working: I think what electrovalve opens is kind of a "trigger", which opens up a hydraulic valve to connect the corners to the center (and to each other). If that's the case, I'm stuck; don't know what to do.

Also, the brakes are acting up. They never fail to stop the car, but I caught two distinct issues:
- Possible caliper/handbrake issue with the front left wheel. I noticed the car pulled left a couple times. I took the car for a drive last night, and felt the wheels (15" steel wheels) for temperature. The front left was noticeably warmer than the remaining three. In fact, the other three were cool to touch
- I drove the car for around 30+ kilometers today (15km school run to pick up the kid, 15km back home). I immediately checked the wheels, and this time all 4 wheels were quite warm to touch, borderline hot. It wasn't a sprited drive, with gentle acceleration and braking.

Neither of these happen all the time, and they didn't happen when the car was in the shop. The specialist said he actually caught some issue with the front right, and applied the caliper rebuild kit. I'm taking the infrared thermometer with me tomorrow to actually try and see the temperatures.

Next week we'll flush the coolant, filling with correct antifreeze ratio, and do the oil and filter change. And of course, fix the brakes, if we can.

As for the drive, as I noted in the following topic, so far so good:
viewtopic.php?t=90363

Perhaps the rear could improve, but of course that's something we'll see down the line. The kid especially liked the ride after my wife's Audi A3 which we were driving on the same route.

Oh, and the gearbox. I found it quite pleasant to drive. The gear ratios are a bit short to my liking, possibly due to the fact that the gearbox came from the 16v 132hp version (XU10J4?), which makes its torque higher up the rev range than my XU10J2. The clutch grabs quickly in response to my foot going up, and in a linear fashion, as opposed to what I felt with hydraulic clutches with CDVs and DMFs. Gear shift action is low-effort, with the occasional notchiness with the first gear. I am impressed after the Fiat Tipo 1.3 Multijet, Hyundai i20 whatever, and the Astra H 1.6 manual, all of which I tried for short periods of time.

[CitroJim]

Good to see some very positive progress An interesting read, thank you

[octinum]

Thank you guys, gals, and the forum in general! I don't think I would be able to save the Xantia if it weren't for you.

Anyway, back from school run. 15 kilometers trip, in half an hour. A few kilometers of light stop-go traffic; the rest is higher speed stretches separated by traffic lights a few kilometers apart. The brake side of things is worrying, so we go for the brakes next. Here are the temperatures, on steel rims and the discs as best as the infrared thermometer can measure through the holes of said rims. All in degrees Celsius.

FL disc: 116
Fl wheel: 82

Fr disc 85
Fl wheel: 50

Rr disc: 75
Rr wheel: 40

Rl disc: 75
Rl wheel: 45

I drive conservatively, even when I am at speed, akin to pulse-and-glide. Front left seems to indicate to the handbrake. But the others seem high to my eyes too. The car was lightly loaded; 80kg of me, a 10 year old girl, and a 5 year old girl.

I think I should first rebuild the spare brake doseur valve at hand, replace the one on the car, and replace the handbrake cable at the same time, at least for the left side.

Good to see some very positive progress An interesting read, thank you

[octinum]

Oh, a photo, of course! Once mechanicals are complete, a full polish is in order. There are a couple places where clearcoat failed --- top of the bootlid will need a respray, most likely, and a section on the roof which I might save with some sanding and polishing. I'll leave the fender-bender battle scars for some other time. It's an ongoing project.