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.