xantia_v6 wrote:aneesh84 wrote: However I must test that the electrovalves are operational, before ordering. Since all my spheres are completely flat and I do not have access to the accumulator sphere, the bounce test is not an option for me. I do have a multimeter which i could use to test the electrovalves, except that I do not know where exactly to measure the voltages across. Is it near the front hydractive sphere. Or is there another convenient location in the circuit to measure the voltages?
The most convenient point that I know of is the wire to the front electrovalve, which is part of the assembly that the hydroactive sphere attaches to.
You need to test with the plug still connected to the electrovalve, as unplugging it will stop the system from working.
With the valve activated you should see 4-6 volts on that wire.
Or you could just unplug it, poke the leads of a 100 ohm resistor in the pins in the plug, and measure across the resistor. It doesn't take much to fool the ECU into thinking an electrovalve is connected. Anything from about 47 ohms to 470 ohms will work...
Of course all we're testing here is that the ECU works, the electrovalve itself could still be faulty - only testing with a known good sphere will reveal that. Things that can go wrong with the electrovalve are:
1) The internal back EMF diode can go open circuit or have a high resistance soldered joint. In this case an external (reverse connected) diode can be fitted in the wiring loom. I did this on my previous Xantia and mounted them on the wiring harness inside the black plastic box that houses the ECU. (Documented in a thread on the forum somewhere) I have a feeling this failure mode is quite common, but easy to fix with external diodes.
Symptoms of this problem will be that the suspension will only go soft for half a second during a hard to soft mode transition, so it will be stiff most of the time but do little unexpected "jumps" in height. It will also be impossible to depressurise the hydractive regulator sphere, making changing the sphere difficult if not impossible. (At least without a lot of oily mess)
2) The internal connection between the connector and the coil itself can get a dry joint - intermittent high resistance - which sometimes changes with temperature. I had this on a front electrovalve where it would work when cold but when hot it would keep dropping out. Symptoms are the ECU constantly cycling in and out of hard/soft mode every few seconds, or the suspension just being hard sometimes when it shouldn't.
There's nothing that can be done to repair this internally - the coil sleeve is fully moulded and can't be disassembled, so it requires a replacement electrovalve - or at least the coil sleeve part of it, which can be carefully separated from the rest of the unit. (Making it possible to make one good electrovalve out of one with a faulty coil/diode and one with a faulty needle valve...)
3) The needle valve can become pitted or worn to the point where there is high bypass leakage either in the hard or soft mode, but seemingly usually in the soft mode, and usually at the front of the car. At lower levels of leakage this will cause a variety of symptoms as it drains the reserve pressure at the accumulator fairly quickly when the engine isn't running.
Things like the car not settling after getting out of it if you wait more than 30 seconds between turning off the engine and exiting the car, (since all the reserve pressure has drained away and the anti-sink valves have closed before you get out of the car) or sometimes a loud "groan" after you get out as the anti-sink valves are just on the threshold of closing as the height corrector attempts to lower the car...
If the leakage is really bad it will cause the car to take a lot longer to lift up and the suspension will sometimes not switch to soft mode at all, or will switch in and out of soft/hard mode when bumps are hit causing unusual ride harshness. Sometimes the leakage is such that you can hear a hissing noise if you turn off the engine and listen close to the location of the electrovalve - if you hear a hiss that stops when the electrovalve shuts off after 30 seconds with the doors closed and the engine off you know you have a leaky electrovalve.
Although it's possible to disassemble an electrovalve its quite difficult due to locktite holding the thread together, its easy to break them instead of unscrewing them, and even though you can fully strip down the needle valve I'm not sure what could be done to fix pitting on the valve and cure the leakage. Again its probably just a case of getting a replacement. If sourcing a second hand one from a wreck, I would recommend a rear valve - front and rear are identical but front valves seem to fail a lot sooner, probably due to higher suspension pressures that they are switching and engine heat.
I wouldn't let a faulty electrovalve put off the original poster as they can be sorted out, but a faulty ECU would probably lead me to just fit standard spheres and be done with it...