Hydractive Repair Kit

[Mandrake]

Right, I’ve just gone out and tried bouncing the suspension with the engine running as I couldn’t remember if it was running before or not. With the engine running and a door open the back of the car was nice and soft as before, and the front was pretty much rock solid, even with all of my weight I could only move it about 1 cm.

Ok, thats definately not right.

I tried closing the door and leaving the engine running, but the car wouldn’t switch to hard mode, so I turned the engine off, closed the door and eventually heard a loud click as it switched into hard mode. The back of the car was now rock solid and wouldn’t move at all,

Are you sure its rock solid ? It will have very slow damped movement but it will move - if you sit on the boot and get someone to measure how much the car goes down it should still go down at least 20mm.

the front of the car seemed pretty much the same as before, maybe slightly stiffer but I couldn’t decide if this was just my imagination or not, the difference definitely wasn’t as noticeable as it was on the rear suspension.

If theres no change theres definately a problem. The difference between hard and soft modes is like day and night.

Regards,
Simon

[Mandrake]

Even in hard mode it should be possible to press down on each wheel - like you press down a coil spring.

Hi Anders,

Have you tried bouncing the front of a Xantia in hard mode ? I can assure you that it is very stiffly damped. It's not possible to open the washer/threshold valves in the sphere necks by a manual bounce test, so all you are testing is the oil flowing through the tiny bypass hole which is 0.7mm at the front, (compared to 1.5mm of a standard Xantia) and when trying to do a manual bounce test subjectively it feels almost solid.

If I sit on the front (80Kg) in hard mode it goes down about 20mm, in soft mode it bottoms the front suspension - big difference. There is nothing wrong with the strut spheres on my car - they are on pressure.

IMHO the state of the strut spheres in a Hydractive 2 Xantia cant be judged by a simple bounce test because the damping is simply too stiff.

My pennies are on 2 shot front wheel spheres on your Xantia
Its got nothing to do with hard/soft mode working or not.

Well apart from the fact that he says he's just replaced all the spheres it doesn't fit the symptoms.

If the strut spheres were flat but the centre hydractive sphere was ok then it would be rigid in the hard mode, but still quite soft in the soft mode for a bounce test - but it's stiff in both modes, and equally so.

So if it's stiff in the "soft" mode then it MUST be either the centre sphere, or failure of the centre sphere to be switched into circuit, for example an electrovalve fault.

It's possible that in addition the strut spheres could be poor as well, but that doesn't influence the above.

My first bet is that the front electrovalve has the diode fault - the front ones seem to fail well before the rear ones - perhaps because of exposure to engine bay/radiator heat. The diode modification is a simple and relatively cheap thing to try (much cheaper than a replacement electrovalve) so I would try that first.

Another way to test it would be to manually power the electrovalve - unplug it, and connect 12v to it (via a 5 amp fuse!!) and see if the car switches to soft at the front. Note: polarity is crucial, because of the internal diode, if you get it the wrong way around it could damage the diode, although hopefully the fuse would prevent that.

Also don't run it for more than about 1 minute with full voltage or it will overheat. But for a quick test it will let you know if you're on the right track.

Regards,
Simon

[AndersDK]

I repeat :
Its got nothing to do with the hard/soft switching works or not

As long as the suspension is raised to normal height - each corner should STILL press down like a coil spring when spheres are good. This is true whenever the extra sphere is connected *or not* by any mode switching.
There is no rocket science to that bit - however many pages of Citroen manuals you study.

Only science thing is WHEN the computer decides to switch mode. But thats not relevant here in a simple test for state of the spheres.

KISS = Keep It Simple Simon

[Mandrake]

I repeat :
Its got nothing to do with the hard/soft switching works or not

As long as the suspension is raised to normal height - each corner should STILL press down like a coil spring when spheres are good. This is true whenever the extra sphere is connected *or not* by any mode switching.
There is no rocket science to that bit - however many pages of Citroen manuals you study.

Only science thing is WHEN the computer decides to switch mode. But thats not relevant here in a simple test for state of the spheres.

KISS = Keep It Simple Simon

Hi Anders,

I respectfully suggest that when one day you own a Hydractive 2 Xantia of your own and need to perform fault finding on it, that your opinion on this will change. There is nothing like first hand experience of something to give true insight into how it works and it's comon failings.

I'm just offering advice for finding this fault based on my own experiences of an almost identical fault that I had and solved on my car, using diagnosis techniques I formulated myself based on an understanding of how the system works, not based on theoretical readings of books. (Although having the reference material available certainly helps)

Readers are (as always) able to make their own judgements on the merits of any advice given on this forum - it's up to the individual to take or leave advice from any given member on a given topic, and the proof of the pudding is always when the problem is finally solved.

And thats about all I'll say on the subject.

Regards,
Simon

[CitroJim]

I will agree entirely with you Simon,

The front in hard mode is as hard as a rock on the bounce test. You can get movement but you need to really put your weight (of which I have little ) into it. This fooled me at first until I followed your Posts Simon, and diagnosed the front electrovalve diode faulty and thus not switching into soft mode.

Anders, in hard mode, the front suspension feels like my 205GTi. That has practically no movement at the front on a bounce test!

In soft mode the difference is rather significant, it goes very soft indeed and is easy to bounce to the limits of suspension movement.

The difference between hard and soft at the rear is easily noticed but not nearly as much as the front difference.

I test like this: Switch off engine, open and close door and listen for clicks, bounce each end in turn continually whilst listening for the click of the electrovalve releasing back into hard mode after 30s and feeling the difference in bouncing as it does. If you bounce once or twice in soft mode and then wait and bounce after the switch you may not feel the change, alweays best to bounce continually and then you can really feel the change on the transition from soft to hard.

It must all look very strange to any innocent bystander but at least I know all is well in the Hydractive department. How I wish there was such a simple test for the Activa Electrovalve

[CypherPunk]

Thanks for your help Mandrake. Anders, I know what you mean about keeping it simple, that's why I changed all of the spheres on the car just to rule them out as a problem.

Are you sure its rock solid ? It will have very slow damped movement but it will move - if you sit on the boot and get someone to measure how much the car goes down it should still go down at least 20mm.

It seemed pretty much solid, however I only really gave it a quick shove to check that the car was in hard mode, I'll double check next time I go for a drive though.

My first bet is that the front electrovalve has the diode fault - the front ones seem to fail well before the rear ones - perhaps because of exposure to engine bay/radiator heat. The diode modification is a simple and relatively cheap thing to try (much cheaper than a replacement electrovalve) so I would try that first.

Another way to test it would be to manually power the electrovalve - unplug it, and connect 12v to it (via a 5 amp fuse!!) and see if the car switches to soft at the front. Note: polarity is crucial, because of the internal diode, if you get it the wrong way around it could damage the diode, although hopefully the fuse would prevent that.

Would the kit mentioned in the first post work with my Xantia, I'm guessing that the HA2 computer would be located somewhere else on the XM, but apart from that surely the principle is the same?

I’d love to save myself some money by checking it first and soldering the diodes myself, but I’m not brilliant at soldering and just don’t have the time at the moment.

[CitroJim]

Would the kit mentioned in the first post work with my Xantia, I'm guessing that the HA2 computer would be located somewhere else on the XM, but apart from that surely the principle is the same?

I’d love to save myself some money by checking it first and soldering the diodes myself, but I’m not brilliant at soldering and just don’t have the time at the moment.

Yes, it indeed will, without any worry at all. I have been in touch with the vendor of the product and he will be releasing a Xantia version soon. he is presently doing his research to ensure the installation is absolutely correct as regards wire identification. Simons Post (which I quoted in my reply earlier in this thread) gives the wire colours for MK1 Xantias. On MK2 (facelift) versions, the wires in question are grey. The HA2 ECU is located with the Engine ECU in the box on the offside inner wing. Buy with confidence, he is very good and knows his stuff.

I would agree that unless you are 100% confident in your soldering ability and getting the diodes the right way round, the kit as offered by e-crofting makes a lot of sense.

I've just bounced mine in hard mode, pushing on the edge of the wing, this 10 stone weakling can only get about 3/4" movement pushing with all his might

[AndersDK]

Have you tested for binding struts ?

This shows like the car raises in small steps like something is holding it down and suddenly releases it. Commonly followed by a "dry" sliding sound.
How does the suspension behaves when doing the Citaerobics ?

[I've just bounced mine in hard mode, pushing on the edge of the wing, this 10 stone weakling can only get about 3/4" movement pushing with all his might

Thanks Jim
At least it shows the hard mode is not rock solid - as for a simple KISS test I tried to explain with my humble foreign english language 8)

(Are you absolutely sure it was not the tyre you compressed )

[DickieG]

With my Activa suffering from a hard ride at the front and too soft at the rear, I've been carrying out numerous tests on both that car and my 'spares' Activa, whilst using the VSX and V6 as points of reference (VSX and V6 are definately working correctly) in order to determine what if anything may be wrong.

It passed the bounce/door open test which suggested that the Hydractive blocks/diodes were working correctly, which had somewhat confused me .

I swapped ECU's but that made no difference. When I tuned the radio to 171 LW to listen to the switching points (not so easy on petrol cars due to interferance) on both Activa's the switching would stop after a few minutes, and be replaced by a brief periodic pulse (this was obviously the ECU trying to reset the diodes in the blocks).

As a result I've just fitted new diodes as per Simon's suggestion which I'm very pleased to say has solved both problems

Being the idiot that I am, I didn't realise that I have in my possession the full Technical Training manual for the Activa Hydractive system which includes a detailed wiring diagram for the system. As Citrojim states the wiring running to the 3 Activa Hydractive blocks is grey rather than white, but they can be identified by the following numbers printed on each wire; front 7720, rear 7730 and SC/CAR/Activa 7723.

On Activa's when a fault is detected on a Electovalve, the Hydractive blocks switch to firm (default), whereas the SC/CAR/Activa one stays soft (default).

Possibly the easiest way of finding out whether the suspension is switching when the engine running is to blip the throttle which switches the suspension briefly to firm, however, one thing to bear in mind is that after the ignition has been switched on, the vehicle has to have exceeded 5 km/h once in order to switch to the firm state.

I've also noticed that when the front Hydractive block switches over, the switch 'clunk' can be felt through the bonnet shut panel (handy with the noise from the engine). The switching 'clunk' can also be heard within the car when stationary.

A big thank you to Simon for his help with this, if anyone can read French, it's also shown on the following link http://activaclubfrance.free.fr/Entreti ... liques.pdf

[CitroJim]

(Are you absolutely sure it was not the tyre you compressed )

Ohh yes, almost all of the 3/4" is suspension movement Anders Activa front tyres inflated to 2.5 Bar are not easy to compress at all !!!!

As a result I've just fitted new diodes as per Simon's suggestion which I'm very pleased to say has solved both problems

Excellent news Richard I'll wager you did a neater job of installing the diodes than I did I was rather embarrassed at mine when you saw it but it is only temporary wiring pending the LED fitting

Thanks too for the wire numbers. Very valuable. I'll now know precisely which LED relates to which electrovalve

[CypherPunk]

I test like this: Switch off engine, open and close door and listen for clicks, bounce each end in turn continually whilst listening for the click of the electrovalve releasing back into hard mode after 30s and feeling the difference in bouncing as it does. If you bounce once or twice in soft mode and then wait and bounce after the switch you may not feel the change, alweays best to bounce continually and then you can really feel the change on the transition from soft to hard.

I've just tried this test, and, to my annoyance, I could definitely feel the car switch into hard mode on the front, it's very slight but it’s definitely switching properly.

Which just leaves me more puzzled than before, as I’ve said, all the spheres are new, the car rises and falls pretty smoothly, it occasionally lurches slightly when rising, but it’s nothing compared to my old car, which jumped up and down and groaned at the same time.

I’ve not checked the suspension height properly, but it looks exactly the same as my neighbour’s Xantia HDI, I’ll have to get around to checking it at some point though.

The only thing I can thing of is that perhaps the front centre sphere is duff, or I was sent the incorrect type by GSF, but that just seems like clutching at straws.

Any other ideas?

[CitroJim]

I'd suspect the new sphere last of all given it's the right one. Check and positively confirm although GSF are normally spot-on. A Hydractive outer (strut) Sphere has a tiny hole (damping) and the Hydractive Centre Sphere has a big hole like an accumulator sphere. You could get the effect you have if you have inadvertantly used a strut sphere in the centre.. Unlikely I know but do check.

All the spheres I have got from GSF recently have their application written on them in reasonably plain english.

Have a read of this thread: (bedtime reading for all Hydractive owners )

http://www.frenchcarforum.co.uk/forum/v ... harsh+ride

It is very long but contains a goldmine of information on this sort of problem, particularly the words about insufficient hydraulic pressure to properly operate the electrovalves.

You'll surely find the answer in the above thread.

My money is on the diode.

Finally, have you done loads of Citarobics to purge all air from the system? An airlock in the Hydractive block could cause this problem.

[DickieG]

I've just tried this test, and, to my annoyance, I could definitely feel the car switch into hard mode on the front, it's very slight but it’s definitely switching properly.

Which just leaves me more puzzled than before, as I’ve said, all the spheres are new, the car rises and falls pretty smoothly, it occasionally lurches slightly when rising, but it’s nothing compared to my old car, which jumped up and down and groaned at the same time.

Take a closer read of my post above, my Activa was OK on the bounce test.

If you buy new diodes from Maplin the repair will only cost 28p which must be the cheapest repair for the money on any car let alone a Hydractive Xantia

[CypherPunk]

I'll probably buy one of those repair kits anyway, although I'm not totally convinced that it'll work, at least it eliminates a possible problem down the line.

As I’ve said, I'd love to solder it myself, but I’m absolutely rubbish at fiddly jobs like that, plus I'd need to go out an buy myself a soldering iron, which would probably cost more than the repair kit.

Also, what were Citroen thinking when they decided to attach the diodes to the electrovalve? Surely it would have been simpler to just put them on the HA ECU circuit board.

[CitroJim]

Also, what were Citroen thinking when they decided to attach the diodes to the electrovalve? Surely it would have been simpler to just put them on the HA ECU circuit board.

Strictly, the electrovalve is technically the right place for them. These diodes are to absorb the back EMF (ElectroMotive Force - a reverse voltage) produced by the solenoid coil when the magnetic field collapses or reverses. The diode, being a device that conducts in one direction only, presents a short circuit to the back EMF.

In effect, they do the same job as a condenser in a points ignition system. It is the back EMF of the magnetic field collapsing in the ignition coil primary winding as the points open that would otherwise cause a big spark at the points. The condenser absorbs theis back EMF and at the same time ensures that all the energy generated in the primary coil goes to create a nice fat spark at the sparkplug rather than a damaging and wasteful spark across the contact breaker points. It is not 100% efficient, hence why points burn evetually.

The diode on the electrovalve does the same thing. It effectively shorts out the back EMF produced by the magnetic field collapse and reversal. If it did not, the back EMF would act against the voltage trying to keep the solenoid in an operated condition and thus it would cause the solenoid to release or only half-operate. Exactly what DickieG observed earlier.

For maximum efficiency, the diode (or condenser in a points ignition) should be as near to the source of back EMF as possible. (i.e. against the coil) because long wiring induces inductive and capacitive reactances that can upset the working efficiency of the diode. In practice it works well enough when placed some distance away and if you look at the French document DickieG posted earlier you will see there actually are pads on the ECU circuit board to take the diodes.

The diode has a secondary function of protecting the ECU circuitry againt potential damage from back EMFs produced by the electrovalve coils. Being reverse polarity, this can cause sensitive semiconductors to fail although the HA ECU seems quite resilient even when the diodes in the valves fail.

I'm not brave enough to break into an ECU to fit them so they go outboard!!!

I second the advice of DickieG to either fit the diodes or get hold of the ready made repair kit. DickieG has shown that they can and do fail half way between being good and totally failed.