Height Corrector?

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KevMayer
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Post by KevMayer »

I am amazed at the amount of feedback so soon.

Thanks Mandrake. I'll try a few things tomorrow and report back.

cheers,

Kev
Cheers, Kev

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AndersDK
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Post by AndersDK »

Simon -

I really ought to send you a pat on your shoulder 8)
Never heard of this Hydractive ECU cycling before.
Whats the issue on those "snubber" diodes ? Is it simply corrosion that damage these diodes ?

PS : readers not familiar with diodes connected (in parallel but reverse polarised) to electrovalves or relay coils - should know that these diodes prevents the reverse polarity EMC energy from the coil once its disrupted from its feed voltage. Its the same effect as if you play with a good old battery door bell at home - and you suddenly get a hefty electric shock from a 2 x 1.5volts battery circuit :lol:
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Post by Mandrake »

AndersDK wrote:Simon -

I really ought to send you a pat on your shoulder 8)
Never heard of this Hydractive ECU cycling before.
Me neither, but there was mine doing it right before my eyes :?

I have had an LED on the dashboard connected to the front Electrovalve feed for a couple of months now to help diagnose the ride problems, and I noticed it was flashing between bright (full 12v) and dim (3v pulse waveform) randomly, but only after I had replaced the front electrovalve with another S/H one a week ago.

It turns out this S/H one is mechanically ok but the diode is faulty. (I can swap the good coil/diode sleeve from my old one to get a fully working unit)

Sometimes the LED was blinking and the Electrovalve was silent, sometimes the electrovalve was making a quiet clicking noise, and sometimes it was clicking loudly between open and closed mode, and it was randomly varying between these extremes as I watched.
Whats the issue on those "snubber" diodes ? Is it simply corrosion that damage these diodes ?
I don't know for sure, as it's embedded into the moulded plastic with no way to get at it apart from cutting it apart. However the symptoms suggest that the diode junction itself is not faulty - otherwise it would have failed and stayed completely faulty, as diode junctions don't normally "partially" fail.

Instead it behaves as if there is an intermitant high resistance connection to the diode (dry joint?) which is possibly varying with heat and mechanical vibration. I tested the diode was "ok" before fitting the S/H electrovalve to the car, and it measured ok at that time. (Only a week ago)

I was able to confirm with certainty that the diode is the fault by connecting an external diode to the electrovalve feed at the computer end while the symptoms occured, and immediately the symptoms stopped and the valve worked normally. Disconnect the diode and the intermitant symptoms and clicking return.

It seems that the computer is able to detect the excessive back EMF with the diode faulty and cycles the power between 12v and 3v in an attempt to "reset" the valve.

The good news is that anyone with this problem can just connect an external diode, which is much cheaper than a new Electrovalve :lol:

I am thinking of connecting an external diode to both front and rear electrovalve feeds as an insurance measure against ever having this problem again...as it seems like the built in diodes may not be as reliable as they could have been...
PS : readers not familiar with diodes connected (in parallel but reverse polarised) to electrovalves or relay coils - should know that these diodes prevents the reverse polarity EMC energy from the coil once its disrupted from its feed voltage. Its the same effect as if you play with a good old battery door bell at home - and you suddenly get a hefty electric shock from a 2 x 1.5volts battery circuit :lol:
Yes not only that, when you drive a relay coil/solenoid with a pulse waveform, if the reverse diode is not present the solenoid will drop out between the pulses as it relies on the diode to prevent the magnetic field collapsing completely between each pulse.

Regards,
Simon
Simon

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Post by deian »

Ohhh Simon, this is going over my head now, I think we've clearly established that my car is stuck in hard mode (well from what i think).

So where are the electrovalves? and where/how do i bypass the old diodes? Your technical talk between AndersDK has scared me a little. If/When you get round to sorting out the technicalities could you post some hints for me/us?

Thanks
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Post by Mandrake »

Hi deian,

Not sure if its a good idea me posting this as I may get you into a bit of trouble if you're not handy with a soldering iron and/or electrics, but if you're not maybe you have a friend who is, and other people may be interested in the info as well...

For reference here is where the front Electrovalve is:

http://homepages.igrin.co.nz/simon/imag ... -block.jpg

The Electrovalve screws into the main Hydractive control block.

The rear one looks identical but as its under the back of the car forward and to the right of the spare wheel carrier I didn't take a picture! (The car needs to be up on ramps at the back with the spare wheel carrier removed to access it)

If the issue is the diode being faulty, a substitute can be connected externally and as you can probably see from the picture there isn't anywhere convienient to do so near the electrovalve, so I decided to do it right back at the computer, inside the ECU box.

First I found the right wires and prepared them:

http://homepages.igrin.co.nz/simon/imag ... iodes1.jpg

The two white wires are the Electrovalve feeds one to front and one to rear, while the two thick green striped yellow wires are earth. (Not to be confused with the thinner solid green wires)

Didoes connected:

http://homepages.igrin.co.nz/simon/imag ... iodes2.jpg

Insulated:

http://homepages.igrin.co.nz/simon/imag ... iodes3.jpg

You can't see in the picture but the diodes are insulated from each other before applying an outer layer to make the whole lot insulated. (They're inside a plastic box but hey, call me paranoid...)

I used some 1N4006 which are 1 amp mains rectifier diodes, but any 1 amp or better power diode should be fine.

Regards,
Simon
Simon

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Post by deian »

Thanks Mandrake

I will crawl under my baby tomorrow and do some spying on the electrovalves, I may try some WD40 on the connectors first, or check for a good connection at the plugs into the electrovalves.

What type of diodes were they again?

Do i need to do both?

I may do a slightly different job, by building my own 'plug in diode' thing and preparing the wires for the 'plug in diodes' alternative diode route. Break out box style. But i get the idea.

So tell me, did it solve the problem?

Thanks
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Post by Mandrake »

deian wrote:Thanks Mandrake

I will crawl under my baby tomorrow and do some spying on the electrovalves, I may try some WD40 on the connectors first, or check for a good connection at the plugs into the electrovalves.
Yeah good idea, I've done that on mine in the past, although I use LPS1.
What type of diodes were they again?
I've edited my post to include the type I used... but they're not critical. Any 1 amp power diode should do.
Do i need to do both?
Well are both ends playing up or just one ? :)

On the other hand there is no harm in connecting the external diode when the internal one is still ok - but you now have a backup...
I may do a slightly different job, by building my own 'plug in diode' thing and preparing the wires for the 'plug in diodes' alternative diode route. Break out box style. But i get the idea.
You mean make a plug/socket adaptor to plug in line with the cable at the electrovalve end ? Yeah thats a good idea and would work fine. I considered doing it that way too but I had trouble buying the plugs and sockets used on the Electrovalve. You may have more luck there...they do look the same as many of the plugs used on the engine so somebody should sell them...

Just be careful to get the diode the right way around or it could damage the computer. The electrovalve has + and - symbols on it next to the plug so you can use that as the reference.
So tell me, did it solve the problem?
Of the front sticking in hard mode ? Yes it did.

Now thats out of the way I'm chasing an air leak problem with the hydraulic pump trying to determine if its only the pipe from the tank to the pump leaking or whether the pump itself is sucking in a bit of air.

I connected a length of clear hose to the overflow return at the tank and sure enough there are bubbles going through quite often, so there is definately air getting in.

It doesn't take much air to cause a harsh ride on broken surfaces like potholes... :x

Regards,
Simon
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Post by deian »

Mandrake.... maybe I have THAT problem too! harsh ride on broken road! You're creepy mate! :evil: But I'm glad you share my problems. :lol:
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Post by DoubleChevron »

Hi Guys,

I get the "sudden drop" occasionally. STOP PANICING and don't tamper with the car.

What is happening (especially with an Activa) is you are starting the car and immediatly driving off. At some stage later the anti-sink differential valve will open sending the rear plumeting to it's bump stops until such time as the pump can re-supply enough juice to lift the back up.

The simple fix is to rev the motor gently and wait for the car to build up full system pressure (and allow the anti-sink/differential valves to open).

You will never find the problem on older hydraulic Citroens as you have an enforced wait until the car lifts and all the hydraulics are pressurised. I don't really like the way the Xantia can allow the driver to move off before everything is pressurised (due to the anti-sink valves still holding the car up).

This happens most noticibly with mine if I leave the car on high, come back some time later and start it, the car will bounce and 'n' down at the front very strangley as the anti-sink valves open, allowing the front to plummet to earth, rapidly followed by the front rapidly rising back to high as the pump re-supplies the required pressure to the front.

ie: it's working as designed ... leave your cars alone :)

seeya
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Post by Mandrake »

Hi Shane,

Nice try. :lol: But it's not the anti-sink valves that cause that its the Hydractive Electrovalves. I've never seen it happen on the other two Xantia's I have contact with, and neither of those has Hydractive 2.

I think you'll find that the people that describe this problem are in fact waiting for the car to go up, as I always do.

At it's worst I would start my car, wait for it to fully lift, and drive off, and the back was stuck in hard mode then 50 metres down the road the back suddenly drops and corrects, and is soft again. This is NOT normal.... :roll:

I havn't had one single occurance of the back doing that in the 2 weeks since I fixed the rear electrovalve. Furthermore, the car no longer pops up in the air when going from maximum height to normal height, which is another symptom of the same problem.

When the Electrovalves are working properly you'll notice when you start the car after sitting overnight that the rear will drop just a fraction (about half an inch) just before the STOP light goes out, and before it starts to lift.

This is the Hydractive unit switching to soft mode causing pressure equalization to the middle sphere as soon as enough pressure builds up to allow the Electrovalve to operate.

When misbehaving (due to either a weak spring or faulty diode as described) it often waits until nearly full system pressure is reached. (and even then it can take a bit of vibration to jolt it into switching)

By the way Shane the strange "bouncing up and down" you refer to after parking the car with the suspension up is also related to misbehaving electrovalves...mine doesn't do anything like that now.

Regards,
Simon
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Post by DoubleChevron »

Hi Simon,

on a similar vein, even if it's the hydractive valves, the fact it only does it once 30second after startup ..... then never again ..... Never ever does it do it again once everything is at the right pressure, says to me there shouldn't be a problem. If we have sticking hydractive valves this would be very noticible all the time, not just 30seconds after the car has stopped.

It does sound like you have found a fix, I'm happy to leave mine as is though :) If it's not broken ............................................................. :lol: :lol: :roll:

seeya,
Shane L.
'96 Big BX 2.1TD exclusive slugomatic (aka XM)
'85 CX2500 GTi Turbo Series II (whoo hooo)
'96 Xantia VSX slugomatic (sold !!)
and of course, lots of old Citroens, slowly rusting away in pieces ;)
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Post by xantia_v6 »

Simon,
Good work on finding the spring problem in the electrvalve!
I believe that at least the back end of my car has this problem.
You said that the electrovalve is difficult to disassemble, is this just due tp the locking compond on the threads?
If this problem is as common as I suspect, then it is worth thinking about whether the factory fitted springs that are too short? or are the springs settling with age due to being made from the wrong material?

Do we have any idea what the original length of the spring is?

If people are going to be dismantling their electorvalves to check this, it would be worth doing a survey of the free length of the springs removed, as at least some of them will still be factory length.

re the diode, I think that the diode is origninally fitted in the solenoid to reduce RFI. It is many years since I needed to know about designing this sort of circuit, but I seem to recall that the switching time of the diode causes high frequency current spikes around the circuit, and the radiated energy is proportional to the length of the diode/coil circuit.

regards,
Mike
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Post by Mandrake »

xantia_v6 wrote:Simon,
Good work on finding the spring problem in the electrvalve!
I believe that at least the back end of my car has this problem.
You said that the electrovalve is difficult to disassemble, is this just due tp the locking compond on the threads?
It's two things. One is the thread locking compound makes it very difficult to unscrew it. I found that by putting it in the oven at 70 degrees for 10 minutes it seemed to make the difference that allowed me to break the thread lock compound without damaging the unit.

I'd previously been warned by two different people that they had snapped the neck of an electrovalve trying to get it open, so I took the warning seriously, and didn't attempt to do so until I had already obtained a S/H replacement valve.

The other difficulty is in figuring out how to reassemble it - the assembly order and orientation of the two springs, the sleeve, and the pin is NOT obvious at all.

I studied it and tried different approaches for half an hour with no success, and finally remembered that bernie had forwarded me a couple of exploded view pictures from someone else (thanks bernie!) some time before and there was just enough picture detail for me to make out the correct assembly. I made sure to take my own pictures once I figured it out too....
If this problem is as common as I suspect, then it is worth thinking about whether the factory fitted springs that are too short? or are the springs settling with age due to being made from the wrong material?

Do we have any idea what the original length of the spring is?
I think they might have just settled with age... most springs eventually lose a bit of tension, and it could be as simple as the original length being marginal, and a loss of tension with age.

The ones that I took apart had the spring only reaching the base of the taper on the end of the spring - which is only JUST long enough for the spring to touch the groove at the end of the valve, let alone put any tension on. I would guess that originally they were the same length as the tip of the taper, giving about 1mm of compression, but I decided to give it a little bit extra.
If people are going to be dismantling their electorvalves to check this, it would be worth doing a survey of the free length of the springs removed, as at least some of them will still be factory length.
I don't know that people pulling apart their valves willy nilly is a terribly good idea! :? I tend to go to extreme lengths to solve problems that I feel should be within my grasp, and sometimes take a few calculated risks that many people would not, and which I certainly don't feel comfortable advising other people to do.
re the diode, I think that the diode is origninally fitted in the solenoid to reduce RFI. It is many years since I needed to know about designing this sort of circuit, but I seem to recall that the switching time of the diode causes high frequency current spikes around the circuit, and the radiated energy is proportional to the length of the diode/coil circuit.
Yes you're probably right about causing less RFI with the diode at the solenoid end of the cable run, than the other end, although the switching frequency is only 1Khz.

The problem with the diode is it isn't just there to protect the computer from the back EMF and minimize RFI, the solenoid won't actually stay engaged when driven by the pulse waveform with a faulty diode :(

Regards,
Simon
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Post by Mandrake »

DoubleChevron wrote:Hi Simon,

on a similar vein, even if it's the hydractive valves, the fact it only does it once 30second after startup ..... then never again ..... Never ever does it do it again once everything is at the right pressure, says to me there shouldn't be a problem. If we have sticking hydractive valves this would be very noticible all the time, not just 30seconds after the car has stopped.
Hi Shane,

Mine was like that originally - only stuck during startup and lifting, but towards the end of its "life" it started to stick intermitantly during driving too.... it got as bad as about a 1 in 5 chance every time it switched from hard to soft it wouldn't actually switch, and would stay stuck in hard.

When you consider how many times the computer switches modes during a single trip thats a problem... :(

It does sound like you have found a fix, I'm happy to leave mine as is though :) If it's not broken ............................................................. :lol: :lol: :roll:

seeya,
Shane L.
Sounds like your one is not too bad, but if it ever gets worse, you know what to do..... :lol:

Regards,
Simon
Simon

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2016 Nissan Leaf Tekna 30kWh in White

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