Electrovalve diodes - Myth or real?

xmexclusive · Post by **xmexclusive** » 15 May 2009, 09:26

Hi All

List of XM Suspension ECU's.

Mk1 XM types:

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Valeo Suspension Variable
73800802 - 12v - 49.89
Smooth Die Cast Alloy Case painted Black with thin pressed steel lid.
Has a White 15 pin connector and a Green 15 pin connector each with external polarisation ridge to prevent plugs being transposed.

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Valeo Suspension Hydractive ASC
73807802 - 12v - 13.90
H2 S2001
Smooth Die Cast Alloy Case painted Black with thin pressed steel lid.
Has a White 15 pin connector and a Black 15 pin connector. White connector as above. Black connector has an internal polarisation ridge.

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Valeo Suspension Hydractive ASC
73807802 - 12v - 51.90
H2B S2001
Case and connectors as H2 above.

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Valeo Suspension Hydractive ASC
73809602 - 12v - 40.91
H3 S2001
Case smooth die cast alloy unpainted with thin pressed steel lid.
Connectors as H2 above but White connector has added internal polarisation ridge.

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Mk2 XM types

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Valeo
73810802
9610493180 - 12v - 22.94
H4 S2G2G
Case finned Die cast alloy unpainted with die cast alloy lid and high quality weather seal.
Connectors as H3 above but their position is transposed on the PCB.

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Will see what I can find to add to this list as I get the chance.

John

steelcityuk · Post by **steelcityuk** » 15 May 2009, 11:16

Just to add to this discussion (mainly for newcomers to the joys of Hydractive suspension), it's worth bearing in mind that the electrical side is just the trigger for the 'soft' setting. If you have low system pressure due to a worn regulator or a faulty valve then even though the ECU thinks it's in 'soft' mode hydraulically the car could be in 'sport' mode.

Here's what I found when I dismantled the Electrovalve on my Xantia. The green 'string' is a broken O ring.

Steve.

DickieG · Post by **DickieG** » 16 May 2009, 09:20

The following photo taken of the ECU from my estate helps make some sense of what a VN05N looks like, the blown one is circled (notice the burn marks where its been overheated) with the spare slot used by Activa's below.

addo · Post by **addo** » 16 May 2009, 10:00

Look at the solder eyelets. That's got seriously warm!

MikeT · Post by **MikeT** » 16 May 2009, 11:12

This is interesting.
It looks like they've been de-soldered. Is it a case of the heat wicking the solder up the leg(s)? Why hasn't the second one suffered the same?

xmexclusive · Post by **xmexclusive** » 16 May 2009, 11:47

Hi DickieG

Thanks for that. Did you happen to make a note of the case markings?
There are a lot of differences compared to the H4 that I have opened. The VN05N's are positioned the otherway round with the metal tags soldered to an extra bit of pcb. It uses the same TI microcontroller though. There is no real sign of any heat sinking to the VN05N's so the circuit designer did not expect them to run hot enough to go out of spec. I shall be interested in what I find in the older Mk1 XM ECU's as I do not think the VN05N's were about then. If so they just might use discrete electronics to drive the electro valves. Now that would be an intesting bit of circuitry to get documented. Anyone know if Mk1 XM's have the same electrovalve driver problems or are they trouble free?
Will see if I can take and post photos of the ECU's I open so we build up a searchable record for the future. If anyone is throwing away dead or unwanted ECU's throw them my way please and I will put them into the pile for opening and recording.

John

DickieG · Post by **DickieG** » 16 May 2009, 11:47

MikeT wrote:This is interesting.
It looks like they've been de-soldered. Is it a case of the heat wicking the solder up the leg(s)? Why hasn't the second one suffered the same?

I can't recall where the solder went to TBH, each VN05N operates its own Hydractive block. IIRC the top one is for the front block, bottom for the rear.

Mandrake · Post by **Mandrake** » 19 May 2009, 08:52

Hi All,

Good to see people still persuing this one, it's definitely not a myth

It does sound like there is a difference between Xantia and XM though - at least the early models.

As far as I know, the S1 Xantia's all have diodes in the Electrovalve's, but it wouldn't surprise me if the early XM's put the diodes in the ECU and they later moved the diodes to the electrovalve - as Jim points out as close as possible to the coil is best for absorbing the back EMF as the inductance of the wiring to the electrovalves would be not inconsiderable - and the reason for moving them close to the coil would probably be for EMI reduction to minimize interference to the car radio.

In terms of whether the electrovalve will actually function though, it doesn't make a lot of difference which end of the cable the diode is at, ideally there should be one at both ends - one in the electovalve to minimize EMI, and one in the ECU as a backup to ensure protection of the switching device (Does anyone know what it is ? MosFet ? Bipolar ?) in the event of failure of the remote diode.

Peter.N. wrote:Fitting the diodes will under most circumstances restore the ECU operation but the fault conditions when, presumably the diodes in the chip have failed are interesting. On opening a door you hear the solonoids 'clonk' and the whine as normal but no soft mode, when the electrovalves switch off again - no sound but on one occaision the suspension dropped and it depressurised the centre sphere! something I have been trying to do since I have been running them. I know because I changed it.

I think that what is happening is that the initial 12v pulse is opening the valve but the pulsed signal is not providing enough current to keep the valve open, so it is possibly sitting somewhere between the open and closed position. Fitting a couple of diodes on the board rectified the situation.

Your thoughts?

Peter

That's exactly what's happening - the initial 12v pulse will switch the electrovalve on even when the diode(s) are faulty but then it will drop out again after half a second when the 1Khz square wave is supposed to appear.

There are two different symptoms that can happen at this point - one is that the square wave continues to be produced (you hear it whining, albeit slightly differently to normal) but the electrovalve still drops out, the other is that the ECU will detect a fault and shut off the output completely.

In the former case my suspicion based on my own faulty electrovalve is that the diode itself was not faulty (not an open circuit junction) but rather that there was a dry soldered joint betwen the diode and the rest of the circuit inside the plastic moulding - on mine the fault would come and go gradually with temperature and got worse as it got hot.

With a high resistance dry joint the ECU still seems to keep outputting the square wave but the electrovalve doesn't energize properly and drops out. The other electrovalve at the other end of the car is unaffected.

If the diode goes completely open circuit the symptoms are a bit different - the ECU detects a fault condition and shuts down the output for one minute - BOTH outputs to front and rear. So a fault on one electrovalve in this way will cause both electrovalves to shut off and remain in hard mode even though only one is faulty.

(You'll also notice this behaviour if you disconnect one electrovalve - the other end of the car will go hard too)

After one minute the ECU will reset and try again - a half second pulse of 12v then a square wave again, if the fault is still present it will shut down for another minute.

By the way, this automatic shutdown/protection mechanism does NOT work if you have an LED/resistor combination connected to the same output as a faulty electrovalve, as the load of the LED, as small as it is, is enough to trick the ECU into thinking everything is fine, even if the electrovalve is faulty or disconnected...

Regards,
Simon

xmexclusive · Post by **xmexclusive** » 19 May 2009, 12:42

Hi Simon

Thanks for that bit of information.

Somewhere I think I have the full manufactures specification for the VN05N's. Found it when I was sourcing my supply of them. Someone from Australia provided a supplier "MOUSER" in the USA. Cannot credit him as all that info is now tied up in the demise of Club-XM.com. The VN05N's are described as "Solid State Relays", will look and see if I took a hard copy. To add confusion there is also a general purpose 3 pin MOSFET IC that goes under the name of VN05 which many UK suppliers stock.

I have now cracked open the 4 MK1 XM suspension ECU's and these have no VN05N's in them so will probe for the electrovalve driver circuitry when I get the chance. These look to have the generic PCB that Jim predicted and are built around a Motorola 6805 microprocessor.

John

KevMayer · Post by **KevMayer** » 01 Sep 2009, 13:47

A question for Steelcityuk.

I've just stripped down my front electrovalve to stretch the small spring. I found the O ring to be broken like the one in your picture above.

Did you replace the O ring?

I need a new O ring but can any normal rubber O ring be used or does it have to be special rubber?

For now, I've managed to super glue the old O ring.

I can't tell what this O ring does. Does anyone know if it's critical?

It's the O ring on the right in the picture of the electrovalve body below.

Post by **CitroJim** » 01 Sep 2009, 14:57

The O ring, as far as I can tell, seals the two halves of the electrovalve. If it's duff, you'll have leakage out of the top of it around the 16mm hex and it'll cause all sorts of problems in soft mode, similar to my issues, not least a big mess and a fast tick. The valve body has system pressure in it when in soft mode so that O ring is critical!

Any LHM-proof O ring should be OK there. Test any suitable ones by soaking in LHM for a day or so to see if they deteriorate. If obtaining one is tricky, have a natter with Martin at Pleiades.

Kev, on another related subject, did you have much difficulty removing your electrovalves from the sphere blocks? I ask as most I've tried to remove from sphere blocks by trying to undo the 16mm hex at the top have resulted in the valve itself separating and leaving the valve body firmly in the sphere block. I can see no way of getting anything sensible on the 24mm hex at the base of the valve to undo it unless you separate the valve, remove the coil and use a deep 24mm socket on it.

Did you replace the green O rings when you've had valves out or did you chance re-using them or indeed, did you do all maintenance on them by leaving the main body screwed into the valve block?

KevMayer · Post by **KevMayer** » 01 Sep 2009, 16:53

Hello Jim,

I removed the electrovalves by putting the hydractive block into a vice and used a 16mm spark plug socket on the top 16mm return pipe hex.

The whole electrovalve came off in both cases (front and rear). I then used a 24mm ring spanner on the body and the same 16mm socket on the top and opened the valve up.

The first time I did the rear I baked the electrovalve at 75 deg C for 15 mins before I opened it up.

On the front valve I just opened it up without baking.

I had the rear off a second time and the whole valve came off the block again as one piece just by using the 16mm socket on the top.

The O rings on the rear were all ok so I didn't change them.

The O ring on the front was replaced with a standard rubber O ring.

I bought an O ring kit, so, I'll put one in LHM to see if it's up to the job.

I can't see the O ring listed as a separate item so if my black rubber one doesn't work, I'm not sure where I'll get a new one ?

FrenchLeave · Post by **FrenchLeave** » 01 Sep 2009, 17:43

I'm embarrassed to appear in this exalted company, but I don't think LHM has any peculiar properties other than being mineral-based. So any mineral O ring will be satisfactory provided the dimensions are correct.

Derek

Post by **CitroJim** » 01 Sep 2009, 17:53

Hi Derek,

Well, yes, LHM is a mineral oil but by golly can it eat the wrong sort of rubber for breakfast

Spill some on the sound deadedning panels on the floor pans and it'll turn it to a mushy mess! I know from a leaky dosuer valve once

All rubber in LHM systems is specially LHM-proof. Indeed that was the problem of putting LHM in an old pre-66 DS that was designed for LHS2; it would eat the seals!

Kev,

Sorry! I could not see the O ring in the picture as I was at work and our corporate system does not display pictures so I guessed. I thought you meant the black O ring between the two halves of the valve body. The one you indicate will have the effect of putting the car into a hard/soft limbo mode when hard is selected. It might be very comfy like that! In fact it is likely it'll be soft all the time irrespective of what the ECU says...

Thanks for all the valve removal tips Kev. I'm going to try doing it with the sphere blocks in place. I have swapped one sphere block at the rear and it's a heck of a job. Access to the valves (on the V6) are reasonable so it'll save needlessly disturbing other seals.

KevMayer · Post by **KevMayer** » 01 Sep 2009, 21:20

Just finished working on my front electrovalve again.

The black rubber O ring I fitted was obviously the wrong grade of rubber. The original O ring is quite hard and I can now see why. It needs to be hard to withstand the full hydraulic pressure which is applied across it in hard mode (electrovalve de energised).

My replacement O ring was too soft and couldn't hold the pressure. What I found was that when I switched the engine off and closed the doors I could hear the electrovalves buzzing for their 30 second routine but, at the final click to off (and hence to hard mode) I could hear a loud hissing sound as my accumulator was depressurised (presumably down to about 80 bar at which the security valve would hopefully shut).

All I could think was that the pressure was leaking through the front electrovalve. There were two possibilites, either the O ring was passing, or the needle wasn't sitting in the seat to blank off the pressure feed.

I tried running the engine with the front valve plug disconnected to try to confirm the problem. The front valve hence in permanent hard mode. Like this the rear wouldn't change to soft. There must have been too much leak through the front valve.

I took the front valve off again and refitted the original O ring which i'd superglued earlier today as a desperate attempt to get it running.

Once it was all back together I started the engine and did a few rounds of citaerobics and then tried the front and rear. They were both in soft mode. I turned off and waited for 30 secs until the valves closed. Waiting to see if the hissing sound was still there. No hissing. I opened a door and tried the front and rear. They'd both switched to soft mode. I shut the door. 30 secs later both ends were hard. I opened another door and both ends switched to soft.

My superglued O ring will have to do until I can get a new one. It seems to be working fine for now.