Xm 2.0 Tct Exclusive Lpg, What's it like?

[DerekW]

Hi Steve,

Forgive me if I've misunderstood you, but switching between "Sport" and "Normal" shouldn't make any difference with the Hydractive 2 system fitted to your cars. If the 2TCT front end goes hard when switching to sport there's something wrong.

Derek

This post has been edited by DerekW on February 09, 2009 06:48 pm

[steelcityuk]

Hi,

I've not been flashed by other road users yet so either they are set relatively low, don't scatter too much (could be down to the complex reflector?) or other road users can't be bothered. I hope it's not the last.

I'm not using the switch to change the suspension setup, I'm aware that all that does is alter the parameters that the ECU uses to determine whether to use normal or sport mode (unlike Hydractive 1 systems). There's definately a fault with the Hydractive 2 system, the Lexia says it's soft and it is at the front but not at the back. Here's what I'm basing it on - When opening a door the ECU will switch into soft mode (unless faulty) to even out the sphere pressures. 30 seconds after closing the last door (with the engine off) the ECU disables the hydractive electrovalves to save flattening the battery (the whine stops followed by a click). During this 30 seconds it's possible to try a 'bounce' test to see how soft the suspension is, after the click of the hydractive system the car should move far less whereas on mine it doesn't change at the rear whereas the front does.

I'm itching to get the exhaust off and checkout the hydractive sphere and valve block but this snow is really putting me off. Still there's a few dash lights to replace...

The hydraflush is already making a difference to the front struts, they're not sticky when changing heights.

Steve.

[Citroenmad]

You could have a fault with the front or the back ECU diodes, its not unheard of for just one end to fail. So it could be that?

Although it is probably the centre spheres, as you said.

The sunroof emergency tool, where should that be kept? And how is it used?

Ive never looked on the Xm, but on Xantias you pull the trim down where the interior light is and there is a handle and winder under there. Is the Xm the same?

[steelcityuk]

Hi,

You could be right about the diodes but I thought that if the diode went then the ECU would sense this and lock into hard mode. I've already bought some 4007 diodes to upgrade the ECU so that it'll be done as part of my standard service and fettling. Usually I like to add a LED to the scuttle panel so I can see if the ECU is doing what it should be.

The sunroof handle clips into the fusebox under the glove compartment.

Steve.

[Peter.N.]

I changed the ECU again, on my green one because the suspension at the front wouldn't go soft, the old ECU works perfectly in the black one so I can only assume that the recently replaced front centre sphere has failed - I would be surprised if it was anything else - I'll let you know!

[xmexclusive]

Hi All

Sunroof manual handle is usually in the main fuse box lid except on some Mk1 model's where it is stowed in the glove box. See any Mk1 Owners Handbook XM-GB-5001 to XM-GB-5004 except the launch year Handbook 020 GB 7-89 which does not mention a sunroof at all.

John

This post has been edited by xmexclusive on February 10, 2009 07:31 pm

[Citroenmad]

Thanks, can't say ive had much of a look in there, other than putting my service book in there. Ill have a look next time i have the Xm out, see if i have one.

[robertmnorton]

Hi Steve, to clarify the function of the EV diodes, they are neither monitored by the ecu,nor do they support operation of the EV. Their failure results in damage to the output drivers for the ev's - the infamous VNO5's - sustained by the back emf generated during the collapse of the magnetic field which attemps to mantain current flow in the same direction.This back emf is shunted to ground in normal operation by the diodes - they act as a non return valve - when the VNO5 swiches off, preventing the current flow continuing.The failure of these diodes may not necessarily cause instant demise of the VN05's, but the damage will accumulate over time,maybe several months.If you can still hear the ev's buzz and click when using the door open/close scenario then it's likely all is well with the electronics/ev wiring.The only test we can perform on the ev are 1/ resistance of the coil - approx 4 Ohms, 2/check initial current flow of 3 Amps reducing to 1/2 Amp after 0.5s and that this value does not jump back up when the supply is swiched off.Just to bore you even more,old/stressed electical wiring can develop microfractures in the conductor and/or insulation causing intermittant failure and system operation, and of course as can corrosion/oxidation of contacts.

This post has been edited by robertmnorton on February 10, 2009 08:23 pm

[steelcityuk]

Due to a serious bout of cabin fever I removed the Hydractive ECU to fit the diodes. A quick check of the forums brought up several different methods of achieving the same thing. I decided to go for mounting them straight on the PCB pads next to the transistors. However on one of the PDF guides I looked at it seemed to be mounting a diode in the wrong place. It showed one diode above the other which if it was the same revision as my board is wrong because in that configuration the diode connects through the PCB tracks to the non existant transistor (would be for an activa?). Anyhow I traced the connections using a multimeter and on my board they are side by side.

I don't know if it's made any difference yet because I haven't taken the car out, some kind of bug has laid me low and it's minus 1 outside. My money is still on a hydraulic fault.

Steve.

[Dieselman]

What voltage do the solenoid valves operate on, is it 12v or something lower.?

If it's 12v and you can't reach a conclusion through the ECU, can't you just push 12v into the solenoid directly and check operation.

[Peter.N.]

There is a side effect of defective diodes, or at least there was in my case, which enables you to indentfy the problem just by listening. When you open a door and the solonoid opens the valve, you hear a 'clunk' followed by the whine, in a healthy system when the valve shuts the whine ceases followed by the 'clunk' as the valve shuts. On mine there was a clunk when it opened but not when it closed and the switching was ineffective.

What I believe was happening was that the initial current was opening the valve but the pulses were of insufficient amplitude to hold the valve open causing it to partially close. This theory has evidence in the form of depressurising of the centre sphere, something that I have never previously been able to achieve, each time I opened the door the suspension would 'jump' slightly and once 'broken' I was able to unscrew the sphere by hand.

I also have had a PCB of a different pattern which actually had three pairs of solder pads and like Steve I checked the correct connections with a meter.

Peter.N.

[xmexclusive]

Came across a technical note the other day that mentioned the introduction of the diodes in the electrovalves. The note stated that these diodes were added as a production modification during the 1998 model year. Replacement electrovalves supplied since then would also have diodes fitted and encapsulated in the valve assembly.

It seems that up till then the suspension system relied solely on two minature diodes built into the VN05N solid state relays.

John

[steelcityuk]

Dieselman,

The electrovalves are kicked into operation with a 12v pulse followed by a much lower 'maintenance' voltage that's a PWM voltage that creates the whine that is heard from the electrovalves. If 12v is put through the electrovalve coils for too long they heat up and burn out. If a LED (with suitable resistor - approx 1k Ohm) is wired onto the electrovalve supply circuit it's easy to see this as a bright flash followed by dimmer glow as the ECU switches into soft mode (assuming the system is working correctly).

Hope that explains it?

Steve.

[steelcityuk]

A photo of the dirty LHM filter.



And the LHM.



This post has been edited by steelcityuk on February 12, 2009 12:28 pm

[robertmnorton]

I have never seen the like of that gloop in my life with xm's or bx's.Looks like you've got a weekly drain and flush for a month or so.You need an ultra low viscosity cleaning fluid, to get high velocity flow rates.I would think a 50/50 premium paraffin to lhm would help,preferably at between 40 to 60c ,but probable removal of hyd components and disassembly in pure warm paraffin, though i have seen some cheap ultrasonic baths that could be "adapted.Happy times!