Wow, a lot of confusing and some conflicting results here, I'll see if I can make any sense of it....
steelcityuk wrote:So I finally refitted the rear HA block and electrovalve onto the Xantia, as the weather was nice I decided to remove, strip and clean the rear HC as well. I was surprised just how much dirty LHM came out the thing, I've only recently flushed and replaced the fluid in the system. Anyhow by Friday evening it was all back together. No difference to the ride whatsoever. That said the regulator cycle time was still 6 or 7 seconds so it wasn't surprising.
Yeah cleaning the height corrector wont have much direct effect on the ride, unless it was so chocka with crap that it couldn't maintain the correct ride height.
Usually when they get sludge in them they just get very slow at responding to height changes - it might take 15 or 20 seconds instead of the usual 5 seconds to respond to a change in height. It's good to clean them out though, I've done both of mine...
Yesterday I removed the regulator and stripped it, what a complete pain it was to remove the spring clip holding in the single bolt mounting end, it took an hour just to remove this.
Yikes... I hope you were careful, and forewarned of the dangers of that spring during disassembly.
Everything looked OK but I think like the pump it's been replaced by a previously enjoyed one. In a moment of boredom/desperation I decided to shim it up to increase it's pressure. I had no idea what sort of pressures the regulator was cutting in and out at - I haven't got my gauge sorted yet. I found some repair washers in the local B&Q that I could modify to fit, based on the XM forums postings adding a 0.1mm equals 1 bar increase so these shims I've added have increased the regulator pressures by 10 bar. So both cut in and out are now 10 bar higher than they were. I also reseated the ball bearing with a brass bolt. I was full of hope that this would be the magic fix...
Yep, its 1 bar per 0.1mm according to my book. Normal pressures are 170 +/- 5 bars for cut out and 145 +/- 5 bars for cut in, so the pressure being 10 bars higher than normal is not going to hurt anything...
So I got it all back together and went for a spin. No different, still harsh.
However whilst sat at the lights I found that if I blipped the throttle I could hear a faint clunk as the LED indicated a switch into hard mode, never heard that before.
Yes, thats normal, if you blip the throttle at the lights, the electrovalves are noisy enough that you can hear them switch at idle. (But not while driving)
What you probably don't know, is that will only happen AFTER you have driven somewhere since turning on the key. EG if you start the engine and start blipping the throttle, it won't do anything.
But if you then back out of your garage and then drive back in again you'll find that blipping the throttle WILL have an effect... basically reading the throttle sensor is not activated until the ECU detects some minimum road speed since the last reset. (This is described somewhere in the HA2 training manual...)
Back home with the car ticking over I found that if I changed the height and blipped the throttle the clunk was accompanied with a small jump in height, this I thought would be as the extra spheres were switched in and out. So somethings changed.
Ok, so what you're saying is the car is idling at normal height, the LED is on, then you change the height a bit, blip the throttle (causing the LED to go off then on again, as it should) and that causes a jump in the height ?
That sounds suspicious.... it sounds like you might have faulty diodes in one or both electrovalves.
What happens normally is this - the ECU provides 12v DC for half a second every time it switches from hard to soft, and then it drops back to a pulse width modulated signal at 1Khz with a peak voltage of 12v and average of about 3v. (You should notice your LED initially comes on bright, and then goes slightly dimmer, depending on what resistor value you used)
This is because 3v is not enough to switch the electrovalve on, but 12v is too much dissipation in the coil for long term running, so it pulses it to get it to switch, and then drops back to a lower voltage which is enough to hold it in without overheating.
Inside the coil sleve is a reverse connected (back EMF) diode just like you would have across a relay coil, and without this diode the electrovalve will switch on when it gets the initial full 12v DC, but will drop out again half a second later when the ECU drops back to the pulse modulation.
So the result is that the suspension is actually in hard mode all the time EXCEPT for half a second when the ECU is switching from hard to soft. So you change height but because the centre sphere is closed off the pressure can't equalize - when you blip the throttle the electrovalve opens for half a second, the pressure equalizes (and causes a jump in height) and then it goes back to hard mode again.
See my message about half way down this thread:
http://www.frenchcarforum.co.uk/forum/v ... 3&start=15
Can anyone else hear their HA valves move when they blip the throttle?
Following this I decided to check the cycle time of the regulator, so with the bonnet open I sat on the slam panel, sure enough as the car adjusted it's height the regulator clicked a couple of times then stopped, after 7 minutes of waiting I got bored of waiting and thought it's either very good or very bad. I got off the panel, the front dropped down again, I sat on the panel again which prompted a couple of regulator cycles as it rose then nothing again. Is this an excessively long cycle time?
Not really...the fact that the regulator cycles at all when the car standing is only due to slight leakage in the system from the various units which are connected to the high pressure supply (height correctors, brake doseur, electrovalves to name a few) and when the leakage is very low you can get very long cycle times.
When I first replaced my leaky electrovalve the cycle time went up to nearly 5 minutes... but it is a lot lower than that now, about a minute.
Next I thought I'd check the firmness of the suspension with the engine running, nice and soft at the front but the back seemed a little firm which was strange because as I accelerated on my 'test drive' the back was dipping quite a lot. So I stopped the engine closed the doors and checked again, same as with the engine running, soft at the front and firm at the back. After the time out the car went into hard mode (confirmed by the LED) I checked again, very firm at the front and now very soft at the back! I didn't believe it so I opened a door and checked again. Sure enough in soft mode the back was very firm and after the 30 second time out very soft! So I think that either the pipes to the rear HA valve are mixed up or the internals of the valve are wrong.
Well that is just totally bizare! I can't see any possible way that the hard/soft modes could get transposed like that, especially at just one end of the car. You're not opening the boot to sit in the boot are you ? The boot lid triggers the soft mode just like the side doors do.
There is no external piping that could get mixed up that would give those symptoms....
Is it still soft at the back with the Hydractive fuse removed ?
If you disassembled the block is it possible you reassembled it incorrectly ? (Can the main slide valve be accidentally reversed inside ? I've never taken the main block apart before....)
Regards,
Simon
