Another EAS chestnut, I'm afraid. I have searched on many forums, and copied and printed much advice, to form my own EAS rescue pack, but I am still stymied.

Whilst driving, the car would almost always (except for the MOT journey!) jump to extended height. The next morning, when switching on, the ECU would recognise the error, and lower to normal height, only for the blasted thing to jump up within a mile. I suspected the height sensors.

I have renewed all four height sensors, and nanocom reports height values within three bits side to side - so OK so far.
The compressor will charge the reservoir to 10 bar within several minutes, and hold that for up to a fortnight, until I switch on, when all pressure is lost.
I have very carefully replaced all the seals in the valve block, and soldered all the wiring in the passenger footwell.
I have replaced both the ECU and the driver pack with used "known working" parts, with no change in behaviour.
I cannot think of anything else to check.

Nanocom reports no faults, and appears to read correctly all data from the ECU
However, when reading the valve settings, it shows both rear valves open, and fronts closed initially - OK - but both inlet and exhaust valves open - surely wrong?
What can this mean, and what might be the remedy? I would be very grateful for an insight since I have tried everything I can think of.

Have you checked that the silencer on the valve body is flowing air?
Mine would also lift itself to extended height occasionally and not lower, it turned out to be a clogged silencer. This does not explain all your symptoms but might be a good starting point?

My first instinct says driver pack or ECU but you've replaced both. Did you replace both at the same time or one and then the other?
I'm wondering if a faulty ECU might damage the driver pack or vice-versa.

Can you use the Nanocom to actuate the individual valves in the valvebody? When attempting to find why mine would lift itself to extended height I used my Faultmate to actuate individual valves, and I could hear them switching, but the exhaust valve seemed to have no effect which lead me to the clogged silencer. Perhaps a similar test on yours might show where your issue lies, or give more clues.

Clogged silencer would definitely do it as it wouldn't allow air out when it needs to. You can unscrew it and leave it off to test, it won't do any harm but you will find out why it is there. When it exhausts air, you'll certainly hear it.

That wouldn't explain it losing all pressure from the reservoir when you switch it on though. When changing height, it will always open the rears first then the fronts once the rear is up to height to prevent your headlights dazzling people when changing height. Quite why the Nanocom is reporting both inlet and exhaust as open at the same time though is a bit weird.

Thank you, gentlemen, for your prompt responses.

I have been running, when it worked, with the exhaust silencer off, and the occasional gasp of air did not trouble me at all.
I was aware of rears rising first on inflation, as stated above, so the nanocom reports that correctly. So why report both inlet and exhaust open at the same time?
I first replaced the ECU, and when this had no effect, I replaced the driver pack.
Unfortunately, the nanocom will not open individual valves, but only command a change of height, as well as reading / calibrating height sensors etc.
However, with the valve pack on the bench, and also in the car, by applying 12v to the appropriate pins in the disconnected C152 connector, I can activate all the valves, and hear them clicking - driver pack OK ??

What I failed to mention in my original post earlier, was that fully serviced, tested and reassembled, it is sitting on its bump stops - full tank of air, ride height sensors in range - and when I switch on the ignition all the air is lost.
This has me completely mystified

Nanocom can open individual valves, I do it all the time if I want to lift a car to get underneath without running the engine. Go to the outputs screen and you open any one of the corner valves, then scroll to the next screen and open either inlet or exhaust. So if I want to lift or lower the front of the car while working on it, on the first screen tap open front left and front right, go to the next screen and tap on open inlet or exhaust and then tap close all when it is at the height I want it. If there isn't enough air in the reservoir on the next screen you can turn the compressor on or off.

Christopher wrote:

What I failed to mention in my original post earlier, was that fully serviced, tested and reassembled, it is sitting on its bump stops - full tank of air, ride height sensors in range - and when I switch on the ignition all the air is lost.
This has me completely mystified

So your saying you turn on the ignition, and it dumps the entire tank out the exhaust port?

Has the car always done this since you bought it ? If so, I would check the wire colours in the connectors in case somebody has been messing with them.

When checking with 12V on C152, apart from clicking how are you checking the correct valve opens ? Easiest way is to unscrew the solenoid tops, but leave them in place. Then when applying 12V, lift the solenoid off & check it was that one operating.

With the Inlet & Exhaust open at same time it will dump tank air out the exhaust, unless the diaphragm is on. As soon as the pump kicks in, it should close the diaphragm preventing air escaping even with both In & Ex open.

One other thing that causes random extended height while driving, is intermittent connections on the driver pack connector. Changing driver packs doesn't help, because the issue is loose socket contacts. The fix is to carefully remove each socket contact (one at a time), and gently squeeze them to get a better connection on the pins.

The reason for extended height, is because the dumb ECU fails to see height changes when opening valves, and initially assumes the chassis is grounded. Mine does this, but as long as I spot the flashing height switch in time & press down it's ok. If I miss the flashing, it will go over extended, and go into soft-fault mode. Ignition off-on will resolve it . . . .BUT . . . if I cannot stop & do that, it will eventually go fully faulted & require Nanocom reset.