I don't think the delay in raising this morning was a leak. It had been running with doors open for a while then nothing happened when I shut the doors. As soon as I pressed the 'raise' rocker switch it shot up. Mark's suggestion about the system being in 'pause' mode and needing a switch pressed to un-pause it makes sense.

I don't really think I'm going to know much more until I look at these height sensors. Next job ...... In the mean time I've ordered a card for the Nanocom to record live readings.
Patience young padawan. Hang on in there ;)
 
Assuming no leaks, with engine running & door open, the pump should run and fill the tank until the pressure switch triggers. Also the height switch should be lit but not flashing. Then when the tank is full, closing all doors & tailgate allows the system to adjust. Occasionally the height switch will not change state to flashing (adjusting), but I never figured out exactly why this happens.

Quick check on the height sensors is to set each height manually (Access, Motorway, Normal & High Mode), and note the readings for each. If any are wildly out from the expected values then you might have a height sensor issue, but unless the tracks are dirty & housing is leaky then you're probably ok. As said earlier, gently moving the sensor & watching for jumpy readings is the proper way.

If the system still hunts up & down with the car level & parked, you still have leaks somewhere, either in the pipework & joints, or inside the valve block. Given that you have one of Kurt's valve blocks the Seals, Valves & NRV's should all be good & prevent internal leaks.

Mine does hunt up & down a bit when stationary, mostly at rear, but in my case there is a small leak through the Inlet & Rear valves inside the block. This causes the rear to rise slowly between each ECU adjust cycle, but only about half inch. Not noticeable while driving though.
 
Since it stops when door is open, as it should, then the system must be being told to do stuff so again I reckon sensors. If one sensor is not playing nice then it will hunt and as it does so it upsets the other sensors which were correct, so they then start jumping around trying to make sense of the chaos. You then have the wee Kirkcudbright Centipede
 
And once again, thanks everyone for your ideas. Padawan, mmm, I think that that might be rather generous. I'm more at home with 1950s and 60s tractors. No suspension, no electronics and built to last.
Anyway, the height sensors are my next line of attack.
Cheers and Happy New Year to all.
 

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