Recently my SLS compressor has cycled +/- 3 times immediately after turning the engine off. The cycles are about 1 second on / 1 second off. The sound is identical to the sound / cycle made if I use a Nanocom to test cycle the compressor in the driveway with the engine off.

Question 1: This hasn't always occurred, why is it happening now?
Question 2: The SLS system seems to move up and down pretty frequently whilst driving around town. I replaced the bags about a month ago and everything else functions normally (eg. load up with 6 people, no problem. Leave for a week - no leaks). Shouldn't there be some sort of lag circuit - so that the computer adjusts the height only if the position has changed for 10, 15, 30, ?? seconds?

Best,
Andrew

That's a SLABS ECU missbehaviour, it happens but it's not normal, the only normal thing for the SLS is to lower a bit after the ignition was off and load removed from the vehicle.. the compressor is not supposed to work with ignitiion off whatsoever... even if it happens quite often... you'll not like that but unfortunately the only cure is to replace the ECU

Mine occasionally makes that noise and has done for 9 years. The only problem was when the relay welded its contacts together so I had to remove the fusible link to stop it!

Mine also adjusts the height sometimes when stopped at lights etc if there is an appreciable side slope. Again, I don't worry about it. I have an LED fitted to see when the compressor is on.

As Fery says, there's always a "sigh" when I unload the back - eg people getting out, stuff out of the boot. The compressor usually comes on for a short while when I start up again.

To close this loop:
I replaced the suspension bags, as advised, to address the occasional 'sinking'. This was not very difficult and has addressed the problem. The SLS pump still activates, rarely (perhaps a couple times per month?), after the key is turned off. I've learned to accept that which I cannot change - and does not cause any further faults
Regarding a 'bag' change:
- Most time consuming / difficult part is getting the tail sufficiently high in the air with the jack and stands I have available. Your Landie has a lot of suspension travel, and it's all got be let out to get the bags free.
- Bags do explode (supposedly), but mine had an intermittent / unpredictable failure. They appear to be two layers thick (when cut open) and I suspect that the holes need to be aligned just so to result in a leak.
- there's not much slack on the supply air line. Be frugal when you cut the old ferrule off - there doesn't appear to be too many replacements left on the line.
- do clean the supply line end completely. The new bag (a Continental?) came with a fitting-free connection. Presumably, the supply line needs to be round, clean, with an nicely squared end to work correctly. Mine did - but I was a bit worried.

Thanks to the board for the input.
Andrew