Started a week ago. Operates fine when driving but compressor's been having to run quite frequently it seems. I reckon it's something to do with the valves. The main block was replaced at the main dealer last year. Does this one also have a secondary block just for the front?

 

Subscribed.
I went through the “aged” workshop manual that I have. Other than the description and maintenance of the airspring, there is nothing about the air system. Hoping someone has those necessary pages.
When this particular situation occurred on my xjr, the front block was to blame.
According to this source (valid?), it looks similar.
https://www.expedition-parts.de/en/l...esonderheiten/

 

if just the front drops, i would recomend pulling the EAS fuse and let it sit overnight. Iff both sides drop, suspect the valave block [there is only one for front (right front behind wheel well inner cover)] or possible leaking voss fitting and/or leaking pipe. If one side drops, suspect the air bag on that side and/or leaking voss fitting or pipe to that air strut

as for the valve blocks, there are three total. one by the compressor, one for the front and one for the rear

 

Yes, just the front drops (left & right). Where's the front block located?

 

it is behind the front right wheel well inner cover. It is just behind the front bumper area. You will need to remove the clips holding the front part of the wheel well inner liner and pull it back to access the front block

 

Sorry @jahummer , I forgot I had this...