Been troubleshooting my EAS fault and finally got around to performing the "drop test". Parked the LR3, pulled the fuses, measure the distance between the top of the center cap and the fender, let it sit overnight and remeasured this morning (12 hours later). Results below:

FL - 5/8" drop
FR - 1/4" drop

RL - 1" drop
RR - 7/8" drop

Not sure what the "normal" drop should be overnight but these measurements seem to indicate a couple of things to me:

No one corner shows any significant drop.
Rear dropped more than the front but not significantly
Although the left dropped more than the right it started higher as well so this could indicate a normalization

Depending on what a "normal" drop should be this tells me I likely have something going on with the compressor (still) as I just rebuilt it or with the front back distribution or with the rear distribution.

Any comments or additional thoughts from the community?

Thanks in advance!

 

No amount of drop is normal. Each strut is isolated by a suspension valve that can only let air in or out when energized, hence the reason we pull the fuses. Taking power away prevents the computer from waking up and making adjustments, which means each strut should maintain its pressure in turn, keeping the same height.

The results of your test are inconclusive. I would have to theorize that you either didn't pull the correct fuses (I usually just pull the battery cable) or all your valves or all your air springs are leaking, or a combination of that.

 

I definitely agree with the above comments.

To make it even more difficult, if three of the wheels were perfect and just one leaking, then it is possible to have one corner higher in the morning.

There can be a certain amount of cooling overnight that could lower all four air springs a small amount but your situation sounds like various small leaks thru out or the auto level circuit was still in operation.

I assume the 20 amp fuse you pulled was F26E in the engine compartment?

Removing F26E should pretty much depower the computers and effectively shut the air system down.

DISCO3.CO.UK Photo Gallery - LR3 Air Suspension fuse 35P ECU Manual Shut Off Switch

 

Thanks guys. Pretty sure I pulled all of the EAS related breakers and fuses but I'll retest again overnight.

 

Re: the comment about not having pulled all the fuses.

you should be pulling these fuses to be on the safe side (or disconnect battery as was mentioned).

F26E (engine)
F3E (engine)
F35P (glovebox)

 

I've never pulled 35P before. What does that one do specifically?

 

AFAIK it (F35P) with the F26E covers the electrical controllers for the air suspension. I read a while back on another forum that pulling it along with the other two is the more failproof method of disabling the system.

I've pulled those three every time I needed to work on anything in that area, never had the truck move on me at all. Have pulled it for several mechanics when they were afraid to work on the truck as well.

EDIT: walked out of the office to check the manual, it lists 35P as "Air suspension ECU"

 

Ah, OK. I did not pull F35P when I performed the test (was going off a forum post about how to perform the test and it only mentioned F26E and F3E).

Both my new AMK compressor and a test tool arrived today...so I'll get crack-o-lacking on this thing, starting with a re-test.

 

A few years back, at first I did not quite understand how the system worked and thought that removing Fuse 35P was the key to freezing the suspension computer.

I later determined that removing F26E in the engine compartment would kill the computer 24/7/365 and keep it dead. Removing F35P only put the computers to sleep while the engine is running; later when shut down, the zombies wake up and drop the 3 while parked. Removing F26E is pretty much equivalent to putting a stake to the heart and kills the suspension computer "good".

I do however have F35P on a switch inside the cabin as if I get a suspension fault while driving, I actuate the switch which is the same as pulling F35P without having to open the glove box. Opening the F35P circuit primarily keeps the system from perhaps dropping while the engine is running.

If going under the 3, yes, disconnect the battery - all else relies on computer logic or the lack of it - not good enough when you only have one pair of hands.

 

Both the diagnostic tool and the new compressor arrived today. Pulled the codes and got C1A20 - Pressure increase too slow when filling reservoir.

Since I just rebuilt the Hitachi compressor (Piston sleeve and new filters and desiccant) I googled the code and found an interesting article on DISCO3.CO.UK about cracks in the drier cover. I'll check that first but if that's not the issue I'll replace with the shiny new AMK.