(Another) EAS Fault

Hi Folks

I’ve been trying to self diagnose a fault with the infamous electronic air suspension on my 2016 D4.

This thread (https://www.landyzone.co.uk/land-rover/suspension-compressor-runs-constantly.324380/page-2) has been a great source of help but I’ve not been able to pin point the fault and I’m reluctant to fire the parts cannon at it so came seeking some advice.

I’ve got an AMK compressor with the following fault:

C1A20-64 (6C) Pressure increases too slow when filling reservoir - Algorithm based failure - signal plausibility failure.

Symptoms started and persist with the front of the car being very slow to raise on both sides. So much so the compressor hits it thermal cut out, cools and then restarts. Logically then, I’m looking at compressor, valve blocks, lines leaking or both front bags which would be somewhat coincidental.

I’ve overhauled the compressor/drier and seals, as well as the front and centre valve block seals but to no avail. I’ve leak “tested” the feed to the gallery (reservoir) with soapy water and no obvious leaks.

My thought process at the moment is that air is escaping somewhere causing the compressor to overwork and overheat. But this is at odds with having replaced the seals.

My latest attempt to diagnose the issue is having pulled F26, the below screenshots are 12 hours apart - it would suggest then the front valve block or both bags. Both of which seem unlikely given overhauling the block seals.

Has anyone any suggestions? I’ve IID and have been monitoring gallery pressure and it’s within limits. To note the rear of the car raises first, and very quickly; and my driveway is on an incline which is why the figures below are not equal.

Any help much appreciated!

Hi

The air tank can leak on top where u can’t see it , , did u pressure tested it on its own plse , alas there is a seam on the top where u can’t see it , I disconnected it and made up a test kit and left it over 12 x hours using a pressure gauge etc m found it was dropping ,

what are the heights in mm set in normal ride height plse , measure from the centre of the wheels to the bottom of the wheel arch liners , the rear is suppose to raise first, that’s to prevent glare from the headlights

Enclosed a pressure sheet for u so u can see what the compressor should be producing ,

Another thing is it might leak from the air bags but only on different heights , so see how u get on in normal or off road height settings

Plus did u happen to fit a new amk exhaust valve as they can sometimes let by , but at the end of the day ur compressor might be worn out, know it can be frustrating but best to go through the system step by step

Hope that helps and as u have the gap iid will be easy to monitor the live data of what the system is doing

Another things is when u removed the dryer material from the compressor did u ensure the filters inside where clean and wasn’t blocked at the far inside of the dryer chamber

The exhaust valve on the amk can also fail and let by

There’s also an inlet air filter inside the side boot locker , need to ensure the compressor is able to pull air in otherwise ur basically pulling a vacuum if it’s blocked

But using the gap live data ur soon see what kind of pressure the compressor is making

Hope that gives u a starting point

gstuart said:

Another things is when u removed the dryer material from the compressor did u ensure the filters inside where clean and wasn’t blocked at the far inside of the dryer chamber

The exhaust valve on the amk can also fail and let by

There’s also an inlet air filter inside the side boot locker , need to ensure the compressor is able to pull air in otherwise ur basically pulling a vacuum if it’s blocked

But using the gap live data ur soon see what kind of pressure the compressor is making

Hope that gives u a starting point

Click to expand...

Thanks Stuart, really appreciate the guidance and help on this - tying myself up in knots as I am not familiar with the order of operations for the system. The front raising last certainly makes logical sense now.

I've replaced the filter material at each end of the dryer along with the granules (kits from 4x4 Airseals). I've also checked the intake filter, and even tested the system without the intake filters in just to rule them out. The reservoir pressures appear nominal with that chart both under load and residual, albeit it increases slowly 1 kPa at a time; i'm not sure if this is normal of indicative of a compressor on its way out. The screenshots above are having left the car at ride height overnight.

I'll be sure to drop the reservoir and check it this evening and report back as well as measuring the the ride height.

I'm assuming the capacity of the rear bags consumes the stored pressure in the reservoir via the central valve block and then the rear valve block, and then the compressor has to make up the rest in terms of the order of operation?