Unexplained SLS issue

[assafde]

As a general background after long experience with the vehicle SLS system, some components were replaced as a repair for knows issues.
It's a 2001 TD5 ES equipped with rear air springs and ACE system.
On March 2011 I had replaced BOTH rear air springs with the original Contitech brand + 2 hight sensors, hence they are in good condition.
Lately, on some field trips, she went down on both sides as it in transportation mode, still having air inside the springs about 1" above bump stops.
Turn off ignition, wait for an hour and car back on normal ride hight.
No shagging over night, solid rock.
While pressing the off-road mode switch, compressor start to work and stop right after ~ 10 sec, Off-road lamp blinking with no stop, car is not lifting in back.
Checked:
1) fuses - OK.
2) Fast link - OK.
3) Under hood solenoid (yellow) - replaced - OK.

We went into the testbook, and found "16.7 compressor duty cycle exceeded" which means, compressor does not function as new but can raise the car quickly.
We found it hard to believe, compressor is dying since on manual operation (via TestBook) it had lifted the car on a reasonable time.
Valve block were manually tested as well with the TestBook, as well the exhaust valve operate normally, lowering the rear end.
So far, ALL mechanical and electrical stuff, seems to be OK.

Using the TestBook we reloaded the SLABS ECU (it's a TestBook exchange procedure) "telling the main vehicle ECU we have a "new" SLABS.
after doing the the vehicle lit up 2 lamps:
1. Permanent Amber with up/down arrows (left lower corner on instrument panel).
2. Permanent Amber Off-road mode (right upper corner on instrument panel).

Clear all fault codes on SLABS restarting the vehicle we had the same lamps status.
Now, compressor keeps working lifting the car to normal hight, BUT Off-road lamp is on although car travel above 40Kmh, while above this speed, the Off-road should be automatically turned off.
ACE test procedures were all OK, not ACE system faults/failures, was funny to see vehicle lean from side to side only by a PC command...

SLABS was replaced by a main dealer here as a part of a recall procedure.
We suspect the SLABS as the faulty unit...
What do you think?

[Pedro_The_Swift]

Slabs doesnt fail very often,,
to have two fail is very odd.
I'd go with the compressor being a bit old and tired.

[assafde]

How can you explain the fact Off-road lamp on while passing 40kmh?
Compressor levels the car for normal hight, but cannot use the Off-roam mode, since lamp is permanent on (Amber upper right side on instrument panel).

[strangy]

You said Contitech air springs?
If these are from Armott, that will be the problem.

Otherwise based on your description, I would be checking the Earth points and wiring loom.

[alpick]

I had a seemingly inexplicable sagging rear end and went through checks of everything in the SLS system to find that in the end, it was the bags that was the leak. My research through the posts in this forum upheld the finding that in 99.9% of saggy SLS it is a bag problem.

http://www.aulro.com/afvb/discovery-2/133998-arnott-air-bag-failure.html.

http://www.aulro.com/afvb/discovery-2/119621-sls-sagged-morning.html

[stevo]

The compressor duty cycle exceeded is either a leak in the circuit or a tired compressor, this may have been the cause of the air bags going down when you were out in the field because when you go down any steep declines the air will drain out of the bags because the sensors think the vehicle height is high. the compressor could not keep up.

This is why I did a modification to mine by fitting a one way restrictor between compressor and the valves that control the air supply to the bags, when raising there is no restriction but lowering the vehicle there is a restriction so takes longer to lower vehicle less wear on compressor as for the lights that is a hard one but the fact that they came on after being plugged into the test book and reloading of the software may have been glitched.

[Pedro_The_Swift]

My last set from pommyland were Trelleborgs(:eek::eek:),, so far so good!

and as for off road height---
it takes around 70-80psi to raise a D2 to normal height,,

maybe thats your compressors max pressure?

[assafde]

Well, the issue is that the compressor does level the rear up to NORMAL hight.
Off-road cannot manually activated via the button inside the cabinet, physically it on normal hight, but electronically car "think" it's on active off-road mode.
While passing 40kmh, off-road does not turned off, not manually.

[assafde]

Ended up by replacing to a new compressor - all was back to normal operation

[OffTrack]

You said Contitech air springs?
If these are from Armott, that will be the problem.


Contitech are the OEM manufacturer for D2 airbags, nothing whatsoever to do with Arnott.

ContiTech AG ? Air Spring Systems (http://www.contitech.de/pages/contitech/organisation/organisation-airspring/organisation-airspring_en.html)

[alpick]

My set of Arnott springs had "contitech" imprinted on the rubber.

[e3j]

.......Turn off ignition, wait for an hour and car back on normal ride hight.
No shagging over night, solid rock........


Well there's yer problem right there......Get a good bed!

[OffTrack]

My set of Arnott springs had "contitech" imprinted on the rubber.

This was posted to another forum. Contitech were and are the supplier of the original D2 air bags. Perhaps Arnott uses bags made to a different spec? I don't know.

Land Rover Owner • View topic - Air springs (http://www.lro.com/forum3/viewtopic.php?f=63&t=67708&start=20)

...I also received a mail from Mark Griffin of Contitech.......interesting reading, here are some extracts.

"Dunlop airsprings on the other hand are a much smaller organisation in the sense that there is no longer a "Dunlop" of old in the market. Dunlop is just a brand name today and the brand is owned by many different companies."
"the Dunlop Airspring unit is a management buyout from Trelleborg 2 or 3 years ago but it has very little or no original equipment passenger car airspring business with major OEM's today. They do however supply the commercial vehicle market and the aftermarket. They did supply the very first airsprings on the classic Range Rover but Land Rover decided not use them for OE some 15 years ago. For that reason they DO NOT supply the original Disco 2 airsprings."
"The original part for the Discovery was supplied by ContiTech. I know because I was involved in the original business. I still am. We supply of course to the direct Land Rover aftermarket and dealers, however 4 years ago we decided to sell these parts directly into the aftermarket through recognised Land Rover aftermarket names. This was because of the very high price in the market and we wanted to discourage the spurious suppliers.
Dunlop being one. The ContiTech part in the market is the IDENTICAL part supplied to the OE business, using the same tools and process. The only difference is that Land Rover asked us to remove their part number from the bellow. Our number remains."

"There most certainly is not a tie up with Conti and Dunlop"

[assafde]

Issue was solved after replacing the air compressor.
Vehicle goes up after 15 sec while pressing the "off road mode"