Unexplained SLS issue

**assafde** · 21st February 2012, 12:48 AM

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** · 21st February 2012, 06:17 AM

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** · 21st February 2012, 06:55 AM

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** · 21st February 2012, 07:58 AM

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** · 21st February 2012, 08:20 AM

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-...g-failure.html.

http://www.aulro.com/afvb/discovery-...d-morning.html

**stevo** · 21st February 2012, 08:53 AM

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** · 21st February 2012, 05:46 PM

My last set from pommyland were Trelleborgs(),, 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** · 22nd February 2012, 04:07 PM

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** · 23rd June 2012, 06:57 AM

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

**OffTrack** · 23rd June 2012, 07:12 AM

Originally Posted by strangy

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

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