Thread: Wabco Air Compressor for rear airbags running even with engine off

I reckon your SLS relay (R216) in the engine compartment fuse box needs replacing. Sounds like the contacts are stuck in the energised position.
Pull the relay and see what happens.

After you shut off the car and remove the key the Disco will continue to self-level for another 30 minutes. The is a feature to maintain the right level as passengers and luggage are removed (or added I presume) from the car. eg if you remove a heavy item from the back you should hear the sound of air being released.

But the compressor should only run of course to level either side, then switch off. So as long as you don't have a leak anywhere in the system (usually the airbagsm which you say are almost new) I would look at the electrics. RAVE provides a good description of how the system works as well a the wiring diagram if Biggin's tip doesnt work.

Good luck !

Hi Simon,
If, as you say, the compressor continues to operate (if needed) after the ignition is switched off, I have never noticed this.
I have heard the air let go as you dismount, but never the compressor.
BTW, I'm not saying your wrong, just that I haven't noticed it.
Being as deaf as a fence post doesn't help I suppose.
I'll be listening closely in future.
Cheers,
biggin.

Hi again Biggin

Woops - you're right !

I checked RAVE again p64-17 to 64-20:

"Opening any of the doors will power up the ECU, irrespective of ignition switch position. The door open signal is
sensed by the door switch completing an earth path which is sensed by the ECU. The ECU cannot differentiate
between any of the doors. The door open signal powers the ECU for up to 30 minutes to allow the vehicle to re-level
when a load is removed or passengers leave the vehicle.
The SLS system is active when the ignition switch is in position II, when one or more doors are open and for up to
thirty minutes after all doors have been closed. If the rear axle is articulated by more than 100 mm (3.93 in), the ECU
will not activate the SLS system.
The air supply unit compressor will only operate to raise the rear of the vehicle when the engine is running, with the
exception of the remote handset operation which does not require the engine running."

Most usually as stated a stuck relay. I would attend to it ASAP as eventually the compressor PLASTIC air fittings will melt...


JC

hey guys,

Thanks heaps for that advice! I only just got back from work but I will check that relay pronto!

yep that seems to be it at this stage. Not only had the suspension not sagged overnight but when i opened the door it sunk a few inches straight away before leveling out so the poor bags must have been fit-to-burst!

yanked the relay and gave it a couple of wacks against the wall and then tested, started engine and tested again and it seem good. I will replace the relay anyway but it is good to know that may be all there is to it!!

Very much appreciated, thanks again.

oh and the relay was an R6L5 not an R216 but that may not mean anything special.

oh sweet! I thought i would give her a looking over, and i see her transfer case number starts with a 41D. YAY

looks like i have a home-made linkage to make.

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