Hello,
I have 03 Disco SE7 and having find trouble with Real suspension went
all the way down and wont come up.
on the dash, SL light keeks on 5 seconds after start.
so, i took the compressor unit out, and proved it,
it works find when i open(disconnect) the tiny hose goes to the twin valve(1 for right 1 for left airbag. but with the hose connected, after the pressure build up, it will run for like 5 seconds and circiut braker pops out on the prove i have.

i checked all ohms on valve, and will read 14.1 on all 3.

and there is no power goes to compressor with 4 door closed and running.

checked relay and relay's switch point will not get power to make it contect the others poles which will goes to compressor unit.

according to wiring diagram, replay's switch point would be 1 for ground and 1 goes to SLECU.

is it SLECU problem?

 

had the same problem......took out the air bags, pump, went to coils.
no worries, no problems.

Ralph

 

I just fixed my SLS too...by swapping to coils.

However, it sounds like you answered your own question.
If the compressor works properly, and all 5 doors are shut with power on and no power/signal to the compressor to run, then either the signal isn't being sent from the SLABS ECU or there is a break in the circuit somewhere in between.

 

ok, Update for diagnostic.

1st try after inspect all funtions of compressor motor, valve block, hoses, and etc,
(after re connect battery) started car up, it rase up to normal hight.no warning light.

took it for drive and 1min after, warning light came back on and car starts sits down.
ended up came back to shop with bumpy rear suspension.

okey here is main story.
when the car running with all doors closed,
the voltage out put that i check, twin valve block has 14v on each side which would be normal(it will make the valve open so let the air flow from compressor to airbag),
and exhaust valve will get 3.8v which will not make the valve open(normal),
so far, she is cool with me.
but after inflate both airbags to normal hight, exhaust valve just open for couple second, and close(lost little bit of air), and i turn the key off and on exhaust valve opens again(lost another amount of air-lost about 1 inch hight already), everytime im turning the key off and on exhaust valve will get the air alltheway out on airbag.
I Only can think of SLABS ECU tells the exhaust valve "hey car is on too high, get it down"
plus compressor is not getting any power at any time now but when i prove it, it will run fine. it just wont get order from SLABS ECU.

so I made my own possibilities,

1 SLABS ECU-malfuction?
2 Hight Sensors- I heard they dont usally both go out at the same time.
3 SLABS ECU lost trac- domb computer might forgot how high the car supposed positioned at.

what do you guys think?


03 DII SE7 -120,000 miles

 

First of all, you guys aren't "fixing" the SLS by going to coil springs lol.

Really you need to plug in a code reader and get into the SLABS ECU. If the height sensors were malfunctioning or calibrated incorrectly, the ECU would disable and you'd have a solid SLS fault light on the dash. It wouldn't inflate at all.

As I stated in the other thread, the SLS system inflates opposing sides first, THEN deflates the required side - exhaust valve operation following compressor use is normal (even though admittedly it seems rather counter-intuitive).

"everytime im turning the key off and on exhaust valve will get the air alltheway out on airbag."

^This is the only statement that makes NO SENSE to me at all. I wasn't aware of any situation or code in the system which would ask for this to happen, even if the system is in fault mode.

Are you checking voltage at the exhaust valve and saying it's commanding it to dump the air till it's sitting on the bump-stops? Or are you saying that after you turn the car off, it LEAKS out. Big difference.

Honestly, it sounds like your compressor is dead. 3 things lead me to believe this.. first, the fuse blows (but only after some period of time, from what you stated. This points to seized motor, water damage, etc. This is normal). Second, it works fine when there's no pressure - this is a typical failure mode for a compressor motor; works okay if it isn't under load. Third, I know for a fact that SLS compressors are weak and fail often.. placing it top on my list.

NOTE: The system is more complicated than many people think. If you're checking voltages, all valves must be plugged in, since the SLABS ECU can determine the health of the system based on resistance from each valve. It knows when they aren't plugged in, even if it's not trying to use them - the system will disable and go into fault mode.


What's the status right now again? Now the compressor won't turn on at all (from SLABS) even though you can get it to turn on manually? Keep in mind that manually triggering the compressor may damage something, since both control valves are going to be closed.

I'm just confused because you say the car is dumping air at certain times, but also that the compressor isn't working now.

I'd do what I did and just replace the compressor with a Viair unit and external exhaust valve of similar resistance. Put a "tee" fitting on the hose that goes to existing compressor.. and attach one to new compressor, and the other to the exhaust valve. Put a one-way fitting in-line with compressor to prevent leaking (many have them built-in).

Use a code reader, it provides a LOT of information - even if the valve blocks are over their recommended cycle limit! If the compressor is outside of its' performance envelope, it should tell you as well (if it fails to inflate after a certain amount of time).

 

^This is the only statement that makes NO SENSE to me at all.
^I agree with you, but too bad, it dose that.

everytime when i turn key on all 3 valves are open for 2 second.
including exhaust valve.

and the voltage is important to check i think, because the valve's operating
voltage is more than 12v. yes, evrything was hooked up right before i do anything,
(i dont use multimeter, the prove tells me what the voltage is.)


when i give power to it i can see it working with my eyes and already figured
how air trevels inside compressor and valve block.

and like i said with the car running, ECU will let twin valve open and exhaust valve
closed, but compressor isnt get order from ecu.

this is the "ONLY" point if i manually operate the compressor, it will inflate fine.

than,!

when i turn the car off, its fine, but key on, it will lose air through exhaust valve.
while air is goin in and out of exhaust valve, it clearly getting an order from ECU.
according to voltage comes out of ECU and the clicking sound i heard.
i mean it is not defecteve valve.

and, code reader...

should i go to dealer and let them read code for me....?
I trust mechnics there but i would not trust service advisers...

 

Ehh you might be looking into it too far about the 2 second thing - sometimes mine dumps air when I open a door (and key is off) or when I get out of the car (key off) especially if there's an outside temperature increase (air expands). That could be normal.. the valves I mean. Those sound fine, I'd focus on the compressor.

Okay thanks for the part about it opening the left and right control valve (with exhaust closed) obviously means the SLABS ECU is trying to inflate the suspension.

Are you 100% sure that the fuses, relays, and the larger fusible link are ALL okay? Sounds stupid I know (sorry) but that's my very strong gut feeling right now.. from what you're saying it sounds like your SLS system is working perfectly (err, trying to anyways) I'm really convinced that one of those is blown (again, probably as a result of a dying compressor). Either way, the problem is isolated somewhere after the SLABS unit and before (or including) compressor.

Good luck!

 

Just checked fuses and relays, those were fine. switched relays around, no change.

ye, it is true that the car drops down about 2cm after turn off and will raise up
after turn on and my disco did that when she was "NORMAL"

heres what i forgot to say

when the car inflate to normal hight,(i can inflate it by manually) -> turn off-> wait for littlebit->exhaust valve will let air out for second and closed->right now im fine.
than, ->wait for another hour(no metter how long tho,)-> key on->
"3 VALVE IS OPEN!" and close after 2second->lose air again->start it up->
Left and Right Valve open->exhaust valve closed->compressor is not getting power->
end up, inflate by manually(let the relay contect by finger)...doing this circulation for 5 times now.

so what you are saying is

->compressor could be fault on ECU but still could work manually?

oh here is another thing

when i disconnect hose from compressor air outlet and get it running manually, and block the outlet hole with my finger, the braker pops out of my prove. it is less than
30A but the compressor looks weak to me too.

when is weak tho, it dose inflate the car. that is main thing i dont doubt that thing.

so im pulling my hair out ALOT...

Just thinking this too if i want to do 3 in lift springs( i might give up SLS),
do i just need to chage springs and thats it? or should i have to replace some componants?

 

Yeah, so under load the compressor blows a fuse? I wouldn't stress about that - the Viair compressor I replaced my OEM one with was only like $100! I was just going to leave the OEM one in there (so I could keep using the internal exhaust valve) but I stripped the plastic threads, so I took it out completely and used an aftermarket solenoid for the exhaust valve too.

The SLABS ECU will store compressor power supply fault codes that you can read with TestBook (needs to be the full LR-approved system, not just a basic OBDII scanner)

So you checked the fusible link 9 (the big fat fuses that look different?) This provides power to the relay in addition to the other two regular fuses for the SLS system.