Disco 3 (LR3) Suspension fault. Compressor not running

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huntergaterer

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Hi.

This is my first post here.

So, I have a 2005 Disco 3 diesel. Got fitted a new compressor two years ago.

Yesterday I was driving on a very coarse gravel road with potholes and rocks. First i got the message: "special programs off" on the dash and the switch for selecting the height stopped working and the indicator light went off.

Then the yellow "suspension fault" message came on.

I got the car back home but the compressor had stopped working and the car sank down more than ever before.

I plugged in the icarsoft device and erased all the codes, hoping for a miracle. But, the compressor is still dead, the car is super low and the yellow suspension fault light is still there.

Plugged in the icarsoft device again and the C1A20 code, pressure increases to slow, is still there.
I checked all the fuses, they are good.

Thankful for any advice.
 
Welcome to the fun:).

If the compressor is only a few years old, I would suspect a leak somewhere as you have said it has dropped.

Time to get under it with the fairy liquid/Water mix and squirt it all.

I had the same code but also an over temp on compressor but the car stayed up, it was a knackered compressor.

Seems strange compressor wouldnt run after clearing codes, Is the relay ok?

File attached is for the L322 but they do seem to be the same.

J
 

Attachments

  • C1A20.pdf
    146 KB · Views: 373
Thanks marjon.

I will get under it and get dirty, but my knowledge is limited, how do i detect a leak if there is no air in the system
and the compressor does not start?
Also, how do i know if the relay is ok or not?
Sorry for my amateur questions, I can probably search the internet for answers..

I can add that i also punctured a tire during this ill-fated trip. The car got some beating, so I fear that I have wrecked something.

thanks
 
Yes you really need to at least try to get the compressor to run first. You could bridge the relay to see if it will run (for testing only) But as I have seen a well versed D3 member on I will call him, as I know he did a lot of work on his system @gstuart your help is required.

J
 
Update.

So the car has been sitting for more than two weeks.
Today I started it, and voila, the compressor runs again!
I get the message "filling to slow" or something like that, but it eventually filled it all up.
However, the compressor comes on and off.

So, I suspect a leak.

Is there a good write-up for detecting leaks in the suspension system?

Thanks.
 
A liberal application of soapy water on all the air lines is a good way to tell if any are leaking.
However don't assume the air accumulator is air tight, as they generally rust though before the plastic line seals give issues.
 
@huntergaterer Plus 1 ^^^^^

if u can’t find any leaks , put the disco into normal ride height , then measure from the centre of the wheels to the bottom of the wheel arch , then in the engine bay pull the fuse F26 , leave overnight and see if it drops, remeasure all the wheels and see if they match the first measurements u took

by doing this is can sometimes help identify where the leak is, particularly if just one corner drops etc

plus here’s some manuals for u which goes into more detail of how the suspension works etc

https://media.disco3.co.uk/gallery/albums/userpics/15405/Land Rover factory D3 air suspension description.pdf

when u open this link, just press download

https://onedrive.live.com/?authkey=!AMrvOm7c4l3jJkg&cid=4BC2D89C85C7C171&id=4BC2D89C85C7C171!2116&parId=4BC2D89C85C7C171!1330&o=OneUp

hope that also helps , plse let us know how u get on as many of us have rebuilt these suspension systems so plenty of us to help
 
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Hi all,
2006 D3 LHD with the same situation: compressor does not work
does anyone know which relay pins need to be bridged in order to test the compressor ?
thank you
Giacomo
 
Engine bay fusebox R7's contact pins(30 - 87 / larger perpendicular ones), don't expect it to inflate cos the valves are closed all you can expect is to hear it buzzing eventually... to diagnose it correctly see attachments
 

Attachments

  • D3 suspension diagnostics.pdf
    181.1 KB · Views: 147
  • D3 Suspension diagrams.pdf
    143.4 KB · Views: 102
Last edited:
Thank you sierrafery
ok they are pins 3 and 5 of the relay respectively, so if the compressor starts and I don't expect it to inflate the suspension, what else can I do ?
 
Hi,
I bridged the contact pins 30-87 and in fact the compressor started, so I thought the relay was faulty and I fitted a new genuine Land Rover LR126493 one, but the compressor stopped working
I tested the jumper again and in fact I have 12V at the connector and the compressor starts, but when I fit the relay I have 0 V at the connector ,where is the problem ?
however during the test I ran the compressor for about 2/3 minutes but the suspensions did not rise.....
I also read the many error codes: U0122 - U0421 - C1A72 - C1A73 - C1A74 - C1A75 - C1A27 - C1A03- C1A04 - U0416 - C1A20
 
giacomo.m said:
however during the test I ran the compressor for about 2/3 minutes but the suspensions did not rise.....
I also read the many error codes: U0122 - U0421 - C1A72 - C1A73 - C1A74 - C1A75 - C1A27 - C1A03- C1A04 - U0416 - C1A20
Click to expand...
Forcing the compressor with bridged relay would eventually kill it, i told you that the valves are closed so it can't inflate just pumping against itself, the relay doesnt close cos it's disabled by the management as a fault is present, bridging a relay is not the way to troubleshoot a D3... i attached you the doc with the suspension codes and possible causes but you have to understand how that system works and it seems you don't.
 
I know that bridging the relay is not the way to solve the suspension problems of a D3, I have read the suspension codes and the possible causes but then doesn't it seem strange to you that the 4 height sensors all broke together ?
now the car stands on bump stops, so it is also problematic to lift it to check the connectors in the wheel arches
 
Did you check live inputs from the sensors and they all read zero?... also if you clear the codes all of them are coming back or permannent?
 
sierrafery said:
Did you check live inputs from the sensors and they all read zero?... also if you clear the codes all of them are coming back or permannent?
Click to expand...
Yes,
we jacked up the car, first from the front-left wheel, then rear-right one. height sensors reacted issuing a much higher voltage but the compressor did not start.
I delete the error codes but they return immediately......
 
So in conclusion the sensors are not at fault... you must understand that you can't make it inflate the bags as long as those codes are permannent, once the problem is fixed and the codes are gone for good then it will work untill then you can't trick it and expect it to inflate by jacking it or bridging relays... those permannent U codes are to worry about as there is a complex communication issue or an ECU failure... somebody who knows exactly how this system works is needed, you can't DIY unless you learn the operation mode
 
Plus 1 , also have u checked the connections behind the front wheel arch liner behind the near side or ur drivers side

Also not a good idea jacking the vehicle up without disabling the suspension first , ie removing the fuse F26

In the picture the blue one is the feed to the compressor , plse check there first to see if u gave power but as mentioned need to clear the codes first, then check for power , otherwise they will come back straight away

Behind that front wheel arch liner ur also see some earths , best to clean them at the same time

those 3 x connectors were moved after 2007 to behind the front headlight , alas not sure if it’s the same on the LHD LR3 , so to save u time might be an idea to quickly check first , if not then behind the wheel arch liner

If u look on the wiring diagrams also shared by @sierrafery of the valve block and height sensor wires where u can match up the PIN numbers per connector shown below in the first picture , there are reports that these can also fail , with dirty pins or broken wires , if u pull them apart very easy to then test from end to end with a multimeter

Know it can be frustrating but just go through it step by step, personally also use a notebook as then u can write down the results as u progress

Plus of course using the live data of ur diagnostics , the pressure sensor has a 5 Vdc supply

So please clear the codes first, don’t do a rescan, check the Vdc to the compressor on both sides of the wheel arch connector and at the compressor , simply going back to source being the ECM behind the dashboard, along with ensuring all the fuses shown on the wiring are ok

Before I forget , plse also check ur steering wheel angle sensor is correct and set accordingly

Hope it also helps u

IMG_2003.png
IMG_2002.png
IMG_2001.png
 
Last edited:
gstuart many thanks to you too,
I will also do these checks hoping to reach a positive solution,
the photo of the front height sensor connectors is excellent, but do you know where the C0377/C0391 connector for the rear sensors is ?
 
As long as you have those permannent U codes you are checking sensor issues in vain, all the C codes are the result of those communication errors IMO...let's hope i'm wrong
 
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