I have a 2006 LR3 with a "Suspension Fault" warning. There is a bit of history here so I will try to be brief. I had an air leak at my front air valve block that caused my compressor to run almost continuously and I burned it up. I replaced the front air block valve and the compressor still ran but did not generate sufficient pressure and after a while, I'd either get a "compressor too hot" or "normal right height only" warning. I replaced the compressor (AMK), but did not change the relay. Upon startup, the compressor runs for split second and then I get the "suspension fault" warning and the compressor stops. I thought there was a problem with my new compressor so I jumpered the relay and the compressor started up. After a minute I shut it down and bled off a lot of pressure in the reservoir, so I proved it worked. I then noticed that my rear right tire was jacked up to 23 inches and I had no way of getting it back down because of the suspension fault warning. I cracked the airline on the shock and bled it down to the bottom. I then tightened it back up and jumpered the relay again. As I did this, I watched the rear right tire rise and then pulled the jumper after a normal right height was reached.

Other things I have done:
- pulled fuses and checked for sag overnight: no issue
- soapy water on all connection points/air blocks/air shocks: no issue
- check resistance off all fuses: no issue

My thoughts: When jumpering the relay, I would not expect any wheel heights to actually change. Because the rear right changes, this leads me to believe the reservoir air block is not functioning as it should. However, this does not explain why only the rear right is affected, you'd think both tires would rise if the reservoir air block was leaking by. So could this mean there is also a problem with the rear air block? Despite all of this, this still does not determine my original issue of the "Suspension Fault." Could the relay be bad as well?

I plan on replacing the reservoir and rear air blocks and also the relay. At this point, everything in the system will have been changed so hoping this fixes it unless someone has another suggestion. Could the ECU be involved in this somehow and causing issues? I suppose at the end of the day, I can take it to the dealer as I don't have an IID tool but figure swapping parts is an easy thing to try when compared to the ridiculous rates LR techs charge.

 

I'm sure others will chime in, but I believe you also need to perform a software update to the compressor when you go from Hitachi to AMK....that and of course the new relay. If you had an IIDTool you could do this s/w update and recalibrate your EAS (couldn't hurt). That may be worth the price of admission; I think a BT version is around $500 these days.

 

Thanks. I should have mentioned I had an AMK compressor previously and replaced it with an AMK.

 

You don't require a new relay when replacing the compressor, that was just a general maintenance procedure since a failed compressor can sorta "burn up" the relay. Also all the relays are interchangeable with others in the box if needed for trouble shooting.

The front/rear valve blocks control each side individually, so yes you can have a o-ring failure that could raise just one side. And you are right, if the compressor is jumped nothing should move and the reservoir will not fill. In fact the exhaust will blow out on the compressor which is a mechanical failsafe. No damage, just a blow off to dump the air pressure going nowhere.

What you need is a code.

 

Thanks. Interesting about the reservoir. I didn't realise that wasn't supposed to fill either when the relay is jumped, because it certainly is in my case.

I tried another relay, no luck. Suppose if I don't want to buy an iid tool, I should probably take it in and pay to have the code pulled and may an hour or two of troubleshooting so I don't waste my money on random parts I don't need.

 

The center valve block seals of the reservoir, it only fills after the vehicle is at proper height. So vehicle heights take priority. Basically in a healthy system the compressor will start and just a split second later the reservoir will open to assist in lifting. As the compressor drains the compressor essentially takes over until the vehicle height is reached. Then the center valve block will remain open until gallery pressure reaches almost 250psi, at which point the center valve block closes and the compressor shuts off while making a brief "fart" to vent gallery pressure a bit.

Codes really help a lot on this system. Not always the perfect answer, but often it can help narrow things down quickly. The warning coming up REALLY fast almost always points to a compressor issue though. If the compressor did not run at all, then its usually a calibration/heigh sensor issue. Something that is checked before the compressor would even run.

 

Interesting enough after reading this, I put my old compressor back in. No more suspension fault warning and its running, albeit with degraded performance like before. I may still have a problem with my reservoir air block still but there is definitely a problem with the new compressor.

 

My guess is the newer compressor is driving too much amperage, hence the quick shutdown. That could, in theory, even be caused by an internal short of the motor. So it could indeed mean a defective compressor. If not a genuine AMK I would not be surprised, if genuine then I am since they hold up fairly well.

 

Have you tried a new 60A fusible link in the engine compartment fuse box? It's bright yellow and the only 60A one in the box. I got one from AutoZone for $6, which reminds me I ordered 2 extra ones and they didn't call me to come get them yet.

 

Closing the loop on this thread. I ended up returning my aftermarket AMK compressor after much back and forth with the supplier. Picked up a genuine AMK compressor from an autowrecker and the problem was fixed. LR3 is back on the road! As others have said, be cautious of the aftermarket compressors which cost 1/4 of the price. The may look good but the seem to be garbage or at least hit or miss what you get.

Thanks all!