2011 XJL SC. Working on tracking down an issue with the air suspension not working. I have a feeling that it is likely the control module, but want to rule the simple things out. The big 60a fuse was blown and though I replaced it, there has to be a reason it blew. I do have a parts XJL and I know it's air suspension works, but I want to spare my spare parts as long as I can.

I have gone through all of the fuses and all are good now. However, I know from the electrical diagram that there is a relay in the luggage compartment fuse box but I am not sure which one it is. I know Jag didn't want us commoners touching the relays, but they have abandoned us mostly and I am a relatively skilled DIY and the car is 14 years old, so I'll take the risk! I have looked all over and can't find which relay is for what. I am not expecting it to be a relay, but I have been bit hard by assuming in the past. Thanks!

Mike

It may just be the compressor motor itself. If there was a leak in the suspension (not common on these but it is an old car) and the compressor was running all the time to keep up, the motor could just be worn and start drawing a ton of current as the brushes or commutator bars wear down. I had that happen to a blower motor once. The grounds and feed wires were fine, but the circuit kept blowing fuses. Replaced the motor itself and solved the issue.

Perhaps, and I certainly haven't ruled that out as it is reasonable. That being said, I am getting messages related to being unable to communicate with the air suspension system, which gives me pause that the compressor is the actual issue. I am not in a hurry with this and do have the time to go through diagnosis.

I just realized the wiring diagram calls out R10 which I believe is the relay number. However, I'm not fully sure that helps much without a diagram showing me where R10 is actually located.

Hi farm-jag,

Relay 10 is located in the rear junction box, but it is possible that it is built inside the box and is non-replaceable. I do not know on the X351 and the Electrical Guide doesn't seem to tell us. R10 powers the air compressor, so you can easily test the relay by checking for B+ voltage on the Green/Orange wire at the compressor, either with the ignition ON or engine running.

Failure of the Air Suspension Control Module (ASM) is rare. By far, the most common problems with the air suspension are air leaks, a worn piston ring seal in the compressor, a failed compressor motor (sometimes due to water ingress), or a stuck exhaust solenoid valve (which is mounted on the compressor).

What are the symptoms?

Can your scan tool read the Chassis (C-prefix) and Network (U-prefix) diagnostic trouble codes? If so, what codes are stored?

Cheers,

Don

Hey @Don B Thanks for the response! I was aware that the relay could be a built-in kind as you mentioned but absent being able to rule that out, there is no way of truly knowing! In any event, there are not that many relays back there, so I tested every one and they all checked out. I figured as much. I can't remember how many times I have ever actually encountered a bad relay. Maybe 1 or 2 in my whole life! In fact, I have a Massey Harris MH50 tractor from 1955 and I was chasing a no start problem with it (spoiler, it was a corroded positive battery cable hidden under the clamp). Part of the troubleshooting was testing the ORIGINAL starter solenoid, so basically a relay, and it still works perfectly!

I digress. Symptoms I have are that the suspension doesn't rise. Additionally, on my other XJL that I have, I can invoke showroom mode to lift it even without starting the car. I have an Xtool D7 Scantool which works really well for Jags, but I do also have a copy of SDD, which I haven't tried. Figured, though, that if it worked on the other, it should work on this one. It goes through the motions, but I don't hear anything happening. I do remember seeing either a message on the cluster or in my scantool (or SDD) that referenced being unable to communicate with the air suspension. However, that has been awhile ago. I wanted to check all they physicals first, which I have done. Now I am charging my somewhat dead battery before doing any further testing, though I have a constant adjustable power supply that I use for programming that I can use if the battery is not charged by time I get back from my errands. Thanks for the tip on checking the relay at the pump itself. Honestly was thinking too far forward to do that simple test.

I will pull codes again and report back. Side note, I actually bought this one from an insurance auction (actually bought all of my Jags from there). It isn't salvage title either and I got it for a great price. The thing with this one though is that there is some heat/fire damage to the left side rear (bumper cover, light, pillar cover), BUT I am nearly positive there was no fire directly on the car itself. There is nothing burned, ashed, etc. Looks like it may have been close to a fire or heat source and melted plastic from indirect heat. I have checked underneath and all wiring on that side and nothing is even remotely melted so I don't think this issue is related, though it could be As mentioned, the 60a fuse was blown. Though I replaced it, still no go. There was a reason it blew and I bet when I figure it out, that will be also the reason I am having problems.

Thanks again!

Mike

Just to tie this up. I was never able to actually find/pinpoint which relay exactly was responsible here. However, there aren't that many and so I just tested all of the with my Powerprobe and multimeter and they all checked out. I think you are correct in that it may be the compressor. I finally got SDD hooked all up and ran the compressor raising routine. SDD said it was lifting the car, but it absolutely didn't. No noise at all fro the compressor either. At the time, I failed to check the compressor power wires to see if was getting voltage during the routine. If so, then I'd say def. the compressor. If not, at that point, I'd think maybe the air suspension module back there. I really want to hone my diagnostic skills with this one and don't want to simply parts canon it, even if logically it makes sense and even though I have a fully stocked parts car ready to have parts swapped out!

Hi Mike,

Curious if you ever got to the bottom of this. I’m seeing almost the same thing on my 2011 XJL:

• 60A air-suspension fuse was blown → replaced
  
• Repaired the melted 2-pin power connector at the compressor (using the updated loom)
  
• Swapped in a known-good AMK compressor
  
• SDD can run the air-suspension routines, but the car doesn’t rise and the compressor never runs
  
• No current suspension DTCs after clears, just “no lift / no noise” from the compressor
  

From your posts (and Don B’s reply) I know R10 in the rear junction box feeds the GN/OG wire to the compressor, and that the relay might be internal to the box. Before I go chasing the junction box / ASM side, I’m wondering what ultimately fixed yours – was it the compressor itself, wiring to the GN/OG feed, or something in the rear junction box/module?

Thanks for any insight – your thread is the closest match I’ve found so far.

Yep, I *thoroughly* tested all electrical related to the compressor and found nothing out of sorts. Tested the couple of relays as well and they were all good. Wanted to be sure it was absolutely nothing else before I swapped in the donor compressor that I knew worked. Swapped in the compressor from my parts car and it worked immediately! Where did you source your replacement compressor from? It is possible to quickly bench test the compressor outside of the car completely to verify that it is indeed good. Now if it is OE brand new (which I'd be curious how you obtained that!), then I guess you can rule the compressor out, but if it is anything else (used OE, aftermarket, etc.) then I wouldn't personally assume it was for sure good until I got it working on it's own. Good luck!

Thanks for the follow-up, Mike!

Quick follow-up from my side since I just went through something very similar on a 2011 XJL.

In my case, the chain was:

• Classic melted 2-pin compressor connector → fixed with the updated loom (C2D49620 harness).
  
• Swapped in a later AMK compressor from a newer X351 (same connector style).
  
• SDD would run the suspension routines, but there was no lift and no compressor noise.
  

I assumed wiring/module at that point, because the big 60A fuse looked fine and I hadn’t actually messed with it yet. When I finally dropped a different 60A into that slot in the trunk fuse box, the system woke up immediately. I heard the compressor kicked on and the rear lifted.

So for me the missing piece was:

• The original 60A fuse was bad even though it didn’t look obviously blown. It's fuse #22 in the trunk fuse box.
• As soon as I swapped in another 60A, the new compressor and repaired connector worked exactly as they should.
  

If someone finds this later with a 2010–2015 Jaguar XJ X351 / XJL rear air suspension not working, no compressor noise, melted compressor connector, or C1A27-14 / compressor circuit style issues:

• Inspect and repair the 2-pin compressor plug and short harness first (burnt black wire is common).
  
• Don’t trust a visual on the 60A fuse in the trunk fuse box. Just replace it.
  
• If SDD says the compressor is running but the car doesn’t move, check for 12 V on the GN/OG wire at the compressor plug during an active test:
  • 12–14 V present, good ground, but no noise → compressor/ground issue.
    
  • 0 V → fuse/relay/wiring/module side.
    

In my case, once the loom and compressor were sorted, the bad 60A fuse was the only thing keeping the system dead.

Thanks again for documenting your process. Your thread was the closest match and helped me narrow where to look.

Good diagnostic work and thanks for sharing your solution.