And maybe not yet. I pulled the air spring and gave it a low pressure, basic test and it holds air. I put in a replacement fitting, and used AlfaOBD to put a little air in it, and it might be holding. However, I cannot get the compressor to kick in, either via AlfaOBD or via normal means. Alfa says the pressure is too low when running a few of the suspension diagnostics. So now I'm debugging the compressor

Yesterday, that corner was down hard, and the suspension wouldn't pump up all the way upon startup. It displayed a couple of "service air suspension immediately" messages, and I shut the system down at that point. Air escaped loudly from that corner as it settled to rest on the bump stop.

I'm searching for the fuse and relay locations to try to get the compressor running. Anyone who has been down this road before, please let me know. Even the numbers would be useful.

 

Going further: fuses J1, M2 and M15 test ok using a DMM.

Fuse descriptions: ᐅ Jeep Grand Cherokee (2012 - 2013) Fuse Box Diagram 🔧

The locations are embossed in the bottom of the cover. Hard to see but it is what it is.

Jeep Grand Cherokee (2011-2013) Fuse Diagram • FuseCheck.com

Fuse box diagram (fuse layout), location, and assignment of fuses and relays Jeep Grand Cherokee (WK2) (2010, 2011, 2012, 2013).

fusecheck.com

The above has a placement diagram and shows the relays (none of which are shown to pertain to the compressor).

Current state of the system: no compressed air in the reservoir, compressor doesn't kick in when expected. Rear left is very low (there is probably a little air in the spring), other three corners are at normal ride height.

I need to know how the QL air compressor is directly driven and if there is a relay and/or fuse in the circuit.

Update: Ran a few of the active diagnostic routines; some of them returned "airmass too low", none of them ran the compressor. However - I was able to get the compressor to run (and it sounds normal, woohoo) with the following:

1) cleared the codes; some of the diag routines set C2212 so you'll need to unset it if it appears. One of the original codes indicated the compressor was over temp. That was likely set yesterday.

2) using AlfaOBD, set the drive level to Park. The compressor ran, pulling air from the other three springs into the reservoir

3) set the drive level to Aero. The compressor ran, filling the 4 springs. I'm not sure if it pulled in outside air however. I don't know how to 'force' that to happen - eg fill the reservoir to full capacity...

Now, I have a level car. I still have a small leak at the left rear, able to be heard when placing my head close to the outside of the wheel. And - the two ride level buttons are flashing in an unusual manner: the High button's 3 leds are all flashing, and one of the Low button's leds (edit: the lowest one, so from back to front: flash off off flash flash flash) is flashing; all 4 at the same time, about once per second.

Still would love to find out if the compressor has a relay and/or fuse, outside of the TPIM's 3 fuses. And - how does the system determine it needs to pull in outside air? If there's a detailed tech writeup somewhere, I would be glad to geek out!

 

There is a relay and a fuse. The relay is a slow blow type overcurrent circuit breaker. It is designed to allow for the compressor start inrush current while breaking the circuit for longer term over current. You replace it with standard relay it will immediately blow the fuse... which is rated much higher than the breaker/relay. I think its in the smaller aux power distribution center, along with the DRL relays and something else..

The details and diagrams have been posted before.

I think I read here somewhere about a compressor lockout when deflated. The compressor is a low duty cycle type more akin to a tire inflator. It is not designed to fill from a deflated state. Its job is to move nitrogen around.

Otherwise I think your jeep is just upset you don't love it or care for it enough to fill it with nitrogen. It is moody.

 

 

Well I do keep promising it some class 5 nitro! But I think it doesn't believe me.

I'll keep searching for the details. Right now I know the compressor, relay and fuse are ok. I'm tackling this like it would be a field repair, so if it happens again and I'm stuck somewhere, I know how to react.

The way it sits now is pretty decent and I think that corner is holding at least a little pressure. I decided to lay off of it for the rest of the day, so I don't strain the 11 year old compressor, haha!

 

We crossposted. Thank you! I was trying to find online wiring diagrams but came up empty. That helps immensely. Now I need to figure out how to get the system charged with air, and what those flashing lights on the up/down console buttons mean

 

Update on the relay, based upon the wiring diagram that @ColdCase provided. It looks like the air suspension compressor relay is the one on the far left, in the small, black relay-only box mounted behind/above the main TPIM/fusebox. There are slots for 5 relays, some will be populated depending upon options (for example, this one doesn't have headlight washers & but the other options are present, and there are 4 out of the 5 relay slots that are populated).

I'll upload a few photos. The relay has 5 lugs and is larger than the three other ones.

Other than ordering an air spring or 2, I'm still looking to find out about the flashing lights (I'm sure it's some kind of error condition) and how to get the system to pull in fresh air as expediently as possible. Again I'm running AlfaOBD to make all of this possible

 

Since finding the WK2 Maintenance and Repair Thread Index that ColdCase put together, I've learned a lot from the following: Air Suspension Pressure

A couple of important points: I really should have class 5 nitrogen in there for a variety of reasons, and it probably isn't possible for the air compressor to fill the system from external air from a low pressure situation. At least I'm out in Denver where the humidity is low.

Thanks to @ColdCase for all the help, once again!

 

I'm back to shopping for a set of air springs. Any suggestions?

I can either go cheap to get by, get something solid and reasonably priced , or get something high end (like Mopar, I'm guessing).

edit: are Air Spring | Arnott | Rear Left or Right | Jeep at $252 a pretty decent way to go? The other site said Arnott stuff is good quality (better design & material). Amazon has 'em for $206 delivered as well.

 

If you search this forum for Arnott, you will find several favorable reviews. Said to be pricier but good quality.

 

Thanks and I appreciate the advice. I'm looking at doing the Arnott front strut assemblies. It needs struts all the way around in terms of ride. Buy once, cry once I may get a single, cheaper rear air spring for an immediate fix, then swap that out & store it when I get better ones like the Arnotts.

Arnott AS3323/4 front strut assemblies, a pair of the above Arnott rear air springs, and a pair of Bilstein 4600 rear struts seems to be a great way to go.

I'm thinking of getting one of these less expensive, rebuilt units from RMT:

Rear Left or Right Quadra Lift Suspension New Air Spring for Jeep Grand Cherokee 2011-2015

Find amazing deals on Jeep Grand Cherokee 2011-2015 New Rear Air Spring. Order today and receive Fast Delivery and Discounted Prices!

rebuildmastertech.com

It's $90 with free ground shipping. (edit: unsure of the fitting, though)

 

The RMT spring went in over the weekend without issues.

I had to run an air mass calc using AlfaOBD a couple of times. That part seemed to work better with the engine running, but don't know for certain. Drove it a few miles and once the reservoir filled, all seems okay. There wasn't an elbow fitting included; I reused one taken off when doing previous maintenance.

The toughest part about it was raising the Jeep with a cheap-ish floor jack.