So...time to discuss compressors again.

I've started getting a slow raise error and noticed my compressor is running to long at start-up or when raising the truck. It is the newer AMK unit; about 2 years old. It still does the job, but in the spirit of sorting things before they fail I need to start thinking about what's really going on.

If this were an original Hitatchi, I'd start with doing the dryer silica, but I've never heard anybody talk about the dryers on the AMK. I don't actually know if anything significant changed in the dryers or not, but it seems if it's an issue with one it could be an issue with the other.

I don't loose much height when parked. Over night it doesn't drop noticeably, but if I leave it for a week it drops some. Not to the bumps, but it does slowly leak down. I don't really think this is related to this issue though.

I almost wonder if the air inlet could be restricted in some way causing the compressor to over-work. At one point last year I had this problem when I melted the plastic intake line where it passes behind the exhaust heat shields, but in that case it simply shut everything down with the Red Rover of Death on the dash. No error lights this time, just the occasional 'vehicle rising slowly' warning.

For some reason I my mind wants to look at the relief valve block at the compressor, though I can't say there's any real logic to that. I haven't studied the system enough to know if that would cause this issue or not.

Thoughts on this?

I won't be jumping into the job right away as I need to fix the rear CV joint I turned to shrapnel last Saturday first, but it's on the future agenda.

 

What codes are you getting? Does it raise too slowly going from Access all the way to Off-road quickly (only) or even when going from one level to the next one up?

How did you melt the lines? Were you doing something that put them in harm's way?

 

Just recently, there was a write up how to dry a silica beads on AMK on Disco.Co.UK forum .Yes, they getting the same symptoms now as they age as Hitachi with clogged up dryers .Cheers

 

I haven't pulled any codes on it yet. I've only gotten the 'raising slowly' warning twice when going from standard to off-road, but I've noticed the compressor is running longer than it used to. Just last weekend I had an interesting thing where the compressor would cycle on for a couple seconds then off then on...did that about 4 or 5 times. Didn't give me any warnings on the dash and I was driving so I didn't mess with it and forgot about it until now.

I melted the intake piping when I was experimenting with shorty exhaust. I had cut the exhaust off after the center muffler and put turn-downs on it, but the heat ended up being too much and it softened the piping where it passes along the center tunnel behind the heat shield. Once the plastic was soft the compressor pulled a vacuum that collapsed the piping in on itself and basically plugged it up.

Come to think of it, I'm not sure the compressor should have had that much vacuum. Maybe I should look at the air intake filter. I know it's somewhere in the cavity behind the driver's taillight but haven't dug into it to find it. I suppose if I just disconnect the intake line that should give an idea as to any restrictions.

 

I don't think it's abnormal for the compressor to cycle on and off a few times in short increments like that; especially if it was within 5 minutes of the first operation of the vehicle.

How many miles on the AMK? I'm surprised it's getting tired already. I'd also look at live values as this is happening. There could be a leak somewhere, making it hard for the compressor to make the final pressure in the gallery.

 

Like I said, I haven't actually done anything with it yet. I'm just gathering my thoughts prior to going after it. I'm sure I'll see the gallery pressure get to the correct number when viewing the live data, it will just take a while.

I'm going to say about 25K on the compressor; a little over 2 years old. I live in a pretty low humidity area here in NorCal, so you wouldn't normally worry much about the silica getting saturated but then again I've done at least a dozen water crossings as well so even though the intake is high and inside the compressor has certainly been dunked plenty of times.

I have replaced the front valve block not too long ago, but AFAIK the other two are original. They're probably due for replacement just as PM work, so I may go ahead and swap them when I get into it.

I'd be shocked if the compressor was actually failing, as in poor compression or internal damage. I'm sure the issue will be one of the down-stream components.

 

Probably...and I'm not sure about the valve blocks. I've been considering changing mine as preventative (original, 121k miles) but they work flawlessly now, so I may just leave them alone.

 

Finally getting around to working on the LR3. I'm still waiting on the rear axles so it's been back-burnered while I play with the RRCs.

First thing I pulled the codes.

VIN SALAG25407A419986
Model L319 - LR3 2007
Vehicle scanned on Apr 17, 2016 12:51:04 PM
IIDControl 2.6.1 Android - IIDTool BT V3.0 B2134
Instrument Pack
• U0132-87 (2E) Lost communication with ride level control module - Bus signal/message failure - missing a message
Parking Aid
• B1B48-01 (6C) Rear left outer sensor - General failure information - general electrical failure
• B1B44-01 (6C) Rear right outer sensor - General failure information - general electrical failure
• B1B50-01 (6C) Rear left inner sensor - General failure information - general electrical failure
• B1B46-01 (6C) Rear right inner sensor - General failure information - general electrical failure
Suspension
• C1A24-67 (6C) No temperature increase when compressor requested - Algorithm based failure - signal is incorrect after the event
( at 127968 mi )
Terrain Response
• C1A01-96 (2F) LED circuit - Component failure - internal failure
( at 127968 mi )
Transfer Case
• U0126-87 (28) Lost communication with steering angle sensor module - Bus signal/message failure - missing a message
( at 127968 mi )
• P2787-00 (28) Clutch temperature too high
( at 128651 mi )
Tyre Pressure
• C1A56-31 (E8) Front left wheel module - Frequency modulation/pulse width modulation failure - no signal
( at 127973 mi )
• C1A58-31 (E8) Front right wheel module - Frequency modulation/pulse width modulation failure - no signal
( at 127973 mi )
• C1A60-31 (E8) Rear left wheel module - Frequency modulation/pulse width modulation failure - no signal
( at 127973 mi )
• C1A62-31 (E8) Rear right wheel module - Frequency modulation/pulse width modulation failure - no signal
( at 127973 mi )

The highlighted items of interest, the rest I know about. For example, I'm not running TPS or parking sensors so those are expected; I also know the LED on the console for the terrain response is in/op.

The clutch over-heat is likely from driving out with the busted CV. That taxed the center diff.

I'm not sure about the 2 lost communications errors, ride level and steering angle.

The most interesting one is the 'no temp increase when requested' on the compressor. I'm not sure what to make of that at all.


I then let the truck idle and the compressor run until it stopped with the reservoir full and timed it going from access to off-road height. It took just under 1 minute to reach full height, but the compressor ran for about 3:10 to fully recharge the reservoir. That seemed long, but I don't have another truck to compare it too.

Motor temp got to 52*, while compressor temp was reading 201*. Ambient was about 75*

I'm going to drop my slider and clean everything up. I know I've got mud packed up in there because the compressor is rattling against the slider. Seems I have to do this a few times a year but so it goes, no big deal. I have tried drilling a 1/2" hole grid in the slider under the compressor to try to drain away some of the mud but it still builds up there.

While I'm there I'll likely go ahead and replace the valve block since I believe it's original (125K) and I have one on hand. I don't really think this will make any difference but it's good PM.

I guess the question is how long should an AMK compressor run to bring a truck from access to off-road? Is 3+ minutes too long? And what temps should I expect to see?

I may go ahead and run it again just to see if there is any noticeable change in speed when the unit is hotter. But for now I'll go ahead and do my work before testing...no point in making things any hotter before working on it.

 

After replacing the reservoir and rear valves I did the test again with pretty much the same results. Still about a minute to go from access to off-road assuming the reservoir is full at the start and 3 to 3:15 to compressor shut-off at an indicated 2000-ish psi (obliviously not a real number but that's what it's reporting)

I did it back to back and got the same thing, so the compressor is at least consistent. I got up to about 225* by the end of the second run.

I didn't bother pulling the compressor out to check the silica, but maybe I'll try that next week when I get back home if I have some extra time. Again, this compressor is only about 2 years old.

It seems to be more or less normal; I'm not sure what was causing the issues I saw before. The only thing that feels off based on these tests was the 3 min+ run time to refill the reservoir; that seems a little long but again I don't have a baseline to compare to.

 

I don't know that my AMK compressor takes quite that long to fill the reservoir but I do think that it takes a few minutes to stop running. Are you currently getting faults?

I thought about replacing my valve blocks but decided on a "if it ain't broke" approach for those components, especially since their failure is not catastrophic.