Well your PSI is too low if that was operating pressure when filling the reservoir. You should see it peak between 240/250 psi when doing so. When filling the bags I forget the norm, but it is north of 150psi easily. I know for a fact 100 psi won't really even lift the truck at all. So I have to assume that the gallery pressure reading is at rest?

You seem to be confusing battery and alternator voltages. When running, you are reading the alternator voltage. When engineerings is off you are reading battery voltage. Standby battery voltage should be over 12 and is typically 12.3 to 12.6. Running alternator voltage should never get below 12.8 and should be 13.2 on the low side when all warmed up. When cold, you typically see at least 13.8 but often 14v. During really low temperatures, I have see as high as 14.5 but that is extreme winter.

So if you are not seeing pressure peaking near 250 and operating PSI when raising is low, you have a leak or a weak compressor.

 

Thanks Dakota. This is really helpful.

Electrics isn’t my strong point as you can probably tell.

Gallery pressure rises to around 97psi on start up before the infamous Ding after about 30-40 seconds.

As the compressor is only 2 years old, would you assume a leak somewhere has caused the compressor to overwork leading to premature failure?

 

What brand compressor is it? Hitachi or AMK? And is it a real one or aftermarket copy?

97 is way too low for operating. And yes they dont like to get abused. If I am doing work that requires lots of compressor cycles I tend to wait for long periods to cool it down. While it has a thermal cuts-off, that is way beyond what it should be. In fact a software update lowered the threshold - lowered the max operating temp.

With that said, it is still possible you have a leak. What I recommend is to get it to height, so the truck is like "okay, cool, no more lifting to do" and it is now at standard height. At this point, the compressor should still be running. This is when you want to take gallery pressure reading and see what it reaches before it stops - unless it faults out. Either way, need that number because when filling the reservoir the front/rear valve blocks are closed so you rule out leaks at those ends.

And if a Hitachi compressor, there can be an exhaust plunger that can fail causing a leak. Link to eBay as example only:
https://www.ebay.com/itm/163541858300

And also if a Hitachi or Hitachi copy, what usually fails its the cylinder. The walls basically melt and the piston starts to rip em up and it all goes bad. You can replace the piston and "head" with new.
https://www.ebay.com/itm/224167177667

 

AMK compressor was fitted 2 years ago by a LR specialist who is no longer around. I wasn’t overly happy with his work and never used him after that. If I recall compressor was around $650.

 

Well for that price, I would expect it to be a new AMK real one, not a knock-off or rebuilt. When it comes to rebuilding them, I am not sure if even possible. This is why I stick with the Hitachi. There is no advantage to the AMK but there are advantages to the Hitachi, especially when it comes to servicing.

Still, please to the reading I mentioned above to maybe help narrow things down. And of course get out the soapy spray water and look things over too. FYI, when the compressor stops its normal for gallery pressure to drop. That is by design and the compressor can not start up if its fighting 200psi. This is also why they often "fart" before or after operating, to dump gallery pressure. Gallery pressure is not reservoir pressure, there is no sensor that monitors reservoir pressure so the system, when filling the reservoir, infers the pressure based on gallery pressure.

 

OK I’ve got a few more leads for this weekend.

with the warning message kicking in so quickly it’s hard to get any readings.

however, interesting you mention the fart/purge. I’ve not had it do that in a long time!

 

So, Hazy IPA head and plenty of coffee this morning, I’ve been up playing around.

on start up I was getting messages saying in extended mode but no amber suspension warning.

I left run for around ten minutes. Gallery pressure was sitting around 96psi for first five minutes and again, suspension raising slowly.

compressor temperature climbed to 230F with gallery pressure climbing to 250psi before a purge, dropping it down to 14psi.

Raised the car and boom! All 4 corners raised without the delay on front raising. So is this an indication of reservoir not filling/leaking?

I’m going to do some leak testing today/tomorrow but did quickly spray the reservoir tank as there’s rust on the bottom corner of either end. No visible signs of bubbles.

 

Random extended modes can be cause by failing compressors. They move enough air to work, but the physical movement of the truck is not proper so it goes extended. I have seen that exact scenario twice where a new compressor solved it. Of course, it could be caused by other issues.

We need to get back to pressure readings... So it was running at 96 until when exactly... This is what I outlined above. Need to kinda know what is going on step by step. If it was running at 96 while raising, then reached height, then the compressor continued to fill the reservoir increasing in pressure quickly... Well if that is how it played out, then I would lean towards a leaking strut (likely in front) or a leaking valve block/line after the valve block, etc. Because if you are reaching 250 psi, that does not eliminate the compressor being at fault - but it reduces the odds a bit. Because typically a poor performing compressor not only pumps slow, but it also does not reach max PSI.

So if it played out above, then in theory you should be able to drop to access height after that cycle. Then when you select standard, it should raise pretty quick since the reservoir is now full. Make sense? Just dont go form access to off-road, no system no matter how perfect can go from access to off-road on the reservoir alone and you are back to relying on just the compressor for the final raise.

 

Still having issues but summary of Sunday events.



Sunday morning cold start up. No warning messages other than vehicle rising slowly. Drove for 15 minutes.



First 5 minutes gallery pressure hovered around 80psi, then slowly increased to 95psi. It slowly climbed over the next couple of minutes to 145psi then dropped back down to the 95psi, before climbing again to 145psi then dropping to 95psi. It then slowly rises to 245psi before switching off.



Temperature slowly rises, no crazy spikes here and voltage remains steady.



Graph attached. I missed recording the first couple of minutes but it’s a good reflection of what happened.

 

Then you must have a major or multiple leaks. On startup the truck should use already stored reservoir pressure from the last cycle. So it seems your reservoir or center valve block are leaking. And to get vehicle raising on a startup indicates the truck lowered pretty good overnight and now it has to run a while to lift and the leak causes it to go slowly.

edit: And you can’t rule out the chance the reservoir does have its own very small leak.