Suspension Faults

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Originally Posted by garrycol

Graeme - being a D4 that would have been an AMK i guess. Not familiar with them but if it can be changed without removing the compressor that would be great.

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Not initially an AMK. An AMK was fitted under warranty as the 3rd compressor just prior to the start of the general replacement program.

Ok car running in the drive and changing heights and no issues.

I put everything back in and tightened up - again running in the drive no issues.

Went for a drive and for 15 minutes all was OK - then gong "normal height only" - plugged in the Faultmate and it showed 2 suspension faults.

1. U0416 - Invalid data received from vehicle dynamics control module - Bus signal failure, signal is invalid - pending

2. C1A20 - pressure increase too slow when filling reservoir - Algorithm based failure signed plausibility failure - permanent

Then in the 30 degree heat the Faultmate overheated and caused HDC, transfer case, gearbox and over heating faults that all disappeared when the Faultmate was removed from the OBD2 port.

So given the car was OK yesterday - what is the consensus of the issue? If I do get a new compressor am I still going to get these faults, given I essentially have a new compressor at the moment. Is there anything I should have replaced when I rebuilt the compressor.

Advice appreciated

Garry

The pressure sensor for the reservoir has been known to give false readings. You could monitor the reservoir pressure, which should start to rise as soon as the vehicle is at the target height (normal/access/off-road) then continue rising with pressure slowing as it gets close to the cut-off pressure. If the pressure doesn't initially rise much even though the compressor is capable of raising the vehicle to off-road height at an earlier time then suspect the sensor. If the compressor stops to cool and you see the pressure dropping then the reservoir valve is not sealing.

Bear in mind though that the reservoir is held at a higher pressure than that required to get to off-road height.

It may be possible you have a leak in the system somewhere making the compressor work harder and not achieve full pressure. Take Graeme’s advice and follow his steps to gather more data on the issue

Quote:

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Originally Posted by Graeme

The pressure sensor for the reservoir has been known to give false readings. You could monitor the reservoir pressure, which should start to rise as soon as the vehicle is at the target height (normal/access/off-road) then continue rising with pressure slowing as it gets close to the cut-off pressure. If the pressure doesn't initially rise much even though the compressor is capable of raising the vehicle to off-road height at an earlier time then suspect the sensor. If the compressor stops to cool and you see the pressure dropping then the reservoir valve is not sealing.

Bear in mind though that the reservoir is held at a higher pressure than that required to get to off-road height.

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Thanks - I will remove the valve block and clean out again as I agree with your logic - I just loosened the hose from the block to the air tank and there is lots of pressure in the tank which has now drained away - now I agree the pressure sensor needs checking/cleaning but without a Gap type tool how do i do what you have suggested above - i only have a code reader.

Thanks for your help - much appreciated

Garry

Removed the valve block and cleaned it again though didn't need it.

Then same as yesterday - started up with no faults - I dropped from LLAMs -15 to access and then back up to normal onroad height - just gave the same slow rising message as to be expected with an empty tank.

Went for a drive moving up to LLAMS +30 and no issues and then back down to normal onroad height - 20km into the trip the fault came back - reset and 5km back, reset then 3km back, reset then 500m back and then basically the fauklt came back almost immediately on reset. It was the C1A20 fault.

So playing around with the valve does seem to fix the issue for a short period so you may be right Graeme. I guess you can buy Pressure Sensor by itself though I wonder if I should invest in a whole valve block as the little rubber seal at the bottom of the solenoid plunger looked well used.

I am gonna pull the air compressor back out and just double check that the cover on the desicant chamber did not cause an issue when I screwed it down as I could hear crunching inside, so maybe the supplier provided too many beads and coud be causeing a restricted airflow - I dont think so but I will check.

I did a leak test and all was OK around the valve block but where the pilot air pipe comes out of the dessicant chamber cover there was a leak from the orange connector but the blue air outlet was fine.

Garry

Sorry, its so long since I used my Faultmate MSV that I had forgotten that not all Faultmates can show live values.

I also can't recall if an IIDtool can read live values on vehicles other than the one its registered to. I know they can read faults codes on other vehicles but you need live values.

Thanks Graeme .

I took the compressor back out - it is surprising how quick you can do it when you are practised.

A few of the beads I had just put in had got cracked during the process of reinstallation but all seemed pretty normal - except for the colour of the beads. When I put them in the new beads were a brown colour, but when I took them back out after a day the top 2" of beads near the outlet were now green and the bottom 2" down near the piston were still brown. I put it all back but took teaspoons of beads out and the little bit of green dust that had formed when the beads were originally installed.

The pilot air pipe that comes out of the dessicant chamber cover is leaking from its orange connector - I cannot get the pipe out to reinstall it but very little air escapes but I will put a little sealant around to minimise it.

I bench tested the compressor, and with my finger over the outlet the airflow does not seem very strong. I can almost block it off but not quite - a little air still comes out so must be OK but I would have thought the pressure would have been higher - so maybe the rebuilt compressor is the issue.

Thanks for the contributions.

Garry

Sounds like enough pressure to raise the suspension but not enough to get the reservoir up to pressure.

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Originally Posted by Graeme

Sounds like enough pressure to raise the suspension but not enough to get the reservoir up to pressure.

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Yep - maybe time to bite the bullet and get a new compressor.

The obvious choice is the new AMK kit but they are about $1500 here and from the UK.

The cheaper ones, often sold as AMK type are knock offs ($600) RANGE ROVER SPORT AIR SUSPENSION COMPRESSOR KIT - COMPLETE - LR072537 -LR045251R | eBay - and they may be OK but I dont know.

On the Hitachi side they are all knock-offs - Dunlop ($850), Bearmach and Britpart (I think these are Dunlops but I dont know) - mixed reviews on this lot.

Then there are the Chinese knock offs on Ebay like this For Land Rover Discovery 3 Hitachi Type Air Suspension Compressor Pump LR023964 6941503307842 | eBay - again may be OK but who knows.

Garry