from what i can gather from that pressure switch is that it monitors what pressure u have in the system
the hiss will happen when the compressor switches off, once that happens u will hear the quick burst of air, like when u take a tyre gauge off a tyre, a quick release
if it isn't raising , what is the compressor pressure according to ur diagnostic machine
could the compressor becoming tired , not having enough guts in it to raise the body
there's a pressure chart somewhere
see if i can find it for u
don't buy another pressure sensor , i've got a second hand one , somwinder about comparing them maybe
don't know if i can via a multimeter maybe in ohms , etc
maybe someone more experienced would be able to verify if the pressure sensor can be tested
when the compressor is working , can u hear any air escaping , have u tried soapy water on the joints
i've still got to replace my reservoir valve ad air tank , which i already have , just got to fit them , also bought an inlet exhaust silencer
by the way have u cleaned out the air inlet filter that sits in the boots cubby hole, as u look at the landy is on the passenger side , the one by the back lights
it's a black round container that has the filters inside
wonder if any white silica has chocked up ur resevour valve
suppose the first port of call is to find out what pressure ur compressor is outputting
20th Feb 2017 1:39 pm
gstuart
Member Since: 21 Oct 2016
Location: kent
Posts: 13635
[quote="dabware"]Hey Gary
So my current thinking is that there could be an issue somewhere down the line, the compressor seems to work ok and if it dumping excess air via the hiss then I am confused as to why this is if the suspension is not raising. There looks to be a pressure sensor on the central junction so not sure what that is monitoring although it does look to be before the air tank so I wonder if there could be a problem in this area and its not filling the tank.
I have attached a diagram that I recovered from one of the online Landrover manuals that seems to explain how things work quite well
here u go
the pressure gauge chart
see what urs it,
hope that helps abit
Click image to enlarge
20th Feb 2017 1:43 pm
gstuart
Member Since: 21 Oct 2016
Location: kent
Posts: 13635
pressure sensor description
Reservoir Pressure
The reservoir valve block also contains a pressure sensor which can be used to measure the system air pressure in the air springs and the reservoir.
The pressure sensor is connected via a harness connector to the air suspension control module.
The control module provides a 5v reference voltage to the pressure sensor and monitors the return signal voltage from the sensor.
Using this sensor, the control module controls the air supply unit operation and therefore limits the nominal system operating pressure to 16.8 bar (244 lb in2).
Maximum pressure is a nominal 23 bar (333 lb in2), however the reservoir is tested to a maximum of 35 bar (507 lb in2).
20th Feb 2017 1:46 pm
dabware
Member Since: 02 May 2014
Location: Ashford, Kent
Posts: 9
So i just sat in the car and put the IID on to see what was going on
The car is currently in access height so I started the engine and watched the pressure. This was at around 18psi then I selected normal height and the pressure increased to about 54psi in about 5-10 seconds and I got a ding then the compressor shuts off so the pressure then drops to 18psi in about the same amount of time.
I had a nose around the IID tool and managed to dump all of the air from the system and after running it for a couple of times it looks like no air is getting back into the system at all. I still have the air supply fault on the IID each time.
I am not stuck yet and still in diagnostics mode and the knowledge that I seem to be gathering will sure make us experts on air suspension when (remaining positive) I manage to get it all sorted
Thanks for the link to the information sheets this is going to be really useful.
Denzil
20th Feb 2017 3:55 pm
trainmanone
Member Since: 19 Dec 2014
Location: stockport
Posts: 366
sounds like compressor is fubard........compressor not creating enough pressure .....
take it you have tried a rebuild kit ,I tried that didn't work ,got Dunlop compressor lasted six months motor dead ,put on amk without covers as only there to cut down on the noise as not water/mud prof.
no problems as yet
20th Feb 2017 4:08 pm
gstuart
Member Since: 21 Oct 2016
Location: kent
Posts: 13635
dabware wrote:
So i just sat in the car and put the IID on to see what was going on
The car is currently in access height so I started the engine and watched the pressure. This was at around 18psi then I selected normal height and the pressure increased to about 54psi in about 5-10 seconds and I got a ding then the compressor shuts off so the pressure then drops to 18psi in about the same amount of time.
I had a nose around the IID tool and managed to dump all of the air from the system and after running it for a couple of times it looks like no air is getting back into the system at all. I still have the air supply fault on the IID each time.
I am not stuck yet and still in diagnostics mode and the knowledge that I seem to be gathering will sure make us experts on air suspension when (remaining positive) I manage to get it all sorted
Thanks for the link to the information sheets this is going to be really useful.
Denzil
it seems the compressor is worn out , seeing its only providing such a low output
i did try and rebuild mine but replaced it in the end
check the air filter in the rear cubby box, making sure it's not blocked , take the element out then run the compressor again,
just in the off chance
failing it that it sounds like a rebuild or replace i'm afraid
unless someone else has other ideas
wonder if the reservoir valve could be blocked , or maybe the air tank leaking , so it doesn't build up pressure ,
amazing how much knowledge is gained by working on these, lol
20th Feb 2017 4:30 pm
gstuart
Member Since: 21 Oct 2016
Location: kent
Posts: 13635
trainmanone wrote:
sounds like compressor is fubard........compressor not creating enough pressure .....
take it you have tried a rebuild kit ,I tried that didn't work ,got Dunlop compressor lasted six months motor dead ,put on amk without covers as only there to cut down on the noise as not water/mud prof.
no problems as yet
same happened to me
i messed around for ages trying to repair the old one, then went for broke and bought a new dunlop , along with the new bracket and mounting rubbers
can't hear it any more when sitting in the landy
just got to fit the air tank , reservoir valve and silencer and the suspension will have been then rebuilt ,
20th Feb 2017 4:36 pm
dabware
Member Since: 02 May 2014
Location: Ashford, Kent
Posts: 9
Well, I got the spanners out and decided to do a bit more checking, I removed the pipe for the output and found I no longer have any pressure.
Removed the unit from the car and decided to take a look at the delivery valve to make sure it was ok. I did replace this previously however it now looks like the new one that I bought is looking decidedly second hand.
Looks like I will need to get an exchange item.
I will be purchasing a new compressor soon just glad I have a motorbike as reserve transport.
Denzil
20th Feb 2017 6:29 pm
gstuart
Member Since: 21 Oct 2016
Location: kent
Posts: 13635
that's the route i went down in buying a new one
expect u know already , but make sure u have new chassis clips that the bracket fixes onto
u need 3 x of them
i had to also replace my bracket as it had been broken on the corner
is amazing the difference after fitting a new one
fitting the new one, ref the covers, take out the insulation in the top cover, gives u more room
good luck
20th Feb 2017 6:52 pm
trainmanone
Member Since: 19 Dec 2014
Location: stockport
Posts: 366
if going to get the amk one without covers don't try to cobble the old covers to fit as they will vibrate like a tank ,ive got the amk one without covers and its fine,only reason for the covers is sound reduction as they are a water /mud trap .
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