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  #1  
Old 02-25-2019, 06:36 PM
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Twin axle air - known good figures ?

Hi guys


Starting to chase a twin axle air suspension issue - I know that first im going to be checking for leaks and then refurbing the compressor due to code 74 (filling requested but no increase in pressure).


My question is more to get a list of know good numbers for myself and others to use to help check their system more accurately hopefully


So for a good working system does anyone know a standard working pressure reading or an acceptable limit ? Im seeing roughly 160 - 200psi through a friends scanner and no sagging over night so im curious what triggers the code.


Also what are acceptable deviation measurements before a height issue is triggered ?
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Old 02-25-2019, 09:54 PM
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Sag will be a different problem the error you are describing is pressure tank side.

I thought I recalled 160 being the normal pressure so the 200 actually sounds too high almost like the high cut off switch is not doing Its job.

When pressure gets low enough say 150 psi it should request a fill and fill up to say 170-180 then shut off. If I'm correct the normal fill cut off is not shutting down the fill (and is also how the computer knows it's full) it never gets the full signal. Keeps filling until the overfull sensor stops the pump.

A bunch of "hunch" above. Dig into the function of how It decides to start and stop filling and the actual cut off pressure.
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Old 02-26-2019, 04:34 AM
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I did some digging over night and found some documents with some numbers in them :


Max pressure the compressor can make is 300psi
Operating EHC2 pressure is 225psi with an allowance of 10psi above or below that.


I checked mine for cold this morning and the vehicle was pretty even and had 200psi in the tank before starting.
Started it up, let it self level, raised it, lowered it etc and max pressure I could get was 200psi with the compressor at 78degrees.


Going by those numbers that I found im no too far off however it may be the time its taking to make that pressure !


Next step is to rebuild the compressor and check for leaks. Then I will know if the system is air tight and I may find damage inside the compressor etc
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Old 02-26-2019, 09:31 AM
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Sounds like time for the rebuild kit. Worn seal will cause your symptoms.
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