Air Supply for ARB Diff Locker & Tire Inflation, P38
Hardy Neale's Approach

air parts
Parts Required
Design and Procedure
More Information

A useful upgrade for serious off road work is an ARB air locker. This requires an air supply, so on late model Range Rovers it is possible to use the stock air pump rather than installing another one as is necessary on most 4x4s. Hardy Neale took advantage of the occasion of installing his locker to set up his system to supply on-board air for tire inflation. 

Hardy reports: "The ARB locker requires an air supply of no greater pressure than 105PSI.
As the EAS runs up to 150PSI, some sort of regulator was required to protect the locker and to supposedly stay within warranty guidelines.  Now was also a good time to sort out some on board air using existing EAS reservoir, so this is what I came up with..."

Parts Required
The picture at top right s
hows some of the various components Hardy used - clockwise from left:

    6mm plastic T-piece

    1/4" threaded brass T-piece (2x6mm & 1x1/4" fittings)

    SMC regulator with gauge and 6mm fittings

    1/4" fitted inflation valve (150PSI+)

    2nd gauge

    6mm fitting with 1/4 thread (for 2nd gauge)


Design and Procedure
"It took some time to work out how best to route all the different air lines and to locate all fittings.
Using a 6mm T-piece I intercepted the main supply line from EAS up near the main valve block.
The new line then went to another T-piece, creating 2 additional supply lines - 1 to main gauge and 1 to brass T-piece.The brass T-piece was required to accommodate a 1/4" push in fitting - the size of the line for the main inflation valve. The other 6mm line then went to the regulator.

NOTE: Never fit 6mm line into a 1/4" fitting and never fit 1/4" line into a 6mm fitting - they are not interchangeable."

The pictures below show the general approach.



The light blue line is for rear air locker (5mm) and dark blue line is for main inflation valve.
The orange fitting is the ARB 5mm fitting.

Note 2 shiny bolts on power steering fluid reservoir - later replaced.

Picture showing location of brass T-piece within EAS container - no need to mount on any bracket, sits there quite nicely.

Note in the above pictures you can see a cluster of 4 external solenoids (to left of EAS valve block in left hand picture and at top right in right hand picture). This is for the systemHardy had installed earlier for cross linking front and rear suspension in the same manner as the new Mk III Range Rover. Note also various 6mm T-pieces at valve block used for cross linking suspension.  Hardy toyed with using these solenoids for rear locker but soon realised the ARB 3 way solenoid is required to properly de-activate diff lock.

previously unemployed piece of hefty aluminium angle loitering in my shed soon found itself a well paid job. Fitted hard against the radiator frame and held in place by slightly longer bolts to power steering fluid reservoir, it supports the regulator, 2 gauges and inflation valve assembly. The whole assembly does flex a little laterally - but this stems from the radiator frame, not the installation method.



Installed Assembly.

Picture showing the actual tyre inflator with 25' coiled hose and simple lever style connector.

"In the picture above left, on the LHS is main inflation valve. This can be used to de-pressurise and re-pressurise EAS reservoir as well as just re-inflating tyres! 

LHS gauge shows the pressure in EAS reservoir. Handy for monitoring pressure when filling tyres. Picture current pressure is 135PSI.

RHS gauge shows regulated pressure for air locker, set to 95PSI. Note black locking knob on RHS to adjust pressure.

The ARB solenoid in the middle was a bit of an after thought. I was in a hurry as I'd run out of time, but 6 weeks later the double sided tape is still holding!"


So far I have not been 'let down' by the inflation system.

While it's no powerhouse, the existing compressor & EAS reservoir is adequate for 'topping up' tyre pressures after partial reduction for rocks and sand etc.

Best part is the comparatively low cost and relative benefits.

More Information
An alternative means of tapping into the air supply for tire inflation and other tasks is detailed on the "air supply for tires and tools" page.
More information on Hardy's system of cross-linking the air suspension appears on the air suspension cross linking page.
More information on the Air Suspension system appears in the Air Suspension Operation, Diagnosis and Repair section




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Page revised February 10, 2012