saved from an earlier post:
Air Compressor posted by Greg French on 01/15/2005 10:40:57 PM:
Greg - I haven't made the conversion yet myself, but a Land Rover Master Mechanic gave me the following instructions for converting the air compressor to work as an air pump:
Yes, it's the stock compressor and tank. You just use a jumper wire with the correct sized pins to jump two pins of the EAS ECU connector[harness side with the big connector] or solder a jumper wire to the back-side of the connector/pins once you've taken the outer plastic housing off and exposed the inner guts. This wiring job allows you to use the "inhibit" switch located on the center console,'93&'94 models/or dash for the '95 Classic as your compressor "On" switch. The pins to jump with the wire are pins #8 and #29. Pin 8 has a yellow/blue wire going to it, and pin 29 is a grey/yellow wire. With this, you're directing 12 volts to turn on the compressor relay instead of the old, now missing ECU via the middle EAS switch[inhibit switch] You must plan on installing some type of safety though for the system, as you can't use the old pressure switch which used to be the ECU's clue as to when to turn the compressor off.
I handled this in two ways, first I use an air hose that has a psi gauge in-line in the hose, so I can keep an eye on the system pressure. Second,I mounted a relief valve that blows at 150 psi where the stock tank mounted pressure switch was, you don't have the fitting on your tank as LR moved the switch over to the valve block for '95 and later RRs of both body styles. So, you can plumb in a tee fitting with a reducer bushing for both the coupler and a safety valve at the end of the tank with its 1/2" pipe thread plug, or add a different type of pressure switch that goes open when you reach the max pressure, and wire the new switch into the existing compressor relay under the passenger seat to open the ground circuit when max pressure is reached.
In case you're wondering why you can't just use the old stock switch, LR uses a switch that CLOSES with the high pressure limit to signal the ECU, and this is harder to wire into the system for what we want with the ECU now out of the picture instead of them using the more common switches that would go OPEN and stop a system from operating when max pressure is obtained!