When delivered from the factory, the P38 AC coil, is fed 12v from the HEVAC controller. This 12v compressor feed, goes via a pressure switch (- which turns off if pressure is too low or too high). For the early GEMS models (95-99), the AC compressor also has a 'thermal trip' built into the compressor, which cuts the power supply to the coil, should the compressor get too hot. On the later Bosch models (99-02), the AC Compressor has a pressure bypass instead of the thermal switch.

There is a wiring loom available from LandRover, which alters how the AC coil is supplied power. Instead of power coming from the HEVAC unit, the HEAVC switches on a (new) relay which switches battery 12v directly to the coil. By powering the AC coil this way, you can get way with larger clutch gaps at the compressor. I suspect that the LR engineers were given a task to sell a new wiring loom, rather than fix/adjust the actual 'wear' issue on the clutch plates. If you use this extra loom, you end up with an extra relay in the engine bay fusebox and this change is quite expensive. If you should want to make up your own loom to do the same thing (for far less money), be aware that the HEVAC controller, will disable AC coil output if the current along that wire is less than expected. I.e. you can't just put a relay at the end of the wire that used to connect to the AC coil, you need to put in a 'dummy load' in parallel with the relay-coil, by using enough big, high power, resistors, to simulate a 40-50 watt load (= about 4 amps!!). Make sure you don't go above the power ratings for the resistors you use - otherwise fire is not far away!!

The full Workshop Manual and ETM (Electrical Troubleshooting Manual) for the vehicle is called "RAVE". If you are keen on looking after your car yourself and understanding what is going on, then RAVE is invaluable. RAVE is available for free download from: RangeRovers.net :: View topic - Rave in Acrobat 8 - Ready To Be Downloaded

For me, I've just discovered (today) that my AC coil is not closing when it is hot, even when it is supplied directly with 12v. The clutch gap turns out to be about 0.9mm. According to the specifications clutch gap is supposed to be 0.6-0.8mm. This will have been the cause of my intermittent AC issues for the past 3/4 months (- especially when the weather is really hot and everything expands slightly). Tonight, I will be following the procedure in the link below, to reduce the air-gap of my AC compressor clutch:
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This I expect to fix my AC issues.

BTW, my P38 is a '97 4.6 with 131,000KM (81,000 miles).

well its not only Landys but its also mercedes, Rolls royce that i know.

Kevin Grimley said:

you would of thought land rover would of always done it the conventional way, switch on, light on, but no. I would love to meet these people at Land rover who come out with such ideas. I had one some years ago, fit heating elements in the front side windows, instead of the dam steering wheel, saves you scraping the window to look in the mirrors. Now that they have read this, some clever dick at Land rover will say "what a good idea"

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