I had to stop working on the air con for more important things in life, however now attempting to get it sorted.
My auto electrician is 55km away and while he is helpful, 1997 P38's don't form any part of his business.

All the work I have done so far has solved problems along the way but still I haven't been totally successful. So I have posted a long list of what I have done so far in the hope I can gain a bit more knowledge to reach the final goal of cold air in my car.
Compressor changed for one that was known to be operational.
Compressor clutch clearance adjusted to low side of specifications.
Land Rover wiring loom for early models added
Giving power to the compressor via a relay. No 10 in the fuse/relay box. 12.7 volts when last tested.
The known problem of corroded multi pin plug/socket cut out & cables soldered. Right side foot well.
Any connectors relevant to the air con operation cleaned.
Nanocom now showing YES to grant. So it’s talking to the engine module.

Aspirator Sensor for cabin temp. Removed from dashboard. Fan & sensor cleaned out, removed fluff.
Ambient Temp Sensor made using 10Kohm thermistor, piece of plastic conduit and thermal epoxy.
Heater Pipe Temp Sensor made using 30Kohm thermistor original plastic housing clip and thermal epoxy.
Receiver Drier Renewed.
Pressure Switch 2 (single switch) Renewed.

Took it into town to get Re gassed. Had to supply 12v to relay 10 to get the charge of 1200grms of gas into the system. Yes i know not the1250 grms but he stopped at 1200

HEVAC module still refused to activate Relay 10.
However supplying 12 volts to the relay proved the system was working … nice cold air.
But on a trial drive evaporator temp going down to 1,5 to 2 degrees, compressor clutch dropped out and fans activated. Evaporator temp went up and operation continued.

However I was warned that bypassing the HEVAC could possibly cause problems.
So the wiring bypass was removed.

Now just Fitted :-
Pressure Switch 1 (the trinary switch)
Evaporator Sensor Renewed.
On engine start up system would not operate the compressor clutch. So switched off.

Disconnected the battery for 15 minutes.

On re connection and start up HEVAC recognized everything and the on / off switch on the HEVAC will switch the compressor clutch on / off and there is no “book” symbol on the HEVAC panel, so its not reporting any problems.

Nanocom showing only one fault.
“32 Compressor Clutch Control Circuit Open Or Shorted to Ground”
Fault Type = Current.

Yet there is 12.7 volts at the compressor. Clutch can be operated using HEVAC ON/OFF button.
Compressor clutch clearance adjusted to low side of specifications. Done at the beginning of workings.

The smaller pipe out of the compressor gets very hot, larger pipe more at ambient temperature.
So NO cold air.

Blockage ??? Expansion Valve ???
I don’t have any gauges so guess I will have to arrange a trip into to town to my auto electrician.

Does anybody have any further ideas before I book in to my auto electrician?

The error you are getting is showing that the resistor in the loom isn't simulating the load from the compressor clutch. Pre-99 HEVACs drove the clutch directly and checked that sufficient current was being drawn so it knew that the clutch was pulling in. That is why the loom includes a big resistor to give a load to the HEVAC to keep it happy. If it detects that insufficient current is being drawn it will try to pull in the clutch, see that insufficient current is being drawn and immediately drop out. It will not try to pull the clutch in again until it has been reset by being turned off and back on again.

Later ones did not have the current sensing as they are only intended to pull in a relay so the factory versions didn't have, or need, the resistor.

If the evaporator temperature was going down to a couple of degrees and then the compressor clutch disengaged, did it re-engage once the temperature got up to 5 or 6 degrees? That is how it should work.

Don't fall into the trap that others have by misunderstanding what the AC Off button does. It does what it says it does, it turns the AC OFF. So if pressed with the light on that means the AC is OFF (the light is to warn you that the AC isn't working). With the button not pressed so the light is off, it means AC is ON.

Where did you find the info regarding a 30k Ohm thermistor for the heater core sensor? I read somewhere that it should be 22k and fitted one of those only to find it reads low so put a 10k resistor in parallel with it and it reads something like correct but in another thread somewhere that linked to a post on Landyzone, they said that a 10k Ohm would give accurate readings.

A hot small pipe but not cold thick pipe, suggests something not right in the refrigerant circuit but you need to be able to read the pressures to work out what. Have a look on Amazon, they are cheap enough, https://www.amazon.co.uk/TKSE-Diagnostic-Refrigerant-Functional-Refrigeration/dp/B0D6W9SC55/ref=sr_1_2_sspa just make sure you get one with the R134a port connectors or they alone will cost the same again.

I can confirm it is a 10k thermistor, not 30k.
I have made 3 of them now, and all good.

Thank you Gilbertd
I transferred the complete loom, resistor and all from my other car, now used for spares.
My compressor clutch pulls in and stays in for some time. The small compressor pipe gets really hot and it just appears to me it might build up pressure so much that the trinary pressure switch is activated and disconnects power to the clutch. It is at that point I switch the motor off.
I will have to get a gauge set to confirm that is happening.

Yes, in my hook up to power the relay 10, as the temp of the evaporator rose to that 5/6 degrees the clutch did re engage. I thought I had seen that somewhere but I have been looking up a lot of info and couldn't find it again. Thanks Just got to find out what is wrong that the HEVAC it's not doing the job for me.

No very early on in P38 ownership I realized the operation of the button. I only used it in the post to indicate that I could switch the system on/off and the clutch worked.

https://lr4x4.com/topic/109433-p38-hevac-sensors-replacementmodification/ is the site I found out about the 30kohm thermistor.
Using an infra red thermometer on the heater pipe the reading was pretty well the same as the Naoncom figure.

I was looking at a set of gauges offered by a car air con company here in Australia for AU$40 so will check for correct fittings. Thanks