So, my a/c compressor has a slow leak around the seals (green/UV oil gets spun off the clutch). So i decided to fix it...I have a replacement compressor (long since gave up on the hope of finding a seal kit), a new receiver drier and bunch of metric green o rings... The replacement compressor is pre-dosed with PAG oil.
Can I just bolt the new bits on and change over the pressure switches and then take it somewhere to have the ac evacuated and filled? Instructions with the compressor talk about having to flush the system etc etc - is that really necessary? Then I would need to find an ac fitter and the whole job becomes that much more expensive/ time consuming

Tnx in advance for the advice, Rob

The only time you would need to have the system flushed is if you had burnt out the old compressor so you need to get rid of the contaminated oil. A mate, who owns a soft dash Classic LSE and is the other half owner of the Vogue we've been returning to it's former glory, is a mobile AC engineer. You're a bit out of his normal area, but if you fancy a run up to Cambridgeshire (we're a tier 2 area), he'd be able to sort it for you.

Tnx Richard...we're a 4, although maybe you will be too soon?
I'll just crack on with it...gives me something to do on Boxing Day

Yeah, we become a 4 as of Boxing Day too so that's screwed travelling for me too for a bit. My hose from compressor to condenser has started showing signs of leaking where the alloy pipe joins the hose so I've got one of those on the way and was intending to have a run over to his when it arrives. We could recover the gas, change the hose then vac and refill it but the restrictions mean I shouldn't drive over to him to do it.

Booked in for a recharge tomorrow with ATS....when I went in on the 24th ATS evacuated the system for me. The compressor today was an easy switch - receiver drier was a little more time consuming, mainly because i dropped the bumper off. My Toolzone green rings, although metric, were not much use for the receiver drier - looks like you need 8x2 on one branch, and 8x2.5 on the other, but hard to be sure

I have mixed results getting the a/c to work straight after recharge at the best of times, usually needs a bit of a run... but when it's winter outside you actually need to select Hi to warm up the evap sensor enough to then be able to select Lo and get the ac running. Probably obvious to everyone except me (and the bloke at ATS).

At least it didn't leak though, that's the main thing

As the temperature is slowly improving my thoughts turn back to a/c. The clutch doesn't kick in, which i think is electrical. The clutch kicks in fine with 12v jumped from the fuse box and also with a 9v battery (who knew ? draws alot of current though). The thing is, if I measure across the terminals of c166 (round, male a/c connector) I see 12 volts, and I can see it at any ignition position - but it's not enough to draw the clutch in... I'm pretty sure that this should read zero until the engine's on at least. So I'm a bit puzzled why I see 12v when I don't expect to, and that the 12v doesn't pull the clutch in... I'm guessing something has failed/ a wire is damaged...next stop trinary switch and pin 7 of the C102 connector, unless anyone has any other thoughts?
I was thinking of knocking up a harness with a relay in it to take a positive signal from the dual pressure switch and then use a fused 12v supply to power the clutch. I think there was an official harness to do this - ie for the earlier P38s where the HVAC ecu is expected to power the clutch directly... does anyone have the official diagram? Not v difficult I suppose - I just need to route a live feed in for the relay, and find a couple of those round a/c electrical connectors

What's the air gap on the compressor clutch like? Mine was well worn and too wide (it should be between 16 and 30 thou) and the feed from the HEVAC goes through the notorious multiway connector in the RH footwell (as well as via the Trinary switch), so a combination of a wide air gap and a bit of resistance in the connector and it wouldn't kick in. I tried putting a relay in place so the coil would be energised from the HEVAC and switch full battery volts but that won't work on an early HEVAC. It looks at the amount of current being drawn and if it sees a lower than normally expected amount, it assumes a problem and doesn't try to energise the relay any more.

Tnx Richard, gap's good, measured with a feeler gauge. Will try the RH kick panel connector for sure

V good to know about the HEVAC programming for current draw, so I shan't waste my time on the relay option.

I measured the resistance from pin 7 at the RH kick panel through to the positive at the round plug for the a/c compressor - which is negligible (it was 28 ohms before i jetted pins1/7/12 with contact cleaner). I no longer get a ghost 12v signal at the condenser (which was there at ignition off, too),. After I cleaned the RH connector the clutch even kicked in for a couple of brief moments, so i think my issue is that one or more conditions for grant and request via pins 1 and 12 are not being satisfied.

I'll keep looking tomorrow, but does anyone have a detailed systems document for the HEVAC ECU - with a list of the conditions required for a/c grant, and request Rave is a bit vague, so I'm looking for the next level of detail My sensors all look to be reading fine. Temp is at Lo. Engine on

In the last couple of weeks (after i tried to calibrate the blend motors, in fact) my distribution flaps have frozen at 83%. I can't really be bothered to free them up at this point, unless we think that that would be enough for the ECU not to apply a/c? So it does have a service book symbol, which registers during the blend flap test cycle at start-up - so most likely the distribution flap being frozenas opposed to anything else.

I just saw today that the GEMS ecu reports that the AMFR correction is at the maximum positive value, so MAF may need a clean, but I assume that's unconnected

Cleared the distribution doors error (was a stiff mechanism) - now back to just "a/c compressor circuit open" which is not true - as I measured the resistance manually as I mentioned above. I can read on nano that GEMS ECU is receiving an ac request, until after a few minutes of engine running and set at LO, and then it shows the book symbol.

I wonder if this has to do with the ECU determining that the resistance of the circuit is somehow out of spec. I'm still holding out for an a/c systems document, if anyone has ever seen one. I have an EAS one, that is more detailed than rave, i thought there might be a hevac one too

Hi Romanrob, the kit for the additional relay Haus the part number YMQ104590AA.
I don‘t have the pdf / tsb here, where I am writing right now, but of You do a google Image search with that part number a wiring diagram shows up on the „landyzone“ website.
Or You have rave with tsb and search for the bulletin?

Edit: found a link to the pdf when I entered the part number above and pdf. Here You go: https://www.rangerovers.net/attachments/06-10-99-intermittent-operation-of-ac-system-pdf.235530

Super reference KCR, thanks for that.

I dug out the HEVAC unit the other day and it turns out I have JFC102550 which as far as I can make out for my car (a 1998, chassis 395xxx) was the "wrong" / later model (it's been there since I bought it 3 years ago). I'm thinking through the implications of that before I make my next move. At the ECU I can see Request (Low/0.7V on a 12v line) and the incoming Grant (Low on a 5v line) but after a couple of minutes the HEVAC gets bored, service symbol comes on, and both lines go high. So far I have not been able to detect any voltage on the black/ yellow pin at the HEVAC ECU. I pulled apart the ECU the other day and there was no visible signs of corrosion or damage. So I'm just trying to work out if something has failed in the ECU, or there's some other condition not satisfied.
Having cleared the distribution flap jam the other day, HEVAC now reports a short to front windscreen (despite me having pulled both the fuses and relays)...I can go chase that next... but I assume that is not linked to a/c not working.

I wonder if either the fusebox or HEVAC ECU are messing with me?

Sounds like the HEVAC has been swapped at some point but it shouldn't matter. The main difference is that a later one doesn't flag an error if it only sees a low current being drawn when trying to pull the compressor clutch in as it is expecting to just be operating a relay and not the clutch itself (but it is only a firmware change to stop it flagging an error, it is still capable of operating the clutch directly). It's the other way round that won't work, an early HEVAC needs to drive the clutch directly and not with the relay. Short to front windscreen is one that seems to appear at odd times but will only flag an error if you switch the heated screen on, under normal circumstances it won't bring up the book.