Dropped my car down to have the AC regassed and just had a call to say they haven't done the regas.

They checked for power at the compressor first (as I said it's not kicking in) and they said there is no power to it. They checked the fuses and relays and said those are fine.

I asked if they were able to confirm if the system had gas in it with a pressure gauge bit they said they don't know. Their machine doesn't measure the pressure of the system. It just tells them how much gas it was able to suck out when they evacuate the system - which they didn't do as there was no power to the compressor.

I'm not sure if I'm in the same situation that Romanrob is in with his as I'm fairly sure my Nanocom said "yes" for AC grant last time I was poking about with it.

What conditions need to be met for the AC compressor to be sent a power signal?

1) AC switched on
2) Cabin temperature measuring higher than the temp set in the HEVAC control panel
3) ??

Does it look for a reading from a pressure sensor to make sure there's gas before firing up the compressor?

Doesn't sound like they know what they're doing. The machine will have gauges on it - I've never seen an automated machine with no indication of actual pressures even if they are meant to be idiot proof.

There won't be any power to the compressor clutch when there is no gas in the system - as the trinary switch low pressure cut off prevents the clutch engaging by breaking the circuit, to prevent the compressor engaging with no gas to move oil about the system and causing damage. It's wired in-line with the clutch, so it won't report back to the HEVAC or log any codes etc because the gas as escaped*. Chances are, its got no gas, or if it has, the trinary switch has perhaps failed.

I'd go somewhere else to start with - if they don't know why their was no power to the clutch without checking pressures, they haven't got a clue.

I can dig out the trinary switch pins to bridge if you want to check the clutch for operation etc.

*One exception - on early P38s, the HEVAC provided power to the clutch (through the trinary switch) directly, so if the system was low on gas/empty and the low pressure cut off was activated, the circuit was broken to the clutch. Because the HEVAC on these earlier models could 'see' the load/current draw of the A/C clutch, it could detect if the load was missing and throw an 'open circuit' fault on the compressor output. When this changed to drive via a relay, which draws much lower current, the error detection was programmed out. Yours will drive via a relay, and thus the error detection won't be present. Unless of course someone has swapped in an early HEVAC controller for some reason - in which case you'll find the open circuit fault for the compressor output with a nanocom. This aside, gas or no gas, correct or incorrect HEVAC, take it somewhere else.

Oh one more thing - as I'm not F Gas certified yet I had to have my RR filled up by someone else recently after the condenser leaked. I took it to my local F1 autocentre. Picked it up and was told 'oh, we've underfilled it a bit because its an older car and its a lot of strain'. For the price, I wasn't too fussed at first. But then I realised, the 1000 out of 1380 grams the Thor setup is meant to take is quite a chunk missing... and it was hissing in the evaporator really obviously, as they do when low on gas. Made them fill it properly, because frankly, the 'strain' is bullshit, and I've paid to have it filled.

The guy gave me the receipt that the machine printed out for a second recovery and refill operation... which I don't think he realised showed what it extracted - 627g. Not even close to the '1000' he supposedly put in. I know r134a is getting expensive, but I don't give a toss - I've paid to have it filled and to work properly.

The p38 takes a lot of refrigerant - if the place you go to doesn't specify that they charge by volume/weight, make sure they fill it properly and don't try to screw you over.

Hear Hear!
To be fair, I've had great results from Kwik Fit.

As Sloth has said, if there is no gas in it, there won't be power to the compressor as the supply goes via a pressure switch. They should evacuate it, start filling with the engine running and the HEVAC set on Lo on both sides. The compressor will kick in as soon as there's enough gas to get the pressure up high enough and then continue filling until the amount they have set has been reached.

Cheers, pretty much as I expected - and said to them when I dropped it off!

They said they didn't go as far as hooking up to the regas machine because there was no power. Need to solve the power issue then they can regas. It was weird.

Sloth, the bridging info would be good. Thanks :)

They're a local LR specialist and came very highly recommended by several people in my LR club. They fixed the gearbox and crank pulley on our Freelander and generally seem to know what they're doing. I guess whoever was working on it today was having an off day.

I'm sure that when I took mine to be regassed (ok a couple of years ago now, so my memory might be a bit hazy) the guy who did mine filled it without the engine/compressor running.

He used to work for BMW but did bits on his own now, and had all the kit to refill AC properly.

He nitrogen checked for leaks, and then vacuumed the system down, followed by a fill of the correct weight of r134a and oil, and then I started it up and he checked the operation. Compressor kicked in straight away and nice cold air.

I might be wrong on the running engine whilst filling, but I don't recall there being any issues or "ooohh this bit isn't triggering so we can't do it".

I am amazed at what shit some places come out with... I remember taking mine into a specialist place for adaptive values to be reset on the engine ECU to be called 4 hours later to be told that they didn't know what they wanted me to do... Their diagnostics was out for repair and they weren't allowed to touch my engine because it had LPG on it.

Get that certification, Sloth, and the we can do an AC camp! ;)

When I had mine done (twice) by the local National Aircon people the young lady doing the job also didn't run the engine during filling. She just evacuated the system, did the nitrogen check for leaks and re-filled it. The we started it up and verified that it came down to temperature as per RAVE. She said it was interesting to have the official manual to do the right checks.

Also reckoned that underfilling is bad for the system. Told me that on an older car its a good idea to do a re-fill every 3 years or so even if the A/C still seems to be working OK as an older system will very slowly loose gas.

Not impressed by Halfords, Kwikfit or garages with a machine in the corner and a certificate on the wall. Guaranteed underfill. Especially on a high volume system like the P38. She said that frequently you just get a standard amount shoved in, maybe choice of small system or large and thats it. Certainly when Halfords did mine the first time they under-filled it as the fill lasted about 6 months. Her full fill lasted about 18 months and confirmed I had an intsy bitsy teeny weeny leak that wasn't properly showing up under test. But the fill had the UV indicator stuff in it so sufficient traces were left to confirm a leak.

Clive

Hooked it up to the AC machine at work today - completely and utterly empty. The pressure gauge didn't even flicker.

So, looks like there's a leak despite it holding both pressure and vacuum each time it gets regassed.

Time to get it refilled somewhere and then check for leaks - hopefully it's something easily replaceable.

Arranged a regas at work next work but I'm wondering if it's worth me replacing all the o rings while it's empty.

Would a set of generic AC o rings do the job or are there any oddly sized ones?

i had mine gassed last year and it all leaked out of the o-rings on the compressor, and those two are very easy to swap.

I think it's worth doing the o rings, but having said that I got away with replacing the condenser and drier last year and using the same o rings. My air con was regassed today, but was at 6 bar prior to evacuation/ recovery so seems to hold pressure pretty well. The o rings are different sizes (and green, obv) - maybe check on lrcat.ru and have some on hand just in case one/ more are trashed

I've just had a look at LRcat. It lists a bunch of o-rings in the sections for the AC pipes but doesn't show where each one goes or how many of each are needed. 7mm, 9mm, 11mm, 14m and 17mm.

There's kits on eBay for around £6.00 with hundreds of green HNBR o-rings (https://www.ebay.co.uk/itm/270-Piece-Air-Conditioning-O-Ring-Assortment-Kit-Green-Air-Con-18-Sizes-UK/401768875544?hash=item5d8b4a8618:g:BGkAAOSw56Jc3uPA&frcectupt=true) but they don't seem to have 7mm and 9m.

Any idea how precise the 7mm and 9mm measurements from LR are? 6.8mm and 8.8mm are quite close.

For the comrpressor o-rings LRcat lists STC3176 and STC3177 but only for chassis numbers up to WA410481. Does anyone know the dimensions of these? LRcat doesn't list them. The part numbers aren't prohibitively expensive but when I get 270 o-rings for £6 paying £7+ for each of these seems a bit excessive :P

This diagram and annotations might help sort out what goes where : https://www.roversnorth.com/category/696_range_rover_p38a_99_02_heater_air_conditioning
Not the easiest to interpret or read but combining the picture, numbers and the listing should get you there.

When I did my condenser I found a similar but better one somewhere else. Thought I'd downloaded it but seems to be lost in comouterspace at the moment.

I got one of the E-Bay green O ring kits but ended up buying at least some official Land Rover ones. Probably from Brit-Car. Don't recall which ones. Of course my kit might have been different to the one you are looking at anyway.

Past my bedtime. I'll have a look tomorrow.

Clive

The O ring kit I have is by Toolzone, part number HW019. I was sure that I bought at least one original O ring from BritCar when I did the condenser and drier change back in 2016 but, unusually for me, I can't find any records. Obviously being sloppy then as even the condenser itself isn't in the Excel expenditure file for that year.

I bought one of the generic O-ring kits from eBay a few year ago as the Thor part numbers are a mess and I couldn't figure then out.

That and I resented the idea of paying £6 or £7 each for a couple of O-rings in the hope they were the right ones.

I found that the various size kit didn't have exact size replacements, but there were ones close enough ( I went a touch smaller, so the stretched over the RR fittings a bit more where I needed to). Since doing the condenser a couple of years ago (the last time the system was empty, vacuumed, refilled etc) it's been fine and leak free. Had the AC on the other day and it was still getting nice and cold, so I obviously haven't lost too much gas!

I think I'll just get the set of hundreds then!

Marty, did the set of lots fit the rings at the compressor end as well?

Did they change the compressor for Thor vehicles? The part numbers (STC3176 and STC3177) for the compressor orings seem to be GEMS specific.

LRcat only lists those two.

Surely anyone working on car AC systems should know the clutch won't come in if a pressure sensor reading / switch reflects very low pressure.

I too have had AC specialists try to fob me off with under filling systems and made them put in the full correct amount. I think just about every car I've had with AC (which is just about every vehicle I've personally owned since about 1989) has had a plate with info on how much gas the system should hold... But it seems AC gas capacity data supplied to chain store type AC centres is often a lower figure than the figure on the plate - so particularly in larger/chain AC companies it might not be the technician that's trying to fob people off, it might be the firm's policy to save money by underfilling systems and the technician might be unaware.

Sloth, what are your thoughts on the DIY AC refill kits from e.g. Halfords? They have a pressure gauge and you're supposed to get the LP side pressure reading 'in the green' on the gauge... Is reading LP pressure a reliable way of knowing if the AC system is properly filled? I've used them plenty times especially for top ups and they do work but I'm always left wondering about if the system is under/over filled.

Also, can you use propane in R12 systems?

The trouble is with places charging a flat rate of say £50/fill regardless of car, is that most cars take 6-700g... then we rock up with a P38 needing 1200-1380g. Suddenly they're barely making any money taking cost of gas and their time into account. At the same time... that's not my problem.

The DIY refill things I'm not a massive fan of because in the UK, they can't legally contain actual refrigerant anymore. So long as the pressure on the low side doesn't end up massively high, it should be okay. But it can't beat weighing it in. Equally.. if the system is empty and has air in it, you're filling a system with an unknown 'refrigerant' as well as the air, which will have moisture in it and emulsify the oil... all ending in a mess. Pressures probably all over the place too. Then you have those with 'stop leak' additives in, which I've seen quite a lot of stories of TXVs being blocked up as a result, needing evaporators pulling out to replace etc.

I'm not sure on the R12 idea - I believe propane is mostly compatible in properties with R22, and R290 is basically just propane with a very low moisture content. Just has the slight downside of the old flammability issue... although the new R1234YF is too, so I guess car manufacturers aren't that bothered. I know a lot of us drive around with LPG plumbed up all over the place, but to me you're much more likely to end up with a big leak on a condenser when a nice pointy stone hits it or you have a collision with something in front....

Thanks Sloth, raised my eyebrows with DIY kits in the UK aren't allowed to contain actual refrigerant - I have charged completely empty AC systems using DIY refills and they've worked so obviously the gas contained in the refill was refrigerant of some type?

Knowing what I (think) I know now if I still ran cars that used R12 I'd fill them with LPG (propane) and probably see what I could come up with regards compressor oil. Back in the day when AC in the UK was fairly unheard of I used the services of several AC specialists, visited them at their homes, they probably only usually worked on commercial systems since hardly any cars had AC. Filling quantities were guestimated (except for the sight glass) and it was expensive but propane would have been cheap. All the specialists also seemed to over stress the dryer needed changing and would have charged about £700 for that lol, I never changed a dryer and never had a problem.

I haven't looked into what any of them actually contain - but it won't be r134a, and some even state as such its a 'compatible gas' - if it works, then great.

Changing the drier is like changing the filter when you do an oil change... you can leave the old one on and it'll run fine, but it won't do the job like it used to. Aluminium oxidises and corrodes, and most a/c systems are made up of a lot of it. So over time you have the risk of internal corrosion floating around and blocking the TXV etc. That said... I haven't always changed it, and I haven't had a problem. On my E60 530d, the drier is actually part of the condenser... presumably for cost and space saving reasons - but it means when it inevitably gets stone holed and needs replacing, you get a new drier automatically too. On the other hand, I had one of the discharge pipes rub through on body work and vent the precious gas :( I replaced the pipe, vacced down and had it filled - I'm not changing the whole condenser because of that... Sure, it won't work as well as a drying agent, but I left it vacuuming for hours to hopefully boil off some of the moisture the desiccant would have absorbed.