First time I really needed it this afternoon on a long run down the M6 / M1. The cooling was switching between periods of cooling and not cooling. and wouldn't maintain a comfortable temperature. When it was cooling it almost felt too cold like a very old AC system that just has an on and off switch. Before I take it to a garage any pointers? 2012 TDV8 Vogue (L322)

you should have your Aircon on most of the time as it keeps the seals moist and sound. it also removes water vapour from the air inside. (A/c can also be used for heating)

did you have the auto button on/illuminated?

I understand over-filling can cause those symptoms. That said, I once had a 5 series that did it and could never get to the bottom of it. 2016 Skoda Octavia VRS Estate
<gone>2009 FF Vogue TDV8 Buckingham Blue</gone>
<gone>2015 BMW 520D SE (not my favourite car)</gone>
<gone>2009 D3 HSE Galway Green</gone>

It's always on (Auto). Never had to deal with this amount of heat before so only noticed the cooling not working continually. 2012 TDV8 Vogue (L322)

First thing to do with any aircon issues, is to recover the refrigerant and compare to the specified charge weight. 10-15% under is acceptable for a system not recharged within 2-3 years and rarely used.
Your issue does sound like a problem with the refrigerant control valve in the compressor or possibly a blocked condensate drain causing the evaporator to freeze up.

If you set the climate control to 20deg. C. for example, with the interior at, say, 25deg. C. (and on full auto) the air would have to be significantly colder to reduce the interior temperature so could therefore feel 'cold' until the interior temperature was approaching the setpoint, where it would 'level off' in terms of air blend temperature and fan speed. If for some reason, the refrigerant ceased to cool, then when it resumed, the process would start again.

Also if I set the temp to minimum the air from the vents is not 'that' cold. Maybe I'll try a regas and take it from there. 2012 TDV8 Vogue (L322)

If it needs a recharge and it's been in regular use, then there's a leak. It's illegal to recharge a known leaking system, whoever does it can be liable for a fine of up to £5k and lose their F-Gas certification - Enforcement is another thing however....

Do you have diagnostics that can read the evaporator temperature? if so, set the temperature to something reasonable, check the exterior and interior sensor values make sense and run the engine and aircon on auto, as long as the evap. temperature drops below 7deg.C and more-or less stays there, i.e. doesn't suddenly rise to 10 degrees or pendulum wildly between 4 degrees and 12 degrees for example, then the issue isn't within the refrigerant circuit.

Last edited by Phoenix on 22nd Jun 2022 8:38pm. Edited 1 time in total

I'd presume a reputable garage would pressure test the system? 2012 TDV8 Vogue (L322)

Always check, never assume they *should* however, not all will due to time constraints or unwillingness to get involved... to be fair, aircon leaks can be so small it takes months for the charge to drop enough to show a defect - something that wouldn't show up in the standard 30 min vac / pressure check, the 'sniffer' I use will detect (apparently) a leak that gives a loss of 4g in 12 months - and that's not the best one available, sometimes it needs a UV dye to be added and booked in for a check in three months with strict instructions to not jetwash the radiator area of the vehicle....

JayGee wrote:

First time I really needed it this afternoon on a long run down the M6 / M1. The cooling was switching between periods of cooling and not cooling. and wouldn't maintain a comfortable temperature. When it was cooling it almost felt too cold like a very old AC system that just has an on and off switch. Before I take it to a garage any pointers?

From my post earlier - it's not capable of providing ice cold air at any time. It's at best 'chilled' 2012 TDV8 Vogue (L322)

"When it was cooling it almost felt too cold like a very old AC system that just has an on and off switch"

It'll most likely be your compressor. 2015 Range Rover Autobiography 4.4 SDV8

Last edited by garyRR on 22nd Jun 2022 10:27pm. Edited 1 time in total

Christ - you're good - if only I had your insight and balls of crystal not gristle, I could have forgone all those years of training and experience, being able to definitively diagnose over the interwebs is a skill indeed, I take my virtual hat off to you.

Not going there. If you're bored and looking for an argument, please go elsewhere.

I note you have a 3.6. The 4.4 has a known issue with the RCV on the compressor and is the cause of most A/C problems, which the 3.6 does not. JayGee has a 4.4 TDV8 and was reporting exactly the same symptoms I had.

Speaking from experience having just gone through all these steps, and sharing it to help out another forum member to save time and expense is what the site is about, not criticising other users. 2015 Range Rover Autobiography 4.4 SDV8

See my first post which mentions 'refrigerant control valve'. It may surprise you to know that people have knowledge which extends beyond their own vehicles...
Without direct measurements, it's all a best guess though, isn't it? We have a service receptionist that has an almost clairvoyant ability to pre-diagnose faults, all because 'my boyfriend is a tech, you know' although not a very good one and works 30 miles away on a completely different brand, but still.... it gives her some sort of edge, apparently.

Your experience could well be someone else's blind alley, I wouldn't recommend your solution as a fix due to confirmation bias. each and every problem needs it's own solution.