Thread: Aircon 2016 D4 SDV6 - is this wear and tear?

Originally Posted by GregMilner

Just checked it again in the driveway. I can hear the compressor clicking on okay, cool air is fine on the passenger side of the car. But ambient temp on the driver’s side, both right front and right second row aren’t blowing cold at all. What th...?

I don’t believe what you heard was the compressor clicking on mate. These babies use constant drive compressors with variable displacement which is controlled via the displacement control valve I mentioned earlier. They don’t operate on/off like in the older cars.

Originally Posted by GregMilner

Just checked it again in the driveway. I can hear the compressor clicking on okay, cool air is fine on the passenger side of the car. But ambient temp on the driver’s side, both right front and right second row aren’t blowing cold at all. What th...?

As stated above, this is consistent with being low on gas. Despite the calls to "not turn it on", it's actually running all of the time, just at minimum displacement.

I'm going to go on my standard rant here, so those who've heard it before might want to change the channel :

The system relies on adequate gas charge to circulate the oil. They still operate adequately when they get low(ish), but by the time you've noticed any impairment in the cooling the oil circulation has been well below par for a good while. This is the reason that I recommend getting your systems re-gassed every couple of years regardless of how well they are working (and I'm not in the industry or sell refrigerant so I have no dog in this fight).

These systems are not hermetic. They do leak (from the day they are gassed up in the factory), and low refrigerant levels do cause damage. The systems with the rear A/C are even more prone as there are more joints and a lot longer pipework to hoard oil. People don't tend to notice impaired cooling on the rear evaporator while the dash unit is still working adequately and you've already started to trap lubricant in the lines/evaporators.

I did our Golf on the weekend. It was 2 years since the last go and it was 75g short. That's 14% down. Last time I did the D3 it was 25% down (after purchase, no idea of time frame) and was still cooling what I'd call pretty well. I did Mums Golf and it was 76% short after 2 years (and barely cooling). I think that one has a leak, so I'll have to get around to it shortly.

Originally Posted by DiscoJeffster

I don’t believe what you heard was the compressor clicking on mate. These babies use constant drive compressors with variable displacement which is controlled via the displacement control valve I mentioned earlier. They don’t operate on/off like in the older cars.

Thanks Jeff, didn’t know that. Certainly something makes a click noise under the bonnet when I hit the button, what would that be?

Originally Posted by BradC

As stated above, this is consistent with being low on gas. Despite the calls to "not turn it on", it's actually running all of the time, just at minimum displacement.

I'm going to go on my standard rant here, so those who've heard it before might want to change the channel :

The system relies on adequate gas charge to circulate the oil. They still operate adequately when they get low(ish), but by the time you've noticed any impairment in the cooling the oil circulation has been well below par for a good while. This is the reason that I recommend getting your systems re-gassed every couple of years regardless of how well they are working (and I'm not in the industry or sell refrigerant so I have no dog in this fight).

These systems are not hermetic. They do leak (from the day they are gassed up in the factory), and low refrigerant levels do cause damage. The systems with the rear A/C are even more prone as there are more joints and a lot longer pipework to hoard oil. People don't tend to notice impaired cooling on the rear evaporator while the dash unit is still working adequately and you've already started to trap lubricant in the lines/evaporators.

I did our Golf on the weekend. It was 2 years since the last go and it was 75g short. That's 14% down. Last time I did the D3 it was 25% down (after purchase, no idea of time frame) and was still cooling what I'd call pretty well. I did Mums Golf and it was 76% short after 2 years (and barely cooling). I think that one has a leak, so I'll have to get around to it shortly.

Didnt know that either Brad, thanks for the heads up, I’ll get it checked at my local LR indie tomorrow.

Originally Posted by BradC

..... system relies on adequate gas charge to circulate the oil. They still operate adequately when they get low(ish), but by the time you've noticed any impairment in the cooling the oil circulation has been well below par for a good while. This is the reason that I recommend getting your systems re-gassed every couple of years regardless of how well they are working ....... These systems are not hermetic. They do leak (from the day they are gassed up in the factory), and low refrigerant levels do cause damage. The systems with the rear A/C are even more prone as there are more joints and a lot longer pipework to hoard oil. People don't tend to notice impaired cooling on the rear evaporator while the dash unit is still working adequately and you've already started to trap lubricant in the lines/evaporators..

Brad, could any reasonable AC place do the check and re-gas? Or do you think it requires an LR specialist. Mine is 5 years old and no problems detected but this seems good advice to me.

Regards,
Scott

As mentioned above,when a system (any sort) operates, oil is constantly in circulation. That is why it requires a Miscible oil.

As my old boss/tutor told me in days of yore , "Imagine all the internal surfaces cut open, laid flat & painted with oil. That is how much oil is required in the system for correct operation" & if a rear evaporator coil is involved, obviously it will take more due to line lengths & routing. ie. low level traps. The same applies to gas charge.

I am not familiar with the system in question & it's quirks & ancillary components, but at the end of the day it is still only an enclosed recirc. system.


On commercial Refrigeration & Air Conditioning systems an Oil Trap is normally used which consists of a cylinder with internal baffles to capture vapour borne oil as the oil laden gas is passed through it from the compressor.

When this oil level builds up in the bottom of the oil trap, a float valve under high pressure opens & discharges oil back to the compressor low pressure side but that is strictly a Commercial system. No such thing exists for small systems to my knowledge nor would it appear necessary, & the High Side Float of yesteryear may very well have been superseded by some modern equivalent using electronics & other technology, but it was a simple system.



Basic Oil Trap.

Like so. Oil Trap.jpg


Now, what was the question?

Originally Posted by LRD414

Brad, could any reasonable AC place do the check and re-gas? Or do you think it requires an LR specialist. Mine is 5 years old and no problems detected but this seems good advice to me.

Any competent A/C place. It's only r134a and there is nothing special about the system in the Discovery. A competent one will weigh the removed gas so you know how much you were down before re-charging with the specified quantity.

Originally Posted by BradC

Any competent A/C place. It's only r134a and there is nothing special about the system in the Discovery. A competent one will weigh the removed gas so you know how much you were down before re-charging with the specified quantity.

Brad you're right, it was low on gas. I'm not familiar with car aircon systems, but from what the indie mechanic tells me, when he was running tests after regassing, the pressure "was getting up to 20 bar" which apparently isn't good, and indicated another problem, which was a sticking valve (I forget what he called it) that sits somewhere behind the dash. It eventually unstuck itself, so the system is working fine again now. However he did say that the valve in question may need replacing if it fails again - a tediously fiddly job requiring part of the dash to be dismantled - about 11 hours all up - plus about $600 for the part.

Cross fingers, it keeps itself unstuck for the foreseeable future:-)