D4 AirCon issues

[terry1738]

Good day. Air con started playing up a few years ago wouldn't come on for about 5 minutes gradually got worse and now it works only when it wants to. When its working its great but I would prefer that I control it rather then it decides when to work. Had it looked at and gas was full was told its the compressor but cant be that as it works fine when its decides to work.
Just changed the pollen filter because when I opened the window the air con started to work so thought the change in internal air pressure was causing it (wishful thinking, of course no improvement) so thought maybe temperature sensor. I also saw a land rover notice some valve on the compressor cause an intermittent problem .
What do you guys think , should I go with changing the compressor or maybe find someone who will diagnose the valve which is $50 and I think is accessible from the LHS tyre well or is there something else I can check and replace.
I like to do stuff myself and changed timing belt and manifolds but am a bit stuffed with this one as to what could be causing the problem so any advice appreciated.

[shack]

Good day. Air con started playing up a few years ago wouldn't come on for about 5 minutes gradually got worse and now it works only when it wants to. When its working its great but I would prefer that I control it rather then it decides when to work. Had it looked at and gas was full was told its the compressor but cant be that as it works fine when its decides to work.
Just changed the pollen filter because when I opened the window the air con started to work so thought the change in internal air pressure was causing it (wishful thinking, of course no improvement) so thought maybe temperature sensor. I also saw a land rover notice some valve on the compressor cause an intermittent problem .
What do you guys think , should I go with changing the compressor or maybe find someone who will diagnose the valve which is $50 and I think is accessible from the LHS tyre well or is there something else I can check and replace.
I like to do stuff myself and changed timing belt and manifolds but am a bit stuffed with this one as to what could be causing the problem so any advice appreciated.

It'll be the RCV.

Just about always is.

[John_D4]

It'll be the RCV.

Just about always is.

Sorry, but I really don’t know - what’s an RCV?

[shack]

Sorry, but I really don’t know - what’s an RCV?Refrigerant Control Valve.

Essentially a proportioning valve for clutchless compressors.

[DiscoJeffster]

Refrigerant Control Valve.

Essentially a proportioning valve for clutchless compressors.

So as it happens, it’s on clutched compressors too, as per LR.

[terry1738]

It'll be the RCV.

Just about always is.
From what I have read you remove the electrical connector, remove the circlip, try to pull it out in one piece, put the new one in and insert the circlip and plug in the connector. I don't know how it works but i assume those holes in the bottom of the RCV twist around to limit the flow of gas through the compressor if so when I remove the valve i am going to lose my gas so i guess you need to close off the gas somehow, if that is right? and if so how do i close off the gas or don't I need to.
I have also read you can do this through the wheel well if you can get the car off the ground and have skinny arms and the patience of Zeus non of which I possess otherwise there is a lot of removal replacement to get down to the compressor.
Is it even remotely possible to do it through the wheel well?
Thanks for the reply and confirming my thoughts that it was the RCV. Terry

[shack]

So as it happens, it’s on clutched compressors too, as per LR.As far as I'm aware the compressors on all D3 and D4 variants are clutchless.

They use an RCV to control output/ compressor output - variable displacement.

Where the confusion possibly arises is they they also all have a "safety clutch".

This doesn't operate like the old school clutched compressors though.

I believe once the safety clutch has been brought into play.. It's cooked.

I think on sanden units the "clutch" is non replaceable.

But I stand to be corrected.

[DiscoJeffster]

From what I have read you remove the electrical connector, remove the circlip, try to pull it out in one piece, put the new one in and insert the circlip and plug in the connector. I don't know how it works but i assume those holes in the bottom of the RCV twist around to limit the flow of gas through the compressor if so when I remove the valve i am going to lose my gas so i guess you need to close off the gas somehow, if that is right? and if so how do i close off the gas or don't I need to.
I have also read you can do this through the wheel well if you can get the car off the ground and have skinny arms and the patience of Zeus non of which I possess otherwise there is a lot of removal replacement to get down to the compressor.
Is it even remotely possible to do it through the wheel well?
Thanks for the reply and confirming my thoughts that it was the RCV. Terry

It is under gas pressure so you will lose the gas so legally you need to get the gas recovered by a certified AC technician. The system will then need to be pressurised with nitrogen preferably which will help you to get the valve out. You will then change the valve and need to get the system regassed. After that you might see improvement, or not, depending on the health of the compressor.

[BradC]

As far as I'm aware the compressors on all D3 and D4 variants are clutchless.

....

But I stand to be corrected.

That's a hill I was prepared to die on, but the compressor on the 3L has a clutch in addition to being variable. The 2.7L does not have an electromagnetic clutch.

[shack]

That's a hill I was prepared to die on, but the compressor on the 3L has a clutch in addition to being variable. The 2.7L does not have an electromagnetic clutch.Thanks for that..

I knew I wouldn't be standing alone!

Under what circumstances does the clutch operate on a 3 litre?

[BradC]

Under what circumstances does the clutch operate on a 3 litre?

Don't know. It's not discussed in the workshop manual I have, but it is on the wiring diagram.

Edit : I wonder if it's related to lubrication. On the 2.7 when the AC is off the compressor still runs at minimum displacement. That's going to very slowly carry oil out of the compressor and I'd wager some sits in both the condenser and evaporator. That'll return to the comp when the refrigerant flow increases, but perhaps when it's off for extended periods (like the Econ button is pressed) then there could be a time when the compressor has insufficient oil.

Being able to switch the compressor off completely would then prevent that from happening.

[DiscoJeffster]

3L only turns off the compressor when you press the AC button on the dashboard. The rest of the time it’s engaged.

[scarry]

The 2.7L does not have an electromagnetic clutch.

So what happens on a High or low pressure fault,if the compressor cannot be electrically stopped?

FWIW,as for oil return at low load,in non Auto air systems,smart systems will time the period of low load operation,then load up for a short timed period,then back to low load and repeat.

[DiscoJeffster]

So what happens on a High or low pressure fault,if the compressor cannot be electrically stopped?



You tell me? Fact is it doesn’t have one. As for the consequences of that in a fault scenario [emoji2373][emoji2373][emoji2373]

[scarry]

You tell me? Fact is it doesn’t have one. As for the consequences of that in a fault scenario [emoji2373][emoji2373][emoji2373]

Maybe for High pressure it has an internal relief valve,back into the suction side of the compressor?

Whether it has one or not the compressor will keep running and eventually fail,but having an internal relief valve will reduce the danger of high pressure refrigerant being released.

Seems a badly engineered system to me,but what would I know[bigrolf]

[Graeme]

My 4.4 TDV8's compressor also has a clutch. It's engaged at idle even though the a/c is switched off but presumably disengaged in some circumstances, possibly on low and or high gas pressure to protect the system.

[BradC]

So what happens on a High or low pressure fault,if the compressor cannot be electrically stopped?

On low pressure it'll just grind the compressor to dust. Under high pressure something will break or burst. In either case there's a sacrificial coupling in the compressor pulley that snaps to ensure a lunched compressor doesn't take out the other accessories on the belt.


FWIW,as for oil return at low load,in non Auto air systems,smart systems will time the period of low load operation,then load up for a short timed period,then back to low load and repeat.

Yeah, If I'm near the condenser when it happens the oil return cycle on our Panasonic sounds like a turbine spooling up.

[scarry]

On low pressure it'll just grind the compressor to dust. Under high pressure something will break or burst. In either case there's a sacrificial coupling in the compressor pulley that snaps to ensure a lunched compressor doesn't take out the other accessories on the belt.

What a wonderfull set up[bigrolf]

[DiscoJeffster]

I knew I shouldn’t have commented on this post. Yesterday my AC decided to do the failing valve trick by constantly cycling off and going warm. Turning off the AC (D4 3L) for a minute gets it going again, for a little while. Yesterday it was only working for minutes at a time.
Having just dropped $3.5k to fix the stupid EGR leaking into the cooling system and leaking oil cooler, I really don’t feel like spending more on this thing right now. Grumble grumble.

[stuarth44]

It is under gas pressure so you will lose the gas so legally you need to get the gas recovered by a certified AC technician. The system will then need to be pressurised with nitrogen preferably which will help you to get the valve out. You will then change the valve and need to get the system regassed. After that you might see improvement, or not, depending on the health of the compressor.
I got a comp from UK 830 inc freight

[Graeme]

Yesterday my AC decided to do the failing valve trick by constantly cycling off and going warm. My understanding of the sticky valve fault is that the a/c is slow to start but keeps going thereafter. If this the case then maybe your system is just low on gas.

[DiscoJeffster]

My understanding of the sticky valve fault is that the a/c is slow to start but keeps going thereafter. If this the case then maybe your system is just low on gas.

Possibly. I was about to say it was only a couple of years ago I had the valve changed and regas, and then I checked the records 11/2019, so that’s four years ago!

Great idea, regas it is.

[shack]

My understanding of the sticky valve fault is that the a/c is slow to start but keeps going thereafter. If this the case then maybe your system is just low on gas.I'm pretty sure the fault with ours was the RCV, but the end result was really random performance, it would come and go off at will. Sometimes a bumpy road helped.

[shack]

What a wonderfull set up[bigrolf]Yep, crap indeed.

The only thing I may add to possible safety features is that there is a pressure switch/sensor, and the operation of the RCV in this scenario.

One possible way to diagnose RCV vs gas level is that when the AC is turned on, the ECM will add extra fuel to it's inject routines to compensate for the extra load created by the compressor.

If the gas is low, this doesn't seem to happen, if the gas level is ok and the RCV has failed to the "destroke" position, the engine idle speed will increase as the compensation fuel is still added, with the expectation that the RCV "commanded position" has been attained, and therefore we have extra load.

If the gas is low but the system has integrity, I'm guessing the the RCV would be commanded to minimum, which should hopefully save the compressor.

If the system is breached, you get the grey death..... And a repair bill that's more than the value of the car.

As always, I await my orders to ascend to the top of Mt. correction.....

Cheers

[BradC]

If the gas is low, this doesn't seem to happen, if the gas level is ok and the RCV has failed to the "destroke" position, the engine idle speed will increase as the compensation fuel is still added, with the expectation that the RCV "commanded position" has been attained, and therefore we have extra load.

It's not a case of "add extra fuel resulting in a higher idle". The HVAC ECU monitors the evap temperature. If the temperature isn't dropping fast enough (or at all) it asks the ECM to idle up a notch. This then happens a second time. So if it's low on gas and not cooling then you'll wind up idling at 1000RPM as it tries to add extra cooling.

Same effect as you indicate but the mechanism isn't different. It's not adding fuel to cope with the load of the compressor, it's giving the ECU a higher target RPM.

[shack]

It's not a case of "add extra fuel resulting in a higher idle". The HVAC ECU monitors the evap temperature. If the temperature isn't dropping fast enough (or at all) it asks the ECM to idle up a notch. This then happens a second time. So if it's low on gas and not cooling then you'll wind up idling at 1000RPM as it tries to add extra cooling.

Same effect as you indicate but the mechanism isn't different. It's not adding fuel to cope with the load of the compressor, it's giving the ECU a higher target RPM.Thanks, I'll walk up the mountain a little way...

[shack]

All things considered, I think I'll stop commenting on D3 D4 AC issues.

Obviously above my pay grade!

[TonyC]

All things considered, I think I'll stop commenting on D3 D4 AC issues.

Obviously above my pay grade!

Don't stop, everyone's input is very enlightening (or terrifying) for a 300Tdi Defender owner 🥺

Tony

[LuckyLes]

All things considered, I think I'll stop commenting on D3 D4 AC issues.

Obviously above my pay grade!
I don't think it's above your paygrade, some others maybe.

[RANDLOVER]

..............

If the gas is low but the system has integrity, I'm guessing the the RCV would be commanded to minimum, which should hopefully save the compressor.

If the system is breached, you get the grey death..... And a repair bill that's more than the value of the car.

As always, I await my orders to ascend to the top of Mt. correction.....

Cheers

I think the grey death is also caused by low gas which then can't carry the oil around the system, which results in extra wear and thus grey particulate matter known as "the grey death".

[BradC]

Thanks, I'll walk up the mountain a little way...

Apologies, it wasn't meant like that. One of those mornings I'm afraid.

[shack]

Apologies, it wasn't meant like that. One of those mornings I'm afraid.No no! I didn't mean it in any kind of "I'm grabbing my ball and going home" way, all good..

And yes, I was also having one of those mornings... Weeks.. And possibly months.

[PerthDisco]

Is there a patron saint of car AC I need to hang from the rear view mirror and praise daily?

[RANDLOVER]

Is there a patron saint of car AC I need to hang from the rear view mirror and praise daily?

St Christopher is supposedly the patron saint of travellers, and I assume you'd be travelling with the a/c on, not sitting around.

[BradC]

Is there a patron saint of car AC I need to hang from the rear view mirror and praise daily?

Not as such, but consider a routine re-gas every couple of years. By the time you notice the cooling is impaired you've also impacted oil circulation and are likely to affect compressor life.

If your workshop is any good they'll weigh the gas out and weigh the correct charge back in. That'll be a decent indicator of how fast its leaking (no, I don't want to hear that new compressor seals don't leak. Everything leaks, even brazed hermetics. It's the leak rate that counts).

[scarry]

Not as such, but consider a routine re-gas every couple of years. By the time you notice the cooling is impaired you've also impacted oil circulation and are likely to affect compressor life.

If your workshop is any good they'll weigh the gas out and weigh the correct charge back in. That'll be a decent indicator of how fast its leaking (no, I don't want to hear that new compressor seals don't leak. Everything leaks, even brazed hermetics. It's the leak rate that counts).

Due to much better manufacturing techniques and better products,engineering,and design,many auto air systems can go 15 to 20yrs without repairs or adding gas to the system.This was unheard of 30 yrs ago.

FWIW,the complete opposite has happened in commercial refrigeration,over the years,and now with the very poor quality copper in paired tubing,the same is unfortunately happening in the smaller AC industry.
And here we are trying to save the world.[bigsad]