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MY 2012 XF S Portfolio Ultimate Black
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Discussion Starter #1 (Edited)
My car started to blow warm damp air only when the car is stationary and AC on. On the move it’s very cold. I was about to order the DPS other discussions suggest but decided to follow the diagnosis method mention in the document that John shared.
My problem is SDD shows the compressor is off. and as per workshop manual it should not be the DPS. Strangely the AC high pressure sensor reading jumps between 0 and 12kPa. (Effectively no pressure). Since car blows cold air on the move, I don’t think that is correct. I am going to test the pressure sensor wiring first. Maybe it’s loose and vibrations while travel make it working. But I have some questions and appreciate your input:
-Does anyone knows why the bulletin name the device DPS valve? Even the workshop uses “AC compressor solenoid valve” that matches the functionality. Does it have anything to do with pressure sensing? Like reading to causing the High pressure to become zero?!

-Also using the compressor model name, there are AC compressor valves listed for £15 and they look very identical to JLR part. Any one tried them?

-My last question is if my AC Pressure Sensor is gone, I need to replace it. I see on U tube it is a DIY job because it normally sits a valve with needle that will seal when you remove it. Does anyone know if XF is specifically like that or gas has to be removed first?

Thanks

p.s. if you follow my posts, you know that I would celebrate if I finish a week without any faults on the car 🤓
 

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Funnily enough I noticed that my aircon is not as effective when stationary for a reasonable length of time and wondered whether it was always that way or a growing problem!

My first thought was whether a fan had stopped working as it's fine as soon as there's some airflow over the car, i.e. you're in motion..

Watching this thread with great interest now Hamed.. (y)
 

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Watching with interest as well.

Mine also only blows cold when I'm moving and the car often mists up when I stop.

Sent from my SM-G975F using Tapatalk
 

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Just remembered that recently I downloaded from somewhere a Jaguar Training document on Climate Control Systems: 711-JAG: Jaguar Climate Control Systems

It might be of some use, all the info may already be in the workshop manual, haven't had a look yet...
 
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Has the cabin filter been changed? Misting up usually means it's bunged up.
 
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There isn't enough space to get the DPS valve out without removing the compressor.

I had the same symptoms for the past two years, only getting cold air at higher speeds (with the speed required to get cold air gradually getting higher and higher).

I'd exhausted my diagnostic abilities by last summer - and SDD had never shown any A/C related faults. I took the car to be looked at.
We discussed the possibility of the DPS needing replacement - however it was the compressor that was diagnosed as being faulty.
The replacement compressor solved the problem for a few months.
Over the winter just gone - the windows were steaming up when stationary, then in warmer weather I had warm air when stationary again

The HVAC module was replaced this time - and for the first time in a long time, my air conditioning is working as designed!

Sent from my VOG-L09 using Tapatalk
 
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I experienced most of the above in my XF. Indy diagnosed DPS (direct pressure sensing) valve. Replaced and cured.
If this doesn't work, the cooling fan never gets a signal to run. So at speed, the condenser is being cooled and the AC works. When stationary, no condenser cooling and the AC doesn't work.
Now, I can't say that this is the problem with the OP's car but from the description of the symptoms, it's a fair guess.
 

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Discussion Starter #8
Funnily enough I noticed that my aircon is not as effective when stationary for a reasonable length of time and wondered whether it was always that way or a growing problem!

My first thought was whether a fan had stopped working as it's fine as soon as there's some airflow over the car, i.e. you're in motion..

Watching this thread with great interest now Hamed.. (y)
Just remembered that recently I downloaded from somewhere a Jaguar Training document on Climate Control Systems: 711-JAG: Jaguar Climate Control Systems

It might be of some use, all the info may already be in the workshop manual, haven't had a look yet...
This document is very interesting Pete. Many Thanks.
Mine is like sometimes it is less effective and sometimes it blows damp warm air that mists windows badly that screen demister cannot cope with that.
 

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Discussion Starter #9
Watching with interest as well.

Mine also only blows cold when I'm moving and the car often mists up when I stop.

Sent from my SM-G975F using Tapatalk
We’ll at least go through a procedure to find the problem.
 

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Discussion Starter #10
Has the cabin filter been changed? Misting up usually means it's bunged up.
Mine hasn’t change and I get your point but I doubt that’s the case. The windshield will mist immediately when stop and clears when moving off.
 

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Discussion Starter #11
There isn't enough space to get the DPS valve out without removing the compressor.

I had the same symptoms for the past two years, only getting cold air at higher speeds (with the speed required to get cold air gradually getting higher and higher).

I'd exhausted my diagnostic abilities by last summer - and SDD had never shown any A/C related faults. I took the car to be looked at.
We discussed the possibility of the DPS needing replacement - however it was the compressor that was diagnosed as being faulty.
The replacement compressor solved the problem for a few months.
Over the winter just gone - the windows were steaming up when stationary, then in warmer weather I had warm air when stationary again

The HVAC module was replaced this time - and for the first time in a long time, my air conditioning is working as designed!

Sent from my VOG-L09 using Tapatalk
I agree HVAC module could cause this. Mine doesn’t show any error but when I use the data logger, I see compressor switches off while stationary. Because the pressure reads zero! Older cars used to switch the compressor one and off (it’s clutch). That’s not the case on XF. The compressor clutch is almost always engaged unless switched off from menu or HVAC module suspects a situation that can damage the system like very high or low pressure. Instead the system used AC compressor control valve aka DPS valve to change the flow so it can keep the compressor running at minimum load instead of switching it off.

so problem would be either the pressure sensor reading wrong value, HVAC sending wrong ref voltage to sensor, seleniod valve stuck, bad compressor or low gas.

because mine is really cold on the move, I would say gas is fine.Ref voltage is 4.95v from SDD. So if I can read it using multimeter the pressure sensor should be bad. DPS valve is my last bet because if it’s bad the AC shouldn’t be as cold as it used to on the move as well.
 

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Discussion Starter #12
I experienced most of the above in my XF. Indy diagnosed DPS (direct pressure sensing) valve. Replaced and cured.
If this doesn't work, the cooling fan never gets a signal to run. So at speed, the condenser is being cooled and the AC works. When stationary, no condenser cooling and the AC doesn't work.
Now, I can't say that this is the problem with the OP's car but from the description of the symptoms, it's a fair guess.
Compressor control valve (dps) is my last chance mainly because it is hardest to reach and needs emptying the gas. Plus following the advice on the bulletin that you shared DPS valve is not a problem. In that document it assumes the compressor is running but mine reads zero with SDD. If it runs and AC doesn’t work then It’s most likely low refrigerant flow caused by DPS valve.
I can read evaporator temperature which is 25-27 ‘c using SDD and it was like 13 ‘c outside. This confirms it’s indeed blowing warm air as I feel.
My guess is car tries to extract the humidity by warming evaporator to melt the frost but there is no cooling function.
Was your AC ice cold when moving and only had problem while stationary?
 

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The cabin filter is supposed to be changed every second service and often overlooked. Worth checking before delving into something more expensive.
 
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Discussion Starter #14
The cabin filter is supposed to be changed every second service and often overlooked. Worth checking before delving into something more expensive.
Sure will do
 

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. . . .
Was your AC ice cold when moving and only had problem while stationary?
Really don't remember. Just that I needed to be driving at speed for it to be blowing cold.
Yes, the compressor is driven by an electric clutch and if you'd said the ac wasn't working at all, I'd be advising checking the relay that powers it. But if you're getting cold (colder than outside air) when moving then I'd suggest the compressor is running.
The DPS fail is a common fault and if I were you, that's where I'd be looking to get replaced. I think I paid my indy just over £200 to do it.
 
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Discussion Starter #16
Really don't remember. Just that I needed to be driving at speed for it to be blowing cold.
Yes, the compressor is driven by an electric clutch and if you'd said the ac wasn't working at all, I'd be advising checking the relay that powers it. But if you're getting cold (colder than outside air) when moving then I'd suggest the compressor is running.
The DPS fail is a common fault and if I were you, that's where I'd be looking to get replaced. I think I paid my indy just over £200 to do it.
Thanks John. I tested the pressure sensors and it was reading fine. The connected my gauge to high pressure port and it was almost empty. Poor pressure sensor was correct. I am waiting for a UV light to find the leak. So it seems low gas level has a similar symptom. 🙄 I think it was on the margin so ambient temperature was affecting it making compressor to kick in and out. I might take this opportunity to change the DPS valve just in case.
 

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Interesting Hamed, I must admit I've been wondering, bearing in mind the cars mileage (currently 113K miles), whether a re-gas would be a good idea 'just because'.. I think you've answered that question thank you. (y)

P.S. when distances are measured in miles we call it mileage.. what do places that use KM's call it?... ❔
 

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'K' probably?
 

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Clickage?
 
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