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Air Conditioner not getting cold after body off re-gas
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dreynolds10
 


Member Since: 11 Jun 2013
Location: Berks
Posts: 166

United Kingdom 2006 Discovery 3 TDV6 HSE Auto Java BlackDiscovery 3

When the second regas was done I did check the gauges on the machine. Given the engine is required to run when pulling in the new refrigirent when this was complete and before disconnecting the lines the readings were

low pressure just under 4bar
High pressure circa 5 bar.

When revved the high pressure increased slightly but not much change in the low pressure.

Given the numbers are similar do you think this points to compressor failure?

Cheers
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Post #180796525th Apr 2017 9:33 pm
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JMack
 


Member Since: 02 Aug 2014
Location: Edinburgh
Posts: 1517

Scotland 2006 Discovery 3 TDV6 Commercial Manual Java BlackDiscovery 3

Compressor wasn't running by those pressures.

I'd expect more like, 2 Bar and 10+ Bar or similar depending on temperatures and other factors.
  
Post #180796825th Apr 2017 9:41 pm
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segrub
 


Member Since: 12 Apr 2015
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United Kingdom 2008 Discovery 3 TDV6 HSE Auto Tonga GreenDiscovery 3

Afraid so way too high on low side.If the system was over charged discharge would have been even higher.Had wondered if they had pulled a vacuum and just pulled charge in.The low side side should be about half of that hard to give actual figure without knowing temperatures but that rules out blockage
  
Post #180796925th Apr 2017 9:42 pm
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segrub
 


Member Since: 12 Apr 2015
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United Kingdom 2008 Discovery 3 TDV6 HSE Auto Tonga GreenDiscovery 3

The fact that high pressure rises when revving makes me think comp is running but has failed.
  
Post #180797025th Apr 2017 9:44 pm
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dreynolds10
 


Member Since: 11 Jun 2013
Location: Berks
Posts: 166

United Kingdom 2006 Discovery 3 TDV6 HSE Auto Java BlackDiscovery 3

Pressure riaised slightly on the machine when reving but on IID (after the regas) it's pretty stable around 5bar when drivimg and then settles to about 4.5 on idle. I dont know whether IID is measuring high side or low side of the A/C though???

is compressor failure a common issue? Haven't seen it mentioned much on the forum so I'm thinking if it's not then it might be worth buying a second hand one rather than paying 400+ for a new one???
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Post #180797125th Apr 2017 9:44 pm
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lynalldiscovery
 


Member Since: 22 Dec 2009
Location: Maidstone
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United Kingdom 2006 Discovery 3 TDV6 Metropolis LE Auto Bonatti GreyDiscovery 3

Could it be something to do with the cooling fan not coming in when extra a/c cooling needed?
Im thinking if it wasnt an issue before body off but is now its something you have done/not done.

I think you will find the a/c is on all the time and the adjustable swash plate in the a/c pump adjusts how much work it does, so there is no pulley clutch like cars of old, when you push the off button all it does is tell the a/c pump to idle but its still turning just not pumping.

One of many sites https://macsworldwide.wordpress.com/2013/0...ompressor/
  
Post #180802126th Apr 2017 5:55 am
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lynalldiscovery
 


Member Since: 22 Dec 2009
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Forgot to add Im sure my a/c reads 6 bar with engine off and 4 bar ish with it running and cooling.
  
Post #180802226th Apr 2017 5:57 am
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dreynolds10
 


Member Since: 11 Jun 2013
Location: Berks
Posts: 166

United Kingdom 2006 Discovery 3 TDV6 HSE Auto Java BlackDiscovery 3

Hi Guys

Thanks for all the relies and ideas thus far. I continued my diagnostics today and have seen some strange behaviour which may give some indication of where the faults lies. I'd welcome your thoughts. Here is the behaviour....

I pulled the Pressure switch off and ran engine to see if this would kick start a fault. Indeed I got two, pressure switch fault plus system running outside of max pressure fault.

With the pressure switch disconnected, I ran the engine (on idle) and noticed the IID reading (something like) 3178kPa Shocked yes thats 3.1MPa

I believe the compressor has a relief valve built in for safety in case the pressure gets way high and this should kick in around 3.1MPa.

So I switched off PDQ before anything went bang. I then replaced the pressure switch and fired up the car.

IID now showed an immediate pressure of 16KPa and, this is the strange thing, the vents were blowing like an Arctic winter. Very chilly and certainly working as designed.

I went for a short drive (trying not to freeze in my newly acquired arctic conditions) and monitored the Pressure.

IID started at 16KPA but then reduced progressively to about 4KPA. As the pressure dropped, the heat in the vents rose. I soon lost the Arctic Blast and the vents reverted to mild spring air.

Given this behaviour was so bizarre, I repeated the test, with the same results.

I also noticed that by pulling the Pressure switch the IID seems to default to 31MPA straight away. It happens without the engine running and is immediate so I suspect that is a default reading rather than an actual pressure.

So if I pull the Pressure switch, start the engine, switch off, replace the switch I will get cold air for a short time whilst pressure reduces to about 4.5KPa

I can repeat the tests consistently with the same results.

Any thoughts?
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Post #180811426th Apr 2017 12:15 pm
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JMack
 


Member Since: 02 Aug 2014
Location: Edinburgh
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Scotland 2006 Discovery 3 TDV6 Commercial Manual Java BlackDiscovery 3

16kpa is about 2.5psi, so would barely register on a set of pressure gauges.

So by the sounds of that you are short of gas.
  
Post #180817926th Apr 2017 4:37 pm
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dreynolds10
 


Member Since: 11 Jun 2013
Location: Berks
Posts: 166

United Kingdom 2006 Discovery 3 TDV6 HSE Auto Java BlackDiscovery 3

Apologies for the confusion...Thats a typo...it was 1600KPa so good pressure and good cooling (for that short period of time until it declined as per the above txt).
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Post #180818326th Apr 2017 4:41 pm
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JMack
 


Member Since: 02 Aug 2014
Location: Edinburgh
Posts: 1517

Scotland 2006 Discovery 3 TDV6 Commercial Manual Java BlackDiscovery 3

Thought that might have been the case.

Can you take an IID tool reading of the; Pressure (Bar) Compressor current (Amps) Evaporator Temp (C) and Interior Temp (C).

And then we'll have some firm data to look at.


I've just checked mine and will post up some screenshots to compare.
Thumbs Up
  
Post #180821826th Apr 2017 5:50 pm
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dreynolds10
 


Member Since: 11 Jun 2013
Location: Berks
Posts: 166

United Kingdom 2006 Discovery 3 TDV6 HSE Auto Java BlackDiscovery 3

Hi JMack

Thanks for the offer to compare with yours. I'll take some screen shots and post to see if it helps but can't get to the car now until Friday but here is what I remember from my diagnostics today.

Obviously temps are dependent on time of day and the car engine heat.

Early morning the outside temp was 3C so not much help as the AC doesn't kick in below 5C (I believe) However the pressure was reading around 275KPa at that time (2.75bar). I ran the AC but obviously it was a useless test given the outside temp.

In the afternoon when the outside temp had risen to 9C this is when I discovered that pulling the high pressure switch would cause the AC to blow cold (after pulling then re plugging in as per the pattern mention in my post above)

Pressure went up to 1600KPA (16bar) but would then drop to 475kPa after a while (and the AC would become ambient temp).

I did notice that when I pulled the High pressure switch the Compressor current went from 130A to 0 which is what you would expect but when I plugged it back in Pressure would clime to 1300KP+ and current would go up to 210A

All of the above are from memory but I can try and repeat the cycles on Friday when I have more time and post some screen shots.

Also, I did put a multimeter across the pressure switch to confirm it was reading 5V.

So it seems that there is an intermittent fault that is closing/opening the AC circuit but not when it should.

I'm coming to the conclusion that its the Compressor but given how difficult it is to replace/change I am hoplessly trying to convince myself its something easier. Pressure switch could be the culprit also as its definitely switch related (switching circuit open/closed).

Questions is whether thats electrical (pressure switch or compressor switch) or mechanical (compressor)

Thanks again.

Ian
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Post #180824626th Apr 2017 6:39 pm
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JMack
 


Member Since: 02 Aug 2014
Location: Edinburgh
Posts: 1517

Scotland 2006 Discovery 3 TDV6 Commercial Manual Java BlackDiscovery 3

My screen shots:

Shortly after starting engine and turning temp fully down to blue.





After running for a couple of minutes.




After turning A/C off and heating up and then A/C back on to cool down again.





My lowest compressor Amps was 129A, highest was probably over 190A.
Lowest pressure was about 4.6 (when just started) highest was 14ish.
Evap temp lowest was 2.0, highest was aout 22 before turning A/C on.
Cabin temp started at 23 and was down to 16 in about 5 minutes.
Outside temp was 6deg C.
  
Post #180828726th Apr 2017 7:19 pm
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dreynolds10
 


Member Since: 11 Jun 2013
Location: Berks
Posts: 166

United Kingdom 2006 Discovery 3 TDV6 HSE Auto Java BlackDiscovery 3

Hi JMack

Thanks for posting. Very useful and consistent with my readings (from memory) today when I did manage to get the compressor to kick in.

I'm slowly resigning myself to forking out 400 notes on a new compressor and spending the bank holiday weekend fitting it Big Cry

I just hope that is indeed the cause of the problem. Question

Thanks again for taking the time and effort to provide your readings Thumbs Up
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Post #180829326th Apr 2017 7:24 pm
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JMack
 


Member Since: 02 Aug 2014
Location: Edinburgh
Posts: 1517

Scotland 2006 Discovery 3 TDV6 Commercial Manual Java BlackDiscovery 3

If your operating figures are similar then I'd hold off ordering that compressor.
It sounds more like yours is going off when it shouldn't for some reason that doesn't (initially) look to be a compressor fault.

Relay as previously mentioned, cabin temp sensor, Econ switch etc, etc.
  
Post #180830726th Apr 2017 7:37 pm
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