Member Since: 11 Jun 2013
Location: Berks
Posts: 166
Air Conditioner not getting cold after body off re-gas
Hi Guys
This one is having me chasing my tail somewhat so thought I'd ask the (expert) audience.
The issue is that my aircon is not getting cold after just having it re-gassed. I have searched the forums in detail and realise there are plenty of potential causes for this but please read below for full background and history.
Background
I have had the body off the D3 and rebuilt most of the car from the ground up so during this process it has had new flexible pipes connected from front to back (as it has the rear aircon) instead of the several aluminium parts which corrode/leak (in awkward to get to places). So I can now check and confirm that there are no leaks as I only have 3 points of connection which are all easily accessible.
Car has also had a new condenser during rebuild.
I have pressure in the systems at 500+ kPa (see below IID read out) after a drive which settles to circa 475 kPa at idle. This pressure is consistent over several days monitoring so another indication that there is no leak.
IID is showing no faults.
I have had the car regassed the twice to ensure that there were no blockages or mistakes in the amount of fluid inserted (810g +/- 25g for cars with rear aircon). The machine ran through the cycle fine and completed vacuum test successfully (again no leak).
Symptoms
The strange thing is that after the first regas the HVAC would run warm but on a long motorway trip all of a sudden the AC would kick in for about 10mins giving me lovely cold air and working as expected but it would then revert to just blowing normal air. This would repeat a couple of times over a 3 hour journey.
After the second regas, the car was initially slow to get cold but after running the engine above 2000rpm the front HVAC got cold from the Passenger side vents first, slowly creeping across to the drivers side. This lasted for about 2mins before again the cold disappeared and the blower went back to normal ambient air temp.
As a test I drove the car in Sport mode for about 3 miles keeping the revs above 2000rpm and the vents did start to get a "little colder", again starting from the passenger side but they never got up to the expected chill that you would expect. Back on idle it was back to ambient air.
If I lift the bonnet and hold the zircon pipes in the front (and the back) they don't feel that cold to the touch.
So I am at a bit of a loss. My last resort would be new compressor but that is a big expense if its not the problem.
I would appreciate any thoughts?
Thanks in advance
Disco3 project
25th Apr 2017 5:19 pm
JMack
Member Since: 02 Aug 2014
Location: Edinburgh
Posts: 1517
When it was re-gassed and checked, did it work okay then?
25th Apr 2017 5:38 pm
dreynolds10
Member Since: 11 Jun 2013
Location: Berks
Posts: 166
Hi JMack
Thanks for the reply. After the 2nd regas I tested whilst the car was still sitting next to the machine as soon as the H/L pipes were disconnected. Initially the air was NOT cold. I ran the engine up to above 2000rpm and held it there for about 2 mins and then the car did slowly get chilly starting with the passenger vent first then working its way across the dash to the drivers side.
As soon as I let the car return to idle the cold reverted to normal air blowing and has not come back
Pressure has remained constant.
Any ideas?Disco3 project
25th Apr 2017 5:45 pm
JMack
Member Since: 02 Aug 2014
Location: Edinburgh
Posts: 1517
If the pressure is remaining (reasonably) constant then the compressor isn't pumping.
I'm not sure of the wiring/controls for the compressor, but maybe there's a fuse that could be blown.
Or possibly a faulty pressure switch giving a false reading stopping the compressor from pumping.
Or having just typed that, and thought about your body off comments, then maybe the pressure witch hasn't been connected during the re-assembly.
25th Apr 2017 6:06 pm
dreynolds10
Member Since: 11 Jun 2013
Location: Berks
Posts: 166
Good ideas.
The pressure switch is connected. I checked that to make sure but no harm in re-checking (it could be faulty I suppose). Also, as the air did get cold sometimes then I would suspect the fuses are all working but again worth re-checking.
You have got me thinking though...one option could be faulty relay. A relay that is "on the way out" might give an intermittent fault as it was dying, switching on then off occasionally before it gave up the ghost completely.
I'll try an swap some relays around to test the theory and see if that makes a difference.
If you think of anything else then please keep the ideas coming
CheersDisco3 project
25th Apr 2017 6:11 pm
segrub
Member Since: 12 Apr 2015
Location: CAMBRIDGESHIRE
Posts: 32
Im afraid it does sound like the compressor.The only way to tell for sure is to install a set of guages.the other possible cause is a blockage or freezing up. With high and low side guages fitted you can determine problem without or you can do is electrical tests which you have already carried out.
25th Apr 2017 7:42 pm
dreynolds10
Member Since: 11 Jun 2013
Location: Berks
Posts: 166
Hi segrub
I am coming to the same conclusion ie compressor.
I've done some further diagnostics and don't think it's electrical. Last think to try is your suggestion to test compressor itself and confirm the inevitable.
Seems like a of a job to replace as well Disco3 project
25th Apr 2017 7:46 pm
woody32 Site Sponsor
Member Since: 11 Mar 2009
Location: Somerset
Posts: 3551
Did you have the engine out while the body was off Wanted D4s non runners pm for competitive price.
IID Pro MV License - D3/4 RRS - Enabling, Updates,Transmission flushing.
Mobile or workshop,PM for details.
25th Apr 2017 7:48 pm
dreynolds10
Member Since: 11 Jun 2013
Location: Berks
Posts: 166
Hi Woody
No engine stayed in....although nearly had the heads off for the glow plugs but that's a different story.
Didn't touch the compressor.
What you thinking?
I'm thinking that the drive to the garage to do the recharge may have led to a fubar'd compressor due to running without any oil in
Lesson learned if/when I replace and will do the recharge before moving but prior to that I will crank over the compressor few cycles to get the oil in or it could lead to another costly mistake.Disco3 project
25th Apr 2017 8:03 pm
woody32 Site Sponsor
Member Since: 11 Mar 2009
Location: Somerset
Posts: 3551
Was thinking along the lines of the plug at the compressor itself not plugged in fully but if you've not had it apart then that's out the window.
You won't of done any harm driving with no gas oil in the system you need to see if the clutch on the compressor is powering up easier said then done I know,you shouldn't need to rev the car to get it cold.
Just a thought Have you tried it on manual not auto poss internal temp sensor fault Wanted D4s non runners pm for competitive price.
IID Pro MV License - D3/4 RRS - Enabling, Updates,Transmission flushing.
Mobile or workshop,PM for details.
25th Apr 2017 8:52 pm
dreynolds10
Member Since: 11 Jun 2013
Location: Berks
Posts: 166
Hi Woody
Yes I tried it in manual also. Tried switching on/off and various other cycles of the HVAC in hope of trying to kick start it somehow. All failed.
I'll check the plug though as it might/could have got disturbed somehow - even if improbable its always worth checking.
Failing that I think I am looking down the barrel of a replacement compressor. Question is whether to go for new, recon or 2nd hand (from scrap).
If I do replace then I am thinking that going in from the Left hand side would be the lessor of two evils, compared to going in from front which would involve coolant and power steering fluid getting in the way?Disco3 project
25th Apr 2017 9:08 pm
segrub
Member Since: 12 Apr 2015
Location: CAMBRIDGESHIRE
Posts: 32
You wouldnt have damaged due to lack of oil as the oil is dragged around the system by the refrigerant.The system is protected by an low pressure switch for that reason. I e no pressure wont run comp.
The thing that is puzzling me is why th ey didnt pick this up when recharging system?
25th Apr 2017 9:10 pm
dreynolds10
Member Since: 11 Jun 2013
Location: Berks
Posts: 166
Hi segrub
The strange think is that straight after the regas and by running the engine at 2000rpm for a minute or two we had cold air at all vents. The. I leave, drive down the road and it's now down to normal ambient air blowing through the vent.
The additional weird thing is that on a long drive it tends to suddenly kick in and function correctly for a short period before then reverting to fail mode.
Much head scratching going on.
I would like to rule out the compressor but it might be an expensive and very work intensive mistake if I replace only to find out I still have the same problem.Disco3 project
25th Apr 2017 9:30 pm
JMack
Member Since: 02 Aug 2014
Location: Edinburgh
Posts: 1517
You need to get pressure gauges on it to check the pressures with engine running and revving etc.
Have you tried a HVAC re-set? Might be worth a try.
I'm sure there's a how-to either in the Wiki or in a post somewhere on the forum.
25th Apr 2017 9:58 pm
segrub
Member Since: 12 Apr 2015
Location: CAMBRIDGESHIRE
Posts: 32
This is why you need to get guages fitted to help diagnose, If the low pressure and high pressure guages read roughly the same when system should be running either clutch not engaging(not likely as it works at higher revs) or comp is shot.However if the the low side is pulling into a vacuum would indicate a blockage or faulty expansion valve(fits on end of coil under dashboard). Its very possible that you have a blockage as all pipes have been of so you want to eliminate this before expense of comp.you really do need to get some guages on to diagnose.The fact that it partialy works at high revs could well indicate a restriction.Dont think expansion vale is freezing up because of moisture in system as that normally starts out ok then stops working.
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of a job to replace as well 
