Member Since: 04 Feb 2015
Location: Essex
Posts: 13
Air conditioning / climate control
Right here goes..... After having my 2005 disco air con recharged everything seemed fine , cold as the Arctic , just how I like it . After 2 weeks the air was not as cold as before so a quick call to the boys who did it , took it back in , on machine for 10 mins and everything seemed good as before . So after about 3 weeks of working fine , the same has happened again . I have checked relevant fuses , and all seems fine . But ...... The compressor is not kicking in . It was pressure tested and all seemed fine , but if there was a slow leak somewhere , would this prevent the compressor from
Kicking in . There is some pressure in the system as I have checked the valves on the pipes under the bonnet . Any advice would be much appreciated !!
13th Aug 2015 10:05 pm
Allan_T
Member Since: 10 Sep 2012
Location: Northampton
Posts: 1034
If I recall correctly the compressor is a permanently engaged variable displacement, clutchless design.GAP IID Pro Multi Vehicle Defender L316 2007-2015 - Discovery 3 - Discovery 4 - Discovery Sport L550 - Freelander 2 - Range Rover Evoque L538 - Range Rover L322 - Range Rover L405 - Range Rover Sport L320 - Range Rover Sport L494 Electrical Fault Diagnostics
13th Aug 2015 10:38 pm
lynalldiscovery
Member Since: 22 Dec 2009
Location: Maidstone
Posts: 7274
Tony what spec is the car?
If its has rear a/c its quite common for the pipes to corrode and pinhole, apparently the o rings can also dry out and let by.
Mine would pass the a/c vac test but 2 weeks later would go weak again, eventually traced it to the rear a/c pipe that runs along the inside of the passenger side sill.
I fixed mine but some people bypass them with an oe land rover pipe for about 60 quid.
14th Aug 2015 6:56 am
Tony251
Member Since: 04 Feb 2015
Location: Essex
Posts: 13
Tdv6 se, you say rear air con , in the back of the centre console the is 2 vents , I take it you mean this by rear air con ??
14th Aug 2015 7:10 am
tayaste
Member Since: 15 May 2013
Location: Chester
Posts: 7633
No, he means Rear Air Con, some come with a rear air con system as an option with with separate controls for the rear occupants fitted to the dome light
14th Aug 2015 7:45 am
maplecottage
Member Since: 01 Feb 2011
Location: Norfolk
Posts: 3171
IIR - Rear AC normally only found on HSE models.
Easy to see if you've got it - simply look behind the NS rear panel where the fuses are. If you have a nice big space, no AC - if you have a big fan thingy, rear AC
PS - silly question perhaps but you've not got the 'econ' button pushed in by chance
Even easier to look for the button at the front or dials on the roof though! Current: Discovery 3 06MY (55 reg) HSE Auto Zambezi Silver Allisport Fast Road Intercooler, V8 Brakes, Silicone IC Hoses, EGRs Blanked, Remapped, De-Cat pipe, FBHIC
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14th Aug 2015 9:04 am
Tony251
Member Since: 04 Feb 2015
Location: Essex
Posts: 13
Right , so no rear air con is fitted . I had to look to make sure , it's amazing what you don't see when you sit in the front all the time !! Would it be possible there is a tiny leak somewhere , that is so small it would pass the pressure test undetected ??
14th Aug 2015 5:33 pm
Bodsy Site Sponsor
Member Since: 06 Nov 2006
Location: In the Clubhouse
Posts: 21361
they should have put some UV detectable dye in it last time they filled it. Use a blacklight to have a look around the pipework and the joins and the radiator etc.Bodsys Brake Bible
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14th Aug 2015 5:36 pm
lynalldiscovery
Member Since: 22 Dec 2009
Location: Maidstone
Posts: 7274
I found my leak by pressurising it with nitrogen and going around all the joints with soapy water.
Condenser rad is another air con failure favourite, done a couple on cars but not a D3, rads not that dear either.
If its a real slow leak the a/c machine will think all is okay and refill the system.
14th Aug 2015 6:12 pm
dlw
Member Since: 03 Dec 2014
Location: Wellingborough
Posts: 374
I have the same issue, I replaced the condenser and had it charged and I still have nothing. I tried to have it charged up a while ago but it was leaking but at that time I got ice cold air until the gas ran out.
I have also noticed my wing mirrors are hot as if its in frost mode.
14th Aug 2015 7:02 pm
Tony251
Member Since: 04 Feb 2015
Location: Essex
Posts: 13
How long did the cold air last?? Mine lasted about 2 to 3 weeks before it was more hot than cold !!
14th Aug 2015 9:09 pm
dlw
Member Since: 03 Dec 2014
Location: Wellingborough
Posts: 374
About an hour
It took me more than a month to get around to changing the condenser
14th Aug 2015 10:11 pm
JMack
Member Since: 02 Aug 2014
Location: Edinburgh
Posts: 1517
There is a (low) pressure switch that will stop the compressor from running if the system loses enough refrigerant.
A very small leak might be missed by a low pressure sort time pressure test or a brief vacuum test. So it is possible that there is a small leak somewhere that has leaked enough to drop the pressure below the cut-out for the pressure switch, but still have pressure in the system when yo manually check at the valve.
Check the compressor fuse is ok, then get someone competent to check the gas if the fuse is ok.
16th Aug 2015 12:17 am
Allan_T
Member Since: 10 Sep 2012
Location: Northampton
Posts: 1034
A/C Compressor Control
The variable displacement A/C compressor is permanently driven by the engine. The flow of refrigerant through the A/C compressor, and the resultant system pressure and evaporator operating temperature, is regulated by the refrigerant solenoid valve. Operation of the refrigerant solenoid valve is controlled by the ATCM using a 400 Hz PWM signal. The duty cycle of the PWM signal is calculated using the following parameters:
• A/C compressor torque
• A/C compressor torque maximum
• A/C cooling status
• A/C demand
• A/C refrigerant pressure
• Ambient air temperature
• Blower speed
• Engine cranking status
• Evaporator temperature
• Transmission gear status.
When A/C is selected, the ATCM maintains the evaporator at an operating temperature that varies with the in-vehicle cooling requirement. The ATCM increases the evaporator operating temperature, by reducing the refrigerant flow, as the requirement for air cooling decreases, and vice versa. During an increase of evaporator operating temperature, to avoid compromising the dehumidification function, the ATCM controls the rate of temperature increase, which keeps the cabin humidity at a comfortable level.
When the economy mode is selected, the PWM signal holds the refrigerant solenoid valve in the minimum flow position, effectively switching off the A/C function.
The ATCM incorporates limits for the operating pressure of the refrigerant system. When the system approaches the high pressure limit, the duty cycle of the PWM signal is progressively reduced until the system pressure decreases. When the system pressure falls below the low pressure limit, the duty cycle of the PWM signal is held at its lowest setting, so that the A/C compressor is maintained at the minimum stroke, to avoid depletion of lubricant from the A/C compressor. The protection algorithm is calculated at a high rate, to enable early detection of the rapid pressure changes possible if a system fault develops.
The refrigerant pressure sensor provides the ATCM with a pressure input from the high pressure side of the refrigerant system. The sensor is located in the refrigerant line between the condenser and the thermostatic expansion valve.
The ATCM supplies a 5V reference voltage to the refrigerant pressure sensor and receives a return signal voltage, between 0 and 5V, related to system pressure.
The ATCM uses the signal from the refrigerant pressure sensor to protect the refrigerant system from extremes of pressure and to calculate A/C compressor load on the engine. The ATCM also transmits the A/C compressor load value to the ECM, via the medium speed CAN bus, instrument cluster and high speed CAN bus, for use in controlling the speed of the engine cooling fan.
To protect the system from extremes of pressure, the ATCM sets the A/C compressor to the minimum flow position if the pressure:
• Decreases to 1.9 – 0.2 bar (27.5 – 3 lbf/in2): the A TCM loads the A/C compressor again when the pressure increases to 2.8 – 0.2 bar (40.5 – 3 lbf/in2).
• Increases to 33 – 1 bar (479 – 14.5 lbf/in2): the ATCM loads the A/C compressor again when the pressure decreases to 23.5 – 1 bar (341 – 14.5 lbf/in2).GAP IID Pro Multi Vehicle Defender L316 2007-2015 - Discovery 3 - Discovery 4 - Discovery Sport L550 - Freelander 2 - Range Rover Evoque L538 - Range Rover L322 - Range Rover L405 - Range Rover Sport L320 - Range Rover Sport L494 Electrical Fault Diagnostics
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Allisport Fast Road Intercooler, V8 Brakes, Silicone IC Hoses, EGRs Blanked, Remapped, De-Cat pipe, FBHIC
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