Few issues with AC on VEs.
Firstly, and this is more of a characteristic than an issue.
In extreme cases such as extended idling or very high ambient temperatures, some customers may complain of poor
air conditioner performance (“loses cooling”) after driving for some time whilst in “recirculation” mode. They may even
perceive that the air conditioner has “shut off”.
On hot days, the AC is much more effective when in recirc mode. In order to prevent the build up of excessive CO2
(Carbon Dioxide) in the cabin when in recric mode, the AC system will “purge” the cabin air after driving for a set
period of time. It does this by opening the recirc door 30% to let in some fresh air.
It should be noted that when the system is in recirc, no outside air is permitted to enter through the plenum system.
Therefore the occupants of the cabin continually breathe the re-circulated air at increasing levels of CO2 saturation.
Prolonged exposure to high concentrations of CO2 can cause multiple symptoms including lack of attention to detail
and fatigue.
When the purge occurs, a difference may be felt in the cooling effect of the AC. In some cases the customers may
think the AC has turned off.
Although the vent temperature only increases by a few degrees, the humidity can increase (depending on ambient
conditions) when this feature is initiated due to a sudden inrush of moisture laden air. The humidity is quickly returned
to normal levels but the initial change can make the customer think the AC has turned off.
The purge mode lasts for 10 minutes then the system returns to full recirc mode. During this time, the recirc telltale/
icon is still displayed on the switch/display.
The driving time before this feature is initiated varies depending on the HVAC module version installed in the vehicle
and the ambient temperature
Secondly,
The evaporator may ice up reducing or preventing air
flow through the HVAC system. If the vehicle is left
parked after an ice up event, excessive water may be
noticed under the vehicle. The A/C system
performance will improve after the vehicle is parked
for sufficient time for the evaporator to defrost. This
issue may be more common in high humidity
conditions.
CAUSES
1. Vehicles built between 27/11/08 and 29/04/09
Due to a sealing issue between the evaporator and the
case, the evaporator temperature sensor can be
affected by a small amount of un-cooled air. This
results in a false high evaporator temperature reading
causing the evaporator to “Ice up” as the system
attempts to achieve the required temperature.
2. Vehicles built after 29/04/09
Variation in the evaporator temperature results in the
evaporator temp sensor giving an inaccurate reading.
Thirdly,
V8 only
Under full throttle acceleration, the ECM disables the
Air Conditioning (A/C) compressor. This is normal
operation, however in some circumstances the ECM
may fail to switch the A/C compressor back on when
normal driving resumes.
Turning the HVAC controls off or cycling the ignition
temporarily rectifies this concern.
Do not confuse this condition with a faulty A/C module
which would be evidenced by the condensor fan not
working
CAUSE
The ECM software does not reinitiate A/C compressor
operation.
Also could be an AC belt thrown off.
Theres also various other reasons such as leaks at the TX valves, near the LP charge port etc etc.
