My 2006 2.7 TDV6 HSE has been having a lot of strange issues in the last three weeks. Temperature in my country is presently above 29C around this time of the year, so air conditioning is more or less mandatory for me.

Firstly, I had cool air coming from all the left vents and and warm (not-heated) air from the right vents. I took the car to a mechanic who simply recharged it, explaining that the refrigerant pressure was low. All the vents started cooling at that point, but then more serious issues started.

30 minutes later, the compressor cuts off and does not cool anymore, just warm air blowing from all vents. The following day it starts cooling again and works for an hour and stops. And that has been the case since then, sometimes it cools, sometimes it doesn't. Whenever it cools, it works perfectly until it cuts off. Pressing the OFF button over and over sometimes makes it start working again as this turns the system off and on.

I have asked around, and the general consensus is that the clutchless compressor needs to be replaced. I am a bit skeptical because I know the compressor cools very well whenever the system works. Asides, replacing the compressor is expensive and a whole lot of stress as it's practically located at the bottom of the engine.

Has anyone experienced anything like this? What are the possible causes and solutions?

If the system is charged correctly and has no leaks then I would imagine the compressor would be the next item to look at 2010 RRS, TDV8
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If the drier hasn't been changed in a long time or ever, then it may not be able to remove moisture from the system. If there is moisture in the air con system, water droplets will collect and freeze at the venturi of the evaporator on the high pressure inlet. As the water droplets freeze they block up the port and stop the circulation of refrigerant. The system then warms up as a result and the ice around the Evaporator venturi port melt, thus allowing the system to work as it should until the freezing up happens again. It will continue to cycle like this until the system is repaired. My advice is to go to a specialist aircon place, who should replave the drier and then vacuum the system down for a good hour to 'boil off' any moisture.
The symptoms you are having point me straight to moisture in the system. Having the drier renewed and the system regassed is obviously a lot cheaper than renewing the compressor. Hope you get it sorted

So I got the compressor replaced. It was a hell of a job for the workshop that fixed it. They had to remove all the turbo pipes and hoses, and still had a hard time getting the old compressor out. To top it all, a clutch type compressor was installed to replace the clutchless type. They advised that the clutchless type is more prone to failure and considering the effort and time required to install it, it's not just worth the risk installing another clutchless. The conversion worked well, the installed compressor (which works perfectly) now has a relay which controls it.

However.....

The clutch type compressor comes with fewer ribs on the pulley compared to all the other devices on the pulley system. The belt was changed to a smaller one also with fewer ribs. So far i have not had any issues with the a.c.

Personally, that's not an arrangement that I would be at all happy with. AFAIK, the swashplate design is not hugely unreliable at all, and is an excellent way of increasing efficiency. Most importantly, the system is integrated into the ECU systems so feedback from a binary clutch controlled compressor vs a variable swashplate isn't always going to match the vehicle's expectations.

Quote:

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 Pulse Width Modulated (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.

A/C Compressor Torque

The ATCM uses refrigerant pressure, evaporator temperature and engine speed to calculate the torque being used to drive the A/C compressor. The calculated value is broadcast on the medium speed CAN bus for the Engine Control Module (ECM), which uses the calculated value for idle speed control and fueling control. The ATCM also compares the calculated value with a maximum A/C compressor torque value received from the ECM over the medium speed CAN bus. If the calculated value exceeds the maximum value, the ATCM signals the refrigerant solenoid valve to reduce the refrigerant flow, to reduce the torque being used to drive the A/C compressor. By reducing the maximum A/C compressor torque value, the ECM is able to reduce the load on the engine when it needs to maintain vehicle performance or cooling system integrity.

A narrower belt is also something I certainly wouldn't entertain... Visiting from DISCO3.CO.UK
2006 Discovery 3 TDV6 Auto HSE Zambezi Silver

These were the same arguments I had concerning the compressor replacement. I am well aware of the benefits of the swashplate design and its complexities of course, but considering my location, spare parts prices and some other little factors, i had to agree to a conversion. In fact I did a lot of fact finding on availability of replacement parts, I got quotes from 4 different shops and sampled opinions on similar replacements.

I was quite surprised to find out that most mechanics (in Nigeria) simply replace the system with a clutch compressor. The reason they claim it's because they have a high failure rates on replacement clutchless system, beats me why.

One shop offered to replace with the proper oem compressor, condenser and drier but the cost was insane.

I eventually agreed to go with the clutch system after I visited a shop where i was shown a graveyard of replaced clutchless compressors.

As for the narrower belt, we had no choice. We couldn't find an 8-rib pulley compressor for diesel engines, so a petrol 6 rib pulley compressor was used.

If I'm correct, the Refrigerant Solenoid Valve is still in use in my setup, its been modified to directly drive the relay which engages the compressor clutch.