Thread: AirConditioning

Am relatively new to Range Rovers although have had a couple of Disco's in the past.

I thought my air-con was working quite ok. Rangie used (sadly) mostly for city commuting. Recently had to make a trip south towing a trailer & car and found that when cruising along the highways the air-con began to blow warm air. Tried a myriad of manual settings but nothing worked and in the end we put the windows down. Upon returning and resuming the city commute the air seemed to resume normal behaviour.

Any ideas out there?

Dusse
MY10 Vogue V8. (Petrol).

While you are on the motorway there is a huge amount of air passing through the condenser (radiator at the front with refrigerant) which means that the high pressure side won't be getting as hot (pressure will be lower).

This means that when the refrigerant (now a liquid) gets to the TX valve it will be cooler than when driving around town. I can confirm my old TD6 runs the compressor less during highway driving - you will have a variable displacement compressor which should be running at a lower capacity - this can be confirmed with a good diagnostic tool.

Given that it works after a short rest, it sounds like something is freezing.
** Q: when is starts blowing warm air on the highway, if you turn the AC off for a while and turn it back on without stopping the car does it come good?? If it does than something is freezing and defrosting, if not, than I would point to a sensor that is resetting with a car restart...

The operation of the refrigeration system needs to be confirmed first, it could be either

a: Low refrigerant gas.

b: moisture in the system causing the TX to freeze. Has the system worked fine until now? if it has than this is doubtful - to get moisture into the refrigerant system it would need to be leaking or opened recently. Inspection of the drier will confirm.

c: RCV valve is sticking or the internal washboard is sticking. When the ECU instructs the compressor to operate at a reduced function, it can't. As it tries to operate at (say) 30% the valve sticks in the 0% position. This however is odd as when the cabin warms up the ECU should increase compressor output until it works, giving you no AC until it get uncomfortably warm, then freezing air, then no AC ect ect.

With diagnostic gear there are some outputs to check.
*does the compressor output level request from the ECU line up with the increase (or not) in pressure measured on the recharge gauge?
*does the ECU refrigerant pressure (ECU monitors high side) match the recharge gauge.
*does the evaporator temp reading make sense, and is it getting too low (below 2deg)? if yes see below. (need to check on the highway)
*is the low side pressure (not monitored by ECU) dropping too low. This usually causes air flow from the vents to become very week as the evap freezes over, but it may have a bypass mechanism in the later units. If the low side is getting too low it is because the refrigerant level is low and needs to be topped up. Have you had the refrigerant discharged and refilled (by weight)?
*if the refrigerant system checks out, what is the ECU asking the coolant valve to do? this let coolant into the heater matrix which will blow warm/hot air even if the refrigeration system is cooing it.

You're in BNE, wonder if my kit can see the data on a 2010 - feel free...