07 XK coup 68k miles. Took a 300 mile drive this weekend, AC was fine going to my destination but on the return drive the AC was not functioning properly. I had reasonably cool air blowing but I had to put the temperature down to 59 F and have the fan on full to keep the cabin comfortable (outside temp was about 90 high humidity). My AC up to this point has been very cold. I just got back and I have not checked to see if I can hear the AC motor engage as an FYI.

Suspected potential issue? Thanks!

 

It sounds as if it just needs a re-gas. Once the pressure drops too low due to refrigerant loss, the cooling efficiency rapidly goes downhill.

Richard

 

Thank you, will check it out!

 

For a deeper dive, check out the thread: Air Conditioner Question - Jaguar Forums - Jaguar Enthusiasts Forum

 

Thank you for the link! Much appreciated.

 

So I had an interesting (and somewhat disturbing) find. I was checking to hear if the AC compressor was engaging and in looking around noticed the coolant level in the overflow tank was roughly a quarter full (but apparently not low enough to trigger the sensor). I obviously filled the overflow tank and the AC returned to normal which makes sense. My concern now is, why am I losing coolant?? No puddles…. ugh.

 

The compressor is clutchless so you won't hear it engaging. It has a variable valve instead.

 

So I learned…

 

Umm, why does this make sense? I’m not following the link between low engine coolant and AC (non)performance?

 

While the AC issue certainly may be unrelated to the low coolant level, I can’t completely discount that coolant in the engine controls and is responsible for how cool the air is that enters the AC unit and as a result can directly affect AC performance. Under conditions of low coolant, too much hot air will get in the cabin raising both the humidity and temperature, which is what I was essentially experiencing.

I’m monitoring the coolant level for a potential leak and the AC system for any recurrent wonkiness, but the AC functioned normally yesterday and today in 90+ F temps after filling the expansion tank with coolant. Coincidence? Dunno. Time will tell.

 

Provided that there is sufficient coolant in the expansion tank to ensure that the radiator header is fully topped-up, and a quarter full would be sufficient, then the engine cooling will be within spec. The a/c condenser is usually mounted in front of the engine radiator therefore the cooling applied to the condenser is largely independent of the engine radiator temperature. In fact, if the engine were running hot, and I doubt whether yours was, then depending upon the how the fan/s are configured, the engine cooling fan would be running more frequently which would actually apply greater cooling to the condenser.

I am still inclined towards the system needed a refrigerant top-up.

Richard

 

Ttotally understood and appreciated Richard. I do plan on recharging the AC which is a simple step and could rule out one element in the differential diagnosis unless the issue recurs quickly indicating a possible refrigerant leak I suppose. Meh…

 

The approved procedure for topping up a/c systems, at least in Europe, is that the existing refrigerant is removed and then the system is tested for leakage before it is re-charged to the recommended weight. All this is done automatically by the machine. If there is a leak, the operator is not allowed to top up the system so you will know if there is a problem.

Richard

 

Mechanically, this makes sense. But remember those pesky microcontrollers.
if engine temp is excessive, the microcontroller can reduce both the accessory load and the aforementioned heat transfer at the radiator/condenser by "disengaging" the compressor DSP valve.

 

Sneaky coolant loss experience: had a pinhole in the 1/4" water pump vent hose. It only happened under pressure. When under pressure it sprayed a nearly invisible stream toward the cooling fan. Evaporation removed evidence.
You could smell the glycol and coolant loss was very small initially. It finally gave on the road headed to an appointment. Thus, began the cooling line replacement saga on my eleven-year-old 2011 XK.