Today my wife suggested that we take a ride to Sams Club in our 2002 XK8. For us this is a trip down to the valley, where it is even warmer than in the foothills where we live. I told her that if we took the Jag we would need to have the top down because the AC was flat (again). She said "no problem". I figured ,"big problem" when she feels the 90+ degree air boiling around her. On a whim I stopped by the local NAPA store before we left town and bought a can of AC PRO. I had seen this advertised on one of my car show channels. I installed it in the parking lot (they love it when you do that) before we left town.

In no time the AC was blowing cold,so even with the top down we were comfortable. Then I got to thinking about how my Jag tends to run warm,even when it is not hot weather and the AC is not adding heat and load to the engine. Imagine my surprise when the car actually ran cooler, barely getting over about 205. I have the RealTEMP modification, so the gauge actually reads the real temperature. I think that the AC forces the engine fans to run and that keeps the temperature down. Whatever the cause is, it is a welcome event. Now if I could just keep the refrigerant in the system.

 

We don't get too many days in the UK where we need to use the cold settings on the AC but I do get to places in the 90 deg range at least once a year.

Both my 2001 and 2005 XK8's were barely blowing cold when I got them and needed recharging. With the first one I immediately suspected a leak or compressor fault but according to Jaguar, between a 5% to 10% charge weight loss per year is normal. Anything above that is suspect.

Charge weight = 650 +/- 50 g
Compressor oil (PAG) capacity = 160 to 200 ml

Graham

 

Interesting. I've never lost any refrigerant in my XK8 and it always blows really cold. My Town & Country minivan, on tHe other hand hand, has always had issues. We capped off the rear air (sorry kiddos) hoping to fix it and now the front leaks somewhere too. We don't drive it all that much so we are limping it through the summer/fall and will look at it in the spring.

 

When I got my XK8 a few weeks ago the a/c was only blowing lukewarmish. It took about 22 ounces to get it in the normal range according to the gauge. The system only holds 28 ounces +/+ 2 ounces. It blows cold now but I only measure 56-58F at the center vents and I am guessing it should be more like in 48-54 range. To get it right I'll rent a pump and pull a a vacuum on it and put new refrigerant in it. Though it does seem to bee cooling the cabin to a comfortable temp as-is. On the plus side I've been checking the pressure with the gauge randomly and the pressure is staying the same so it doesn't seem to have a big leak anyways. I suspect the car sat a long time before I got it.


Dave

 

Hey Lanny, I hear what you're saying about the a/c and cooling fans running. I can't confirm that it's correct, but sounds like a good theory. I sometimes leave my a/c off when the top is down, but haven't noticed the temperature being any warmer than normal. I'll try to pay more attention.

Perhaps someone with greater knowledge could confirm that the fans run more when the a/c is on - other than just responding to a resulting higher engine load.

Steve

 

Don't get upset if I'm [pumping hot air] (pun intended), but when you turn the AC on, so goes the fans. They turn on also.

I think that is the way the system is susposed to work. So cooler engine water temp's also.

I believe that's why in the owners manual it recommends leaving the AC on all the time. The AC will heat or cool automatically, depending on what the outside air temp is. It also keeps the air dry and thus during the winter months, no condensation on the inside of the windows. All you have to do is adjust the temp based on how cold/warm you want to be.

The AC does cause you to use a little more fuel, but I doubt that you'll be able to tell just how much, because of so many vairables---how you drive, how much city or highway, how much you sit idleing, etc., basically. In both my 05 XJ and XK I've tried to gage just how much and finally just gave up. It wasn't enough to worry about.

Keep cool/warm.

Chuck
05/XK8 Conv.

 

When I install AC in an old car it includes what is called a trinary switch. Among other things this switch senses that the AC is turned on and activates the electric engine fan(s). I assume that the factory air in the Jag does the same.