Yes, the temp in the car & my comfort is the main thing. But, since I got the T-stat & can quantify & notice the large jump in temp when idling @ stoplights, I’ve been focusing on that. Nothing is wrong with the temperature sensor in the cabin & when the duct blows cold it does cool the cabin down. I’ve been trying to find out if this is normal for the 2000 XJ8. When it hits 117 here & if I’m stuck in stop & go traffic, I wonder if it will just stay in the 50’s for vent temp which I suspect will not cool down the cabin as it should. For now it seems OK. When cruising it is great! Summary is cruising whether 98 or 109 degrees, I can get to 39 degree vent temp after 5-10 minutes. When stop @ light & idle, the temp goes up very quickly several degrees in 15 seconds. If a long light can rise to low 50s!

So 10-12 degree increase vs. Cruising.

Since I had just paid ~ $700 for A/C service @ the dealer & am under their repair warranty, I want to know whether or not the system is working as it should.

More tests I have done:

I spun both my fans & they did stop, not sure if had 1 or 2 revolutions b4 stopping. But not 3. Didn’t feel much lateral movement of the blades but, the entire housing (holding BOTH fans) seemed a bit loose & moved.

The other evening I hooked up my OBD-II code reader & set it to live data to read engine coolant temp. 7:30PM, 104 ambient only reach 43 in stop & go ‘cruising’, OBD-ii, Live data ECT =203-204 & when idle & vent temp incr to 50, ECT stays 203-204!

Does this prove fans, fan clutch, T-Stat & water pump all are OK?

 

You are operating at the high end of the cooling graphs. At 104 ambient idling I would be very proud of 50 degree vent temp. Your 43 in stop n go operation says that the system is working pretty well. Bet you hit 40 on steady cruise. That's about as good as it gets.

 

You may want to try posting at autoacforums.com. That is where all the a/c gurus hang out.

 

I’m happy with anything in the low 40s & below. I can hit 38 steady cruising when ambient temps are well above 100. My concern is A/C performance while idling. I had read about fan clutch problems (supposedly if you spin the fan & it spins more than 3 revolutions, you have worn fan clutch) cause insufficient air to move over compressor during idle leading to decreased performance/cooling. So I wondered about the clutch. I also know the Jaguar temp gage is notorious for failing to indicate overheating until it is very much overheating. You rarely get an early warning of a failing T-stat for example. So, I figured (correctly?) that if my 10-12 degree increase in A/C vent temp during idling was due to insufficient air flow when stopped, there s/b an increase in coolant temp. I’m guessing here but, If I has seen a rise in ECT via live data of say 10-20 degrees, I would have suspected I had found the problem. Either the fan clutch was failing to turn fans on or increase fan speed @ idle or maybe T-stat was failing to open more fully as ECT increased. Since ECT was the same whether cruising or idling & only A/C vent temp increased, I reasoned that my fans, fan clutch, T-Stat & water pump all are OK. I don’t know if any mechanics will read this & say I am wrong & have proven nothing or that yes, I am right.

If some members, have thermometers that can measure vent temp & report that there temps also increase ~10 degrees when idling, I would think my A/C is fixed. I assume most following this thread have no ability to measure vent temp. My Jaguar SA had a thermometer gun he pointed at the vent which agreed w/in 0.5 degree F with my $10 Walmart T-stat. I’m sure that gun cost much more

AcuRite Digital Meat Thermometer, 00641W

AcuRite Digital Meat Thermometer, 00641W - Walmart.com

 

[As mentioned, I am wondering about my fan clutch & if the tech considered that.

Tomorrow & Wed it will be 112 degrees. A good test as to whether the system keeps me comfortable or not.[/QUOTE]



The fans are electric and do not have a clutch. The Compressor DOES have a clutch. If that clutch is slipping or not engaged, you will have limited cooling.
If the high side pressure and low side pressure are normal then clutch is fine.


It is "normal" to have less cooling at idle due to less airflow across the
condenser. Once the car is cooled down it should still be comfortable at
idle. My guess is your car is almost right and probably would do ok at 90
degrees outside.

 

Yes, I had learned in another forum that I have no fan clutch.
Thanks for the info re my compressor clutch is fine.

Even with >100 degrees ambient, if no stop & go traffic, I can be putting out 37-39 degree air in 5-10 minutes! @ stoplight idling, w/in 30 seconds temp increases ~ 5 & by 2 minutes 7-12 degree increase.
With S&G traffic I get mid to upper 40s & when idle can reach mid 50s.

 

This link is the 2,500 page shop manual. page 1752 to 1852 covers climate control. It takes a while to download but should be useful.








http://dl.dropbox.com/u/13224034/XJ-...Manual.pdf.zip

 

Thanks!

I D/L manual.

100 pages on climate control alone! I’ve been thinking about cleaning the condenser in case 15 years of debris is on it between it & the radiator, But page 1811 shows removing radiator/condenser assembly, so they are attached to each other & removal seems involved

 

The radiator is pretty easy to move. If I remember correctly just remove the top cross brace and the radiator lifts up. Just make sure the fans rotate after putting it back in.
With the BIG shop manual you probably already know all that. Sometimes the manual is easier than the forum. Since you have already checked the coolant temp with your
obd 2 reader, you know the radiator is fine. Getting a peak at the condenser won't
hurt a thing. In a few months nature will fix your AC with cooler weather...

 

I stopped by Jaguar Service yesterday & asked if debris could be between condenser & radiator & explained water test. He said no debris & alluded that tech checked that during all those many hours troubleshooting. I asked if tech removed condenser. He said, No, would need to remove radiator. I said I can’t see a way to see between radiator & condenser to check for debris from top unless I remove stuff. He said you can see small gap between from underneath & can blow compressed air.

So, he seems certain that was NOT the issue.

Maybe this is the best I can expect from a 15 year old compressor. I suppose it is OK. It is wonderful when I am not stuck in S&G traffic. I won’t spend well over $1,000 to get a new compressor given how well it does work now & there is no certainty that new compressor would not work the same.

 

I doubt your old compressor is performing any different from a new one. Surely the pressures would tell if it was not compressing. A bad or fouled expansion valve, too much oil, water in the charge and a host of other things can ruin performance, but I would like some of the AC smart guys to explain how an old or worn compressor could do this without bad pressures!

 

No offense, but I think you've been told at least a couple of times by members MUCH more informed than me that your idle performance is normal, and that you can't expect any better than this during 105 degree or so days...

If you choose to ignore them, I suggest you consult with the A/C experts that are nearby you for a second opinion - the dealer has already exhausted their efforts unless you're willing to just throw money at it.

R134 A/C is not proprietary to Jaguar - they are all effectively the same, regardless of maker. Go talk to your local experts.

 

@sparkenzap
You make a good point. Since it was @ Jaguar dealer 4X
1) found leak in drier & replaced & filled with freon
2) found leak in Schrader valve & replaced both valves
The tech spent many hours & had checked the pressures. If they were even borderline they would have told me that I should get a new compressor. Jaguar is not shy about recommending expensive repairs.

@QuadManiac, Not ignoring anyone. This forum &
Automotive AC Information Forum - ACKITS.COM

Had many suggestions. I did all the tests & checks I could & asked my SA about others.
Note: I tested 2 other loaner cars in the heat & BOTH had vent temps that only went up a few degrees with long idles. Not 12 degrees as mine does. So, that is concrete evidence that those cars’ A/C works better than mine after my expensive repairs. I doubt that those are magic, high performance A/C systems. My Jaguar SA sitting in the car idling with both his T-stat & mine agreed that vent temp of mid 50’s is not right. He was not equivocal about it.

At no time did my Jaguar SA or the tech state directly or indirectly that it is normal for idle performance to go up 7-12 degrees. Not once. Not even a hint of that. So based on all this I made this post.

Some people have opined that they would be happy with a temp difference of X degrees from my high ambient. No one said: “I have a T-stat & tested my vent temps & I get xyz cruising & when I stop & idle it goes up by abc degrees.”

It is OK now but, still think it worked better @ idle b4. Maybe the condenser is dirty despite comments from my SA, maybe the tech missed something. Maybe taking it to an A/C specialist & spending more $$$ would result in absolutely no better performance.

We’re just talking here.

Thanks to all who replied.

 

It seems you have an airflow problem. Car moving along highway, a/c cold; car stopped a/c not as cold. Have you observed both fans running at full speed when the a/c is on. It is simple to remove the radiator. Undo the cap on the coolant reservoir, open the drain **** in the bottom left of the radiator. Remove upper and lower radiator hoses. Undo fan electrical connections. Carefully remove air bleed pipe at top left of rad. Undo two screws at top of rad. and remove assembly. A/C condenser is not attached and will stay put. You can then check to see if there is any blockage between rad and cond, and also clean fins.

 

Here's a good primer to read on auto A/C:

Air Conditioning Troubleshooting and Repair

and attached is an external temperature vs. expected vent temperature chart that, I believe shows that what you are seeing is normal.

 

@ QuadManiac, thanks for the informative link & that temperature chart. BTW, all the many car A/C systems I’ve had in 3+ decades in Phoenix have performed much better that that chart shows in summer with frequent ambient temps of > 105 degrees! Especially on short trips 5-10 minutes many times a day & S&G traffic when it is 109 & the car had been sitting in the sun it is brutally hot & if vent temp was only 60s, I would have been in full body sweat all day & I have not been. Many of these work cars were mid level sedans such as Ford Taurus. So, according to that chart, my current 15 year old XJ8 has amazing performance when I can cruise for 10 minutes & get 39 degrees when ambient = 109! I will save that link for future reference in troubleshooting.

@fredd60, yes, I have observed both fans working correctly. I did a water condenser test as suggested by someone on
Automotive AC Information Forum - ACKITS.COM

Ambient = 111 degrees ! Drove around @ 40mph for 15 minutes but could not get lower than 50 vent temp. (I was driving around my neighborhood up & down some low traffic streets but did not take the car on main streets. So could not cruise for more than 3-4 minutes b4 turning around & going the other way.) Stop & idle in my driveway in the shade a few minutes till vent temp increased to 57 & holding. Leaving car idling, I prepared garden hose. Just b4 spraying, I recheck vent temp & it has dropped to 55 & holding. I started spraying the condenser through the grill & immediately the fan speed decreased! It was dramatic. From a very loud roar to very quiet in less than 5 seconds. I kept spraying another 1-2 minutes & vent temp dropped to 45.1! I stop spraying & get in car & now vent temp = 44.5! Still idling. I then drive the neighborhood, just on the 25 mph streets to let the water dry/drip, & even though I’m only going 20-25 mph, the vent temp dropped quickly to 38 w/in 3 minutes.

Due to my discussion with Jaguar SA (post #30) re the possibility of my condenser being dirty or having debris collected between condenser & radiator & his reply, I am not going to drain radiator fluid, remove the radiator, check for debris & attempt to clean the fins w/o damaging them….yet.

As I said, Maybe the condenser is dirty despite comments from my SA.

A/C works really great now cruising & “OK” in S&G traffic & idling. According to some like QuadManiac, there is nothing wrong, Jaguar fixed it correctly & I should be completely satisfied with these idle vent temps.

Maybe next time I need to have the radiator flushed, I’ll ask about removing it to check the condenser & clean the fins. Maybe I’ll see if those A/C specialists can do that since they probably know how to clean fins w/o damaging them.

Thanks again!

Regards,

Steve

 

Neat test using the hose - but keep in mind that the colder water temp and also the latent heat of evaporation of the water will make the condenser much colder than ambient air, at least for a short while... so you should expect to see the vent temp drop significanly, again for a short while, until sometime after all the water evaporates.

BTW, I'm not suggesting that you are 'crazy' in your attempt to get the temps down... I'm just hoping that you don't needlessly throw money at a problem that may not exist. Unless we can get some data from other Jags under similar ambient temp circumstances, we'll never really know whether your's could do better or not... but the published generic data implies that you are, at least, close to what can be expected.

I'm going to keep a remote IR thermometer in my XJ just in case we get another hot spell - it was 106 here two weeks ago... I'm now curious as to what my temps are!

 

Please post your cruising & idle vent temps here! You have the same MY as I do. I was still getting significant temp increase even with ambient 98 degrees. Even at night!

All you need do is measure temp once you think A/C is plenty cold, say after cruising w/o stopping 10 minutes & then when you reach your destination just sit in the car for 5 minutes letting it idle & watch the temp.

 

You know, elementary thermodynamics dictates that the amount of heat transferring is related to both the plenum air temperature AND the amount of air flowing. You have not addressed the air flow out of the vent, but if the fan is running fast, the air temperature would be expected to be higher than what it would for low air flow.

So, if the auto function increases the fan speed, the air temperature will rise, even though more heat is being removed. Think of it as flow vs. pressure!

And... the temperature control must be set to "lo" for it to not have an effect. That also seems to be lost in this discussion.

 

Plenum? I had to look that up, LOL

My airflow out of the vents is just fine. On Auto starts off higher & once temp in cabin approaches desired temp (74) It lowers. I had tested performance of system with AUTO vs. Lo & no difference other than on Lo fan always remains highest force/speed.

So, that is not the issue with the 7-12 degree rise @ idle vs. Cruising.