Automotive Air Conditioning Information Forum (Archives)

iconoclast on Sun August 09, 2015 4:33 AM

Year: 2000
Make: Jaguar
Model: XJ8
Engine Size: 4.0L
Refrigerant Type: R134a Freon
Ambient Temp: 106
Country of Origin: United States

Hi,
I want to start with a general question with a properly functioning A/C system.

Use my car as an example but, want to know for any car. (2000 Jaguar XJ8).

If ambient temps over 100 degrees, car has vent temp 38-40 F while cruising. Nice & cold! When stop & idle should vent temp increase & if so, by how much?

I am not a mechanic or A/C tech. Have had A/C serviced by Jaguar Dealer tech.

Regards,

Steve

GM Tech on Sun August 09, 2015 7:43 AM

Absolutely they increase- is it desirable? No- but unfortunately, this is mobile a/c- the compressor runs at the speed relative to the engine- and if engine slows down, so does the compressor- your house unit runs at a constant (optimal) speed and can cool at the same rate all the time. Also as you go thru that drive-thru- your air flow across the condenser is dependent on your cooling fans- the biggest keys to good a/c function in mobile a/c is compressor rpm and condenser airflow- both of which can be deterred by idling.

It is every car a/c designers desire to get 38-40 degf while driving - I would never expected such a huge drop when you are at 106 degf ambient- most cars would yield 50-60 degf- so you are in great shape- I would not mess with it- if it is truly cooling like you say. Most would quote you a 30 degf drop and tell you to be happy with that- your drop is near 60 degf! While idling - I would expect to be happy with 60 degf outlet temps in your situation...

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

Edited: Sun August 09, 2015 at 7:49 AM by GM Tech

Cussboy on Sun August 09, 2015 5:12 PM

Yes, idle vent temperatures will increase some, like GM Tech said. Does your Jaguar have a belt-driven fan? If so, consider a new fan clutch.

If electric fan cooled, make sure all fans are operational.

iconoclast on Sun August 09, 2015 8:45 PM

Thanks GM Tech & Cussboy!
I have a thread on the Jaguar Forums that goes into detail.
“A/C Problems”
http://www.jaguarforums.com/forum/xj-xj8-xjr-x308-27/c-problems-145705/

Summary: A/C worked great 15 years. In July, suddenly no cold air idling but cool, not cold air cruising, It was > 110 ambient so, very uncomfortable. Brought To Jaguar & they found leak in Drier & replaced that & charged system. Seemed better but not cold enough @ idle to me. Bought $10 thermometer @ Walmart:
AcuRite Digital Meat Thermometer, 00641W

http://www.walmart.com/ip/Mainstays-Digital-Meat-Thermometer-00641W/14913168

Vent temps low 40s cruising & mid 50s idle.
I brought it back & they checked & said no leak (had added dye last time) but “somehow” was 4 oz low on Freon, their new Freon filling machine must have made an error. I tested by letting idle on my driveway for 15 min & never got below 55. I had rental Jaguar XF & did same test & vent temp 40-42 when idling. Took back to Jaguar dealer shop, 3rd time. SA brought out a temperature hand held device & we measured the vent temp (His device compared to my $10 Walmart thermometer) They were only 0.5 degree apart. He agreed much too warm idling (55-57) He said when it left the shop they had tested & was low 40s. So they will check to see if once again low on Freon & if not he mentioned; compressor, belt, clutch, etc. Jag dealer had my car all week. They found a small, intermittent leak in the low side Schrader valve & replaced both Hi & Low side Schrader valves. Now I get 38 cruising! But still goes up to low - mid 50s idling @ lights. The tech has decades of experience @ Jaguar per SA & worked on this for days so, I assume he tested the pressures on both sides & they were correct.
BTW, when testing I have used both Auto setting with temp set to achieve 74 in cabin as well as max cool/ low which has it blowing hard all the time & see no real difference in vent temp output. Either setting gets me to 38-40 in ~ 5-10 min & equally rapid rise when idle. Takes a bit longer when 109 vs 98 But, I’m very happy with vent temp when cruising.
So, I wondered if you start a car that has been sitting in sun (>100 ambient) & just idle with A/C on, can you reach low 40s? My car cannot. Mid 50s at best. I read about A/C here & other places & wondered about my fans & fan clutch & T-stat & Coolant temperature/overheating, etc. (Jaguar temp gauge is notorious for not giving early warning or accurate coolant temps.) I started car & ran A/C @ idle. I saw BOTH radiator fans run. I ran Live Test @ idle with my OBD-2 & saw ECT slowly climb from ambient temp to 194 degrees F. The temp gauge hit center when temp reached 190, running an additional minute reached 194. So, my coolant & engine is not overheating.
I test battery(In trunk) wi multimeter = 12.51 V, OK since trunk lights are on so, will not get full 12.6V.
I read about fan clutch:
http://www.autoacforum.com/messageview.cfm?catid=20&threadid=10772

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.
I assume no Freon leak or could not get to 37-38 degrees cruising.
Cruising whether 98 or 109 degrees ambient, I can get to 38-39 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. 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?

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.

End of my long summary.

So far, based on GM tech’s reply, I s/b happy & consider it fixed.

GM Tech on Mon August 10, 2015 8:13 AM

Just for giggles spray garden hose water on condenser at idle and see what vent temps do.....

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

mk378 on Mon August 10, 2015 9:24 AM

Does it have a mechanical fan driven by a belt on the engine, or are they both electric? A fan clutch is only present on mechanical fans.

Engine not overheating doesn't prove much. It takes a lot more air than that for good A/C performance.

iconoclast on Tue August 11, 2015 6:24 AM

@GM tech, I may try that. Do you expect the vent temp to drastically drop when condenser is cooled by water? Condenser is in front of my radiator, right? I’d spray from outside though the grill? I am not familiar with condensers. I always thought that was the outside of the radiator when washing car & seeing it through the grill.

http://www.autopartslib.com/1998-jaguar-xj8-refrigeration-and-air-conditioning-system-components/


@mk378, electric fans. So, I was wrong to consider fan clutch which I don’t even have & to test fans by spinning the blades.

http://www.carid.com/2000-jaguar-xj-type-engine-cooling-parts/wp-genuine-fan-assembly-8781605.html

BTW, not sure this is related but in May well b4 I had any A/C issues, I was hiking Mt. Lemmon (9000’) with a friend near Tucson & it was cold when got back to car hours after sunset so, I turned on heat & it didn’t work at all. Just fan. No warmth even after driving 15 minutes.
I virtually never use the heater here in Phoenix & when I got home I ck & seemed a bit low so I added ~ 1 pt of 50:50 coolant: distilled water mix in case that was the issue. No way for me to test heater until this winter I had mentioned to my Jag SA when 1st brought in for A/C but, when they found the leak in drier, I forgot all about it.

GM Tech on Tue August 11, 2015 7:15 AM

Spraying water from outside through the condenser will prove if air flow through the condenser is an issue. Water will cool faster and better than air- if vent temps drop, than look for a reason, such as "fluff" build-up in the fins, or between radiator and condenser......

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

bohica2xo on Tue August 11, 2015 10:40 AM

How are the vent temps if you raise the idle speed to 2500 rpm while stopped?

.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

iconoclast on Fri August 14, 2015 3:50 AM

Quote
Originally posted by: bohica2xo
How are the vent temps if you raise the idle speed to 2500 rpm while stopped?



.

110 degrees ambient stop & go traffic. Vent temp was 49.1. I stopped to park & instead idle in neutral, revving engine to 2500 RPM. SLOWLY over 2-3 minutes temp dropped 2.5 degrees to 46.6 & then held. I let off gas & let idle normally & in a mere 10-15 seconds, FAST rise & b4 ~ 30 seconds, vent temp was @ 51.5 & I ended test.

BTW, after doing this & shutting off car, my fans ran for 1-2 minutes. I think due to the racing engine @ idle in 110 temps. Normally does not do that.

Will try to do water spray on condenser soon.

bohica2xo on Fri August 14, 2015 12:28 PM

Well there is your answer. Your compressor capacity is the issue. The condenser is doing the job, as long as the compressor can provide the refrigerant flow.

A worn compressor will lose capacity at low speeds. Some vehicles never had good low speed cooling. If your vehicle originally had good cooling stopped at idle, then I would suspect the compressor.

The fans were running because the underhood temp was up - the added heat from the condenser cooling the car plus the added engine load & speed. A normal thing, and it indicates the the fan controls are working properly.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

iconoclast on Fri August 14, 2015 10:12 PM

Quote
Originally posted by: bohica2xo
Well there is your answer. Your compressor capacity is the issue. The condenser is doing the job, as long as the compressor can provide the refrigerant flow.



A worn compressor will lose capacity at low speeds. Some vehicles never had good low speed cooling. If your vehicle originally had good cooling stopped at idle, then I would suspect the compressor.



The fans were running because the underhood temp was up - the added heat from the condenser cooling the car plus the added engine load & speed. A normal thing, and it indicates the the fan controls are working properly.
Thank you bohica2xo! No one had told me that worn compressor would lose capacity @ low speeds. Yes, my car has had good capacity @ low speeds b4 although I did not ever actually measure the temperature. 15 year old car.

Today’s water test for GM tech:
Ambient = 111 degrees ! Drove around @ 40mph or 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.

So clearly I need to have water spraying my condenser whenever I stop & idle at a stoplight

bohica2xo on Sat August 15, 2015 9:39 PM

Yep. Water is a powerful refrigerant. The heat of vaporization made the system run like it was 75f ambient.

Your heat exchanger stack could be dirty on the air path. Bugs, dirt, etc. collected over a decade can rob the top 10% of the condenser capacity. The fans are still working well - the idle stress test proved that.

The miles on the car & how much you want to keep it will determine where you go from here.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

iconoclast on Sun August 16, 2015 8:46 PM

Quote
Originally posted by: bohica2xo
...Your heat exchanger stack could be dirty on the air path. Bugs, dirt, etc. collected over a decade can rob the top 10% of the condenser capacity....
I want to keep the car. So, in 15 years there probably IS debris between the condenser & the radiator. How to clean it? I Googled but no tutorials. Found a post with photos re replacing a radiator on a 2004 XJR. I have 2000 XJ8. I think 1998-2003 usually use same parts, 2004 was a major redesign. Anyway it looks fairly complex. I assume I need to remove some plastic housing over the top of my radiator but then it may be so tight I would need to actually remove the condenser to clean it as well as the front of the radiator. I just don’t know. Would be nice if I could simply remove the top plastic cover & then squirt the garden hose between condenser & radiator to clean both.
http://www.jaguarforums.com/forum/xj-xj6-xj8-xjr-x350-x358-28/radiator-question-104471/

iconoclast on Sun August 16, 2015 9:18 PM

I found the 2500 pg shop manual from a link on the Jaguar Forums
http://dl.dropbox.com/u/13224034/XJ-...Manual.pdf.zip

I D/L & will try to attach the PDF here.

page 1811 shows removing radiator/condenser assembly, so they are attached to each other & removal seems involved.

I see no way to attach anything. Maybe it is not allowed.

bohica2xo on Sun August 16, 2015 10:04 PM

The dropbox link is 404, but if your car is similar to the pics in that thread you linked to there is probably room to clean things up.

If the top cover comes off, you can inspect the space between the radiator & condenser. There is usually an inch or more between the two units.

Big bits can be removed with a piece of garden hose duct taped to a vacuum cleaner hose. You can probably tip the radiator back toward the engine a little without disconnecting anything.

For cleaning in the fins, a good cleaner like Simple Green can be sprayed in to the fins & left to soak for a few minutes. it dissolves things like bugs, and removes much of the dirt. Flush it well with a garden hose. Just be careful not to bend any fins - low pressure & high volume works fine. Cleaning from in between the two units should give you good results. Might have to fabricate yourself a 90 degree hose nozzle.

Whatever cleaner you use, be careful to flush it all out. And remember that powerful cleaners can de-gloss paint. Commercial floor stripper works great on commercial vehicles - but I hesitate to recommend using it on a Jaguar.

.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

iconoclast on Sun August 23, 2015 7:12 PM

My reply to bohica2xo does not seem to be there. I will repost & add info:

“Sorry about the 404 link. I see now that the URL has “…” apparently to save space! When I click the link in the original post on the other forum the full URL displays for ~ 1 second & the disappears as the file is D/L. So, this forum does not allow attachments?

I’m not going to spray any chemicals into my Jaguar engine compartment. If I had worse performance of the A/C & was able to visualize gunk & dead bugs that would not clean with plain water….maybe.”

8-18-15, 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.

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