I noticed my AC was acting up today. Sometimes it blows colder than others. At first, I thought it was due to the car's speed, but after a little investigation I noticed it gets colder as engine RPMs go up, regardless of the car's speed.

So I'm wondering if this is a symptom of low refrigerant pressure, or if the compressor is on the way out?

Somewhere I have a pressure gauge to check AC pressure, but I haven't used it in years. I'll have to find it and see if I'm low on refrigerant.

Anybody know air conditioners and have another idea?

 

Without operating low & high pressures you're probably just guessing.

 

+1 on knowing the low and high pressure readings. If you have not used your air conditioning gauge manifold in a long time, you may or may not have the correct fittings to connect the manifold to the vehicle.

Refer to the JTIS for the procedure, which is a free download from this forum.

 

Sounds like the spring in the back of the compressor assembly - search the form on the fix for this (after you confirm system pressures are within spec)

 

Here's the scoop, the TSB says 3.0 only but people have reported this is not the case.

 

When was the last time the AC was serviced? If it's been at least a couple of years, the most likely culprit is low refrigerant. A quick and dirty check is to place a thermometer in the outlet in the center of the dash and take a temperature reading under the conditions of poor cooling. Shut off the engine, add half a can of refrigerant to the system, and take another temperature reading under the previous conditions. If the cooling improves, you've found at least part of the problem. Slowly add refrigerant about half a can at a time. When you no longer see any improvement, stop adding refrigerant.

In my book, it's worth the initial gamble of half a can to see if you're on the right path. If there's no improvement with half a can, it's time for more indepth troubleshooting.

The official party line is to do a full evacuation and refill, but as long as there was some cooling (meaning at least a partial charge in the system, so no moisture was able to get in), you can usually get away with just a quick top-off. I've done this several times on various vehicles with great results.

Details of the full evac/refill here:

https://www.jaguarforums.com/forum/s...ics-faq-55219/

 

I would also look into that TSB.

 

OK, I'm gonna have to break down and buy a service manual for this car. I can only find one of the service ports on this thing, and my pressure tester won't fit it. I also don't have anything that will check the high side.

The spring TSB looks easy enough to change, except for the fact that the compressor isn't exactly easy to access! But you guys have given me a good place to start. Now to invest in tools and the proper manuals!

 

You can download the JTIS manual here https://www.jaguarforums.com/forum/g...rchives-65926/

The low side port is behind the left side front wheel, unless the earlier models were different.

 

you can also download jtis, alldata and jepc plus other useful files from the link in my sig

 

I'm downloading JTIS right now. Hopefully, that will answer my questions.

Is the AC system always on the left, or is it always on the passenger side? Because on the left side of my car (The driver's side on a US spec car) there's the radiator cap at the base of the windshield, the brake master cylinder & brake booster, and what looks like some spindly little manifold for the EVAP system.

The canister with the high pressure port for the AC is on the right, and I followed the metal lines for the AC all the way back to the firewall with a flashlight and never did see the low pressure port. Do I have to go in through the wheel well to find the thing? If JTIS doesn't give me some answers when I get it downloaded, I'm gonna need someone to post a picture showing me where to look for the thing, because it is apparently well hidden.

 

The low pressure fitting is on the compressor, which is on the lower LH side if the engine when viewed from the driver's position.

If you do not have the gauge adapters for the R134 fittings it may be best to have a competent air conditioning specialist check the refrigerant level and top it up as needed. The system holds about 750 grams of refrigerant in total.

Should a leak be detected, the leak must be repaired and the system evacuated and refilled prior to determining if there are other system electrical faults.

 

Look at the back of your compressor. If there is a small oval "removable" black plate with 2 10mm bolts bolting it on the repair dictated in the tsb. Regardless of model. Aftermarket compressors included. I just did this to a aftermarket compressor.

 

You got bad advice above.

NEVER add refrigerant unless the system pressures tell you to!!!!!

Trying to guess what to add based on vent temperatures is a recipe for disaster. I have seen way too many cars with too much Freon because everyone "thinks" that's the problem. More is NOT better!

Now you have a system that you have no idea how much refrigerant is in it. So you will need to drain it all out and weight the correct amount to put back in.

The A/C fitting is NOT on the compressor. Remove the driver’s side front wheel. It's located at the bottom of the sheet metal and is fairly well hidden but it is not covered up so you can see it.

Did you get the JTIS? It shows where all the A/C components are located. Well worth your time to get it installed and working.

I would replace the compressor rather than screw around with the spring on the back of the compressor. Your car is now 13 years old and the A/C compressor is worn. Plus it's not an easy place to work as I have changed two compressors, just be glad you don't have an STR for this exercise!! Check that the compressor does not have green/yellow stains or oily stuff on the bottom of the compressor. If it does your compressor is leaking.

The compressors are cheap at about $250 for a brand new Chinese one on EBay. I have been running two of these import compressors in a very hot climate for thousands of miles with no problems. Be sure and replace the dryer anytime the A/C is opened up. It’s just cheap insurance to keep as much moisture out of the A/C system as possible.
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I (finally) found the low pressure point. Extant curse words in the English language are insufficient to describe my feelings for the engineer who decided on that location.

I'm using a rather cheap AC pressure gauge from Wal Mart. Following the instructions, I had the engine at idle and the AC running wide open. The pressure on the low side was reading 80 PSI. The gauge said nominal was betwen 25 and 45. So I basically have twice as much pressure as I should.

Which tells me three things:
1) My problems are not caused by low R134A.
2) A previous owner assumed low R134A was the problem, and proceeded to "fix" the problem without checking his assumption.
3) If low coolant isn't my problem, it's probably the spring in the back of the compressor.

Now, for a little pure, unadulterated hypothesysing. When the pressure drops from the high side to the low side, the temperature drops as well. If my low side is twice what it is supposed to be, wouldn't that mean the pressure drop was significantly less than nominal, making the air conditioner less effective, especially at low compressor RPMs?

The theory is, if I bleed off some of that excess pressure and get it back in the nominal zone, my AC should work better even before I change the spring, no?

Isn't R134A supposed to be harmless to the enviroment? Can I put on a heavy glove to protech me from frostbite and just bleed the system down at the test port like an over inflated tire?

 

To answer your question - no, it's actually illegal to vent R134a refrigerant. If your showing 80 PSI on the low side - you have some big issues to sort out.

Just out of curiosity - what were the pressures on the high side? Also, pressures are dependent on ambient temperature - but 80 PSI is way off!

I would recommend taking your car to a shop specializing in AC repairs and a full evacuation, and fill to proper spec.

 

I am not sure why there is so much confusion as to the location of the low pressure fitting. I looked at three 2001 S-Type vehicles today with both the 3.0 and 4.0 litre engines and both models, still having the original compressors and refrigerant hoses fitted, have the low pressure coupling located at the compressor.

Perhaps a photo of the fitting locations can be provided if they are located elsewhere behind the LH wheel arch cover so the confusion may be cleared up.

 

The confusion was on my part. Any other car I've ever seen, it's easily accessable by popping the hood and looking between the motor and the shock tower. I've never heard of having to get down on the ground and look in the wheel well before. Whoever decided that was a good idea should be shot. Or, at least tarred and feathered.

Just out of curiosity, why is venting R-134 illegal? Is it a greenhouse gas or something? I thought they went to R-134a instead of R-12 because it was safe, and the old freon killed the planet.

 

I think the confusion is between pre- facelift (2002.5/2003) cars with the port on top of the compressor



and post facelifts with it behind the wheel

 

R134a is still a ozone-affecting / greenhouse gas but much less bad than R12.

Don't vent any as it's not good for your health either. Besides, you don't know that your car has an excess, you just know the low pressure is bad.