Greetings All,

Copied from another thread, so as not to hijack that one:

I've been working on a (long-winded) troubleshooting guide for the HVAC system. I plan to incorporate all the good advice given in this forum, but compile it in an easily followed format that covers most symptoms. In other words, if you have this, check that, etc.

One thing where I'd really like to learn more is the service bulletin to reverse the AC compressor spring.

http://jagrepair.com/images/TSB/S-Ty...fficiently.pdf

I have no experience with this, as my car's AC has performed very well. It's very possible the mod was done before I bought the car, I just don't know. My thoughts are next time I have the system open I'll investigate further, but for now there's no compelling reason.

For those more familiar with this modification, can you please describe the symptoms? The bulletin vaguely says "AC system not cooling sufficiently" and that's it. Was the problem under all conditions? Or maybe just stop and go driving?

Had the AC performance been slowly dropping off, or was it sudden?

For those who've done the mod, do you think SOME of the improvement came being properly serviced afterwards? I'm not doubting the mod helps, but do have to wonder if that was part of it.

​​​​​​​Does anybody have any pictures?

Thanks for any help and comments.

 

Great idea!

My '01 S-Type 3.0L suffered from mediocre AC performance from the day we bought it, notwithstanding annual services by a qualified AC tech. Replacement of the compressor/dryer seemed imminent, but because my AC performanc and VIN matched the TSB I opted to try implementing the TSB valve/spring fix first as a much less expensive alternative.

I'm really glad I did. The improvement in the performance of the '01's AC was dramatic and lasting. I never did replace the compressor, and it pumps out icy cold air even on the hottest, most humid days. The total cost to have an AC tech do the spring flip, install a new o-ring, and re-gas my system was less than $100 - money well spent.

My experience with the valve/spring flip on my '03 S-Type 3.0L was similar but improvement was not quite as dramatic. Eventually I opted to replace the compressor and dryer with new ones bought from on online supplier recommended by a trusted member of this forum. The new compressor has no valve like the OEM jag model and consistently provides cold air.

Hope this helps.

 

May be in the FAQs as I think Rick (joycesjag) did it.

 

My understanding is the problem that the spring flip corrects is generally poor cooling at low speeds.

 

The idea behind the mod was to cut warranty costs. Obviously, the compressor was designed to perform with the spring operating properly.

 

So why has it been deleted in the new compressors?

 

I really do not know.
The function of the spring is to provide a performance that does not depend on the revs per sec of the engine. Without it, the higher the rev, the higher the performance, so to compensate this, more on/off for the clutch.

However, my 17 year old comressor just does fine with the original setup.

 

Hope this works, I have real crappy internet connection.

https://www.jaguarforums.com/forum/s...ics-faq-55212/

Looks like you will have to cut and paste addy above.

 

Thanks for all the great comments. Keep 'em coming.

I got to wondering about the purpose of this spring-loaded valve, and the modification wasn't making any sense to me. The way I understand the service bulletin, the little piston was originally spring-loaded in one direction, towards the cover. The mod relocates the spring to the other side, so the piston is now pushed away from the cover. I couldn't get my brain around how this helped. It's almost like the valve was being deactivated. Enter serious head-scratching mode...

Then I remembered the compressor is not a Jaguar-specific part. It's made by Visteon, and is used on many Fords and GMs of that era. By expanding my search to other makes, I found a lot more info. Check out this video showing how to replace the valve, although no mention is made of flipping the spring:



The guy in the video explains the purpose of the valve. He calls it the control valve. Under light load, the valve opens to partially unload the compressor, which reduces the power needed to drive the compressor, thus reducing fuel consumption.

Hmmm, time to read between the lines. It's one of my specialties! The best I can deduce, flipping the spring deactivates the bypass mode. The compressor always runs at full capacity after the mod. Does that sound right? I'm still researching this, so am not 100% positive.

Any thoughts? I was that inquisitive kid always asking "Why?" It irritates me that the service bulletin never said what was actually accomplished by flipping that spring, but I think I figured it out.

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Yes, that was my experience. My '03 suffered from poor A/C performance particularly at low speeds, which the valve/spring flip corrected.

However even after the flip, the compressor still wasn't putting out icy cold air like I was expecting - I guess I was spoiled by the performance of my '01 - so I eventually replaced the compressor/dryer. Problem solved, and it made my wife very happy too.

 

Yes, I have another input.

Go to advanced search. Type in "compressor or AC compressor" for search term, author "Brutal" p, press search.

You will find 2-3 pages of responses, within one of those threads you will find what your inner childhood quench for knowledge will be satisfied.

Brutal explains the how and why of reversing the spring.

 

Still digging, haven't found Brutal's description yet.

Found this thread in the X-Type section, with some of your pics about this little valve thingy:

https://www.jaguarforums.com/forum/x...problem-53501/