I have 1989 740T with a noisy A/C clutch- not gone, but making "fix me" noises. The car stil uses old freon, so I am going to change over to new coolant gas when i go to work, and add a variable orifice. I see a few things that can be done- some covered in the FAQ- from basic changing the clutch bearing to getting a direct replacement rebuilt to upgrading the compressor to a better type. I read about the need to completely remove all oil from the compressor and system, so this is question #1- if I choose a simple clutch replacement, is it worth the time and effort to drain the old oil out and reuse the compressor? It works fine, btw, just needs coolant- but it is old. And number 2 is about a better compressor- anything that would bolt in that would be an improvement?
Any advice, opinions, caveats?
thanks

R

Hello,
If you'll look up the FULL specs of both PAG and Ester (100) A/C oils, I think you'll be plesently impressed that the cheaper of the two is the better of the two. PAG oil will NOT mix with your old mineral oil, and to use it, you really need to get as much of the old oil out as you can (mineral oil does not suspend well in R134a.

Ester (100) oil (polyester based and available @ any parts store, comes in most aftermarket kits) will actually mix with your old mineral oil and keep it suspended in the new refrigerant. It's also a MUCH better lubricant with much better viscostiy scores. To use it, you simply flush out the system with a cheap can of flush from your local parts store,,,,,,,,,.........,,,,,,,, EXCEPT the compressor, disconnect the hoses from the compressor and leave whatever oil is in it there.

The only change I've made on ANY of my Volvos is the desicant (reciever/dryer). The desicant in the original system will actually absorb PAG or Ester oils, which not only reduces the amount of oil availble to the system, but also (and more importantly) will not allow the desicant to do it's job and absorb moisture (Deadly to an A/C compressor).

My 740 has had over 100k since the conversion and my wife's has nearly 60k, I've had only ONE hose blow and it was in poor shape to start with. Was on my old 78 245 and still lasted nearly a year (southern heat, so MUCH a/c useage).

Hope this helps somewhat,
Frank

PS: There is the argument that "If Ester's better than PAG, then why would the auto industry go with PAG?". Well, First off, the Big 3 set the pace in defaults since it's now tied to almost every single forien company out there..........

The 1st release GM 700R4 was leaps and bounds a better transmission than any of the series to date. Why would they do that? Why go backwards to a less reliable part? Easy question, look up "engineered obsolescence". You can also find the full story of PAG vs. Ester. Both are good, Ester's better in all cases and MUCH easier in conversions.

Thanks this is helpful info about the two types of oils. A question: You mention that the compressor does not have to be emptied if I use Ester 100 lubricant. I am assuming that this is newer info that what is on the FAQ. (this is why I'm asking around- newer specs, lubes, etc,). If the present clutch / compressor proves to be OK, Would I gain anything by emptying the compressor? Did you use a variable orifice on your cars?
Thanks

"Would I gain anything by dumping the compressor?"
It would help get any further 'trash' out of the system.

"Did you use a variable orifice on your cars?"
I used the original and only changed the reciever/dryer.
The Volvo condensor is a pretty efficient one to start with, so it redily transfers the heat from the system to the outside air. High side line pressure is well within range. An expansion valve is almost always going to be a plus over an oriface tube.

Long story short. If too much heat remains in the refrigerant AFTER it's already been through the condensor, 'line pressure' will go up. When line pressure (high side pressure) goes up, the pressure held on the compressor (head pressure) is up. Eventual failure.

OK, that's what can happen with any system and what often happens with an R134a retrofit. On your car, the design is so that it's not nearly the concern of most older cars. In short, the factory system (PLUS a R/D swap) is well @ home with R134a.

Frank

Very good general info type article on ac 12 to 134 conversions. www.delanet.com/~pparish/gen-rp.htm Here in So Cal I was very surprised to find that R134 had suddenly gone up to $12.99 a can!! I know we're paying 30 cents more than anyone else for gas but an overnight 100% increase is hard to figure.

Remember, too, that 134a is very cheap. Proceed with little fear of experimentation, "trying your luck" with the old compressor, and keeping your current hoses.

If something goes, it's just a mechanical swap out, suction and refill.

A local independent Volvo shop stayed away from the expensive "replace everything"
scare when the conversion craze got going a fewe years ago. This is when you were being told the R12 hoses couldn't handle the higher pressure, or were not barrier hoses needed for 134a.

They merely purgedd the R12 and oil, evacuated, and filled with 134a and its oil.
--
'Can't understand why people abort Volvos, either' '89 740 Turbo, 122,000 miles

You can replace the clutch without removing the compressor or opening the sstem, buy you could buy a whole new compressor, and an upgrade at that for about the same price , so.....
Check these folks out, their price on a new 709 is about the same as a clutch from most places, and that 709 makes my 240 wagon into a freezer ( the 709 is a larger capacity , more efficient compressor than the stock ones, and ironically it puts less load on the engine )
http://www.nostalgicairparts.com/COMPRESSORS.htm
And they have everything else that you might need nd are very helpful
--
-------Robert, '93 940t, '90 240 wagon, '84 240 diesel (she's sick) , '80 245 diesel, '86 740 GLE turbo diesel, '82 Mercedes 300SD for sale

Thanks for the tip- for that little money, it's not worth the trouble of replacing the clutch, and, like you said- the 709 is a better comprssor.

R