Volvo 850 a/c system: what to do, what not to do

[JimBee]

Further comments?

[thinkoutside1]

This has all been very helpfull. Thanks everyone. I have some questions when refilling a completly evacuated system (I'm installing a new compressor valve and dryer...
1. The middle hose on the gage set that you attach to r134a refill bottles is not under vacume so I have seen many people recomend you bleed this hose by opening the middle valve after the refill bottle is attached for just long enough to see a small amount of the r134a be released. Then you will know that the line no longer has air in it. After bleeding out this air you can open the low side and begin filling the system. If you are using the cans size to measure how much r134a you are adding how much r134a did you just loose to the atmosphere? my best guess would be maybe 1/2 oz.
2. Do you need to add any additional oil if the r134a has oil in the refill mix?
3. I have herd that the stop leak additive in refill cans can actually be bad for your system. Is this true? The problem is almost all refill cans sold in store now have stop leak, die and oil in them.
4. How do you know what amount of an 19oz. r134a can is r134a vs. all these other additives. I worry that if I add 2 19oz (I have a XC90 with rear ac so I need 37oz) that maybe only 17-18oz of that is actually r134a so I may end up under filling the system.
5. Can you mix 2 brands of r134a? I assume yes. It may be best for me to get 1 20oz can of one brand and a 18oz can of anther to get closetest to my desired fill weight. Thoughts on this?
6. Does the 2007 XC90 V8 have a high side port? Isn't the big port right in the radiator next to the low side port near the front passenger headlight?

[abscate]

I loosen the middle fitting after I attach the can but before you open the blue valve, until I hear a slight hiss at the fitting. That’s enough to blow the air out, just for a second.

You need a total amount of oil in the system. Volvo gives a table of how much to add for each component replaced in VIDA

STOP LEAK IS BAD. don’t use it

You can mix brands. It’s all the same stuff. It’s up about 3x In price from last year.

Your AC will work from about 70%- 110% “ correct charge”. There will be a narrow window at the best charge where you will get the best temperature delta of 40 F or more, you can get 30 degrees delta over a wide range.

In hot climates, you want a bit undercharged.. in cold climates, a bit over charged.