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Hi Poolman, (warning VERY LONG post)
Yes, the low side port is on the pipe coming going into the accumulator near the firewall on the passenger's side.
As you know, I have been having an issue with the A/C on our S90 and I ran some additional tests today trying to figure out my problem. This data may help you.
Engine OFF, compressor off, everything at ambient 70F, static pressure in HVAC system was 72 psi.
I drove the car in 82F temps for ~45 miles, stopping once. A/C was working fine.
At the end of trip I pulled into the garage (now at 80F) and left the A/C ON, Recirc ON, fan speed on 2, hood open, engine at idle speed, temp gauge set to FULL COLD, compressor ON continuously, engine fan ON continuously.
The last time the system was charged was in Sept., 2001.
I had frost just aft of the orifice valve on the chassis rail for a couple of inches until it bends upward to go into the firewall & evaporator, but the line was cold all the way into the firewall. The line coming out of the firewall & evaporator was cool.
Operating low side pressure under these conditions were ~30 psi. The pressostat is set to turn the compressor on at anything over 45 spi and off at 23 psi. Again, the compressor and the engine fan were running continously at idle speed.
I checked the dash vents for temperature with a digital gauge inserted into each vent.
Driver's Left = 32.5F
Driver's Center = 39.1F
Passenger's Center = 38.3F
Passenger's Right = 33.5F
The Volvo spec is 41-46F at 86F ambient.
Frigid to say the least. (in the shade of my 80F garage).
I haven't found a relatively inexpensive scan tool that can read the high side pressures.
(Ahaaa!) I have found that when you shut the engine off, the servo solenoid that controls the heater control valve de-energizes and dumps the vacuum keeping the heater control valve closed! So the HCV opens. Now the engine is off, but, thermodynamics being what they are, the hot coolant circulates thru the heater core much like a old Model T did (without a water pump). This will heat up some of the HVAC plumbing in your dash. I always wondered..... why on a hot day after I restart the engine I always got VERY hot air coming out of the dash vents for 10-15 seconds or more until the fan cooled the vents off.
I have now installed an additional vacuum check valve in the line to the HCV. It will hold vacuum and keep the HCV closed for several hours after shutdown. (I may have to remove it in the fall when you may go from A/C to heat in the the same day).
(Poolman, I know your very experienced but others will read this so I am going into far more depth than I normally would. Please pardon my verbosity).
By far, the absolute best way to charge the system is to evacuate, vacuum test and then only add the exact amount of R134a and PAG oil.
If your system keeps loosing it's charge, you have a leak/problem and need to take it to a good shop.
If you believe your system is tight, and just needs a 'topping off' after several years since the last top off, then the following procedure may work for you.
I highly recommend AGAINST using any R134a that has a STOP LEAK in it. You don't want to gum up your system or plug your Orifice Valve. If you need a Stop Leak then you have a leak and it needs to be repaired.
Now, that being said......
(Some on this board may/will not agree with the following)
I have found the following (unapproved) backyard, shadetree, method to work very well on all vehicles I have used it on. WARNING : I am not a trained HVAC technician nor an ASE certified Volvo mechanic so perform this at your own risk!). If your uncomfortable doing this, take it to a good shop.
All you need is a temp gauge, note pad and low side pressure gauge (available for ~$20 at Wal-Mart).
Check your static pressure as I described above FIRST!
Ambient here means the engine AND surrounding air. (I.e., the car has not been run).
At 72F ambient, R134a should be ~ 74 psi.
At 82F ambient, R134a should be ~ 91 psi.
At 90F ambient, R134a should be ~ 104 psi.
At 97F ambient, R134a should be ~ 118 psi.
If static pressures are HIGHER than these values at the ambient temps..... DO NOT TRY TO ADD R134a, you are overcharged.
Note : R134a systems are very sensitive to pressure, much moreso that R12 systems. It is better to slightly underfill and R134a system, then to overfill it.
The purpose of this procedure is to only add as much R134a as your system needs, NO MORE!
Start the engine, turn the compressor ON, recirc ON, temp control to FULL COLD, fan speed 3 or higher, hood open. Your fan should be running continously and the compressor should be running continuously if the ambient temps are ~80F or higher.
Insert the temp gauge into the center, dash vent. Wait till the temp. stops dropping (a digital gauge works best here, easier to read and you can pull Hi/Lo temps). If the temp gauge is 41-46F or lower, you are in very good shape and shouldn't add any R134a.
If your dash temps are higher than the above spec. you can connect a can (UPRIGHT) of R134a and open the valve. Get in the car and run your engine rpm up to ~2,000 rpm and watch the temp gauge. If the temps don't go down any lower than what you had, STOP, return engine to idle rpm, close valve on can and remove. You may have another problem and a proffesional needs to look at it.
If the temps at the center dash vent start going lower, keep the rpm at 2000 rpm and when the temp gauge STOPS going lower for about 30-45 seconds, return the engine to idle, close the valve on the can and remove the can. That's the best you can do.
This has worked for me many times.
I hope this helps.
DEWFPO
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1998 S90 077,400 and 1995 964 154,100
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