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same deal as you. My wife's 96 850turbo had(has)the dreaded evaporator leak. We didn't fix the evaporator, I just learned how to recharge from posts on this site. (She looks much better driving the volvo than I do driving my "man-van").
On May 7th, there was a great post by Chris Herbst about vent temps, pressure etc. on the AC. (I copied at the end of this message) I can't help you with why the air is different temps from the Driver v. passenger vents, but I can tell you what I'm getting temp wise.
Before my self-recharge, I was getting 80degree air out of the vents. Not good.
After the self-recharge, I'm getting in the low 40's, higher when it's hotter, but much better than before. I know I have a slow leak so I keep my $5 Radio Shack Indoor/Outdoor digital thermometer around to check vent temps.
The post I read explained that you'll probably get lower vent temps when you are moving because of the airflow, and higher temps when you sit around.
Do a search of this site for A/C recharge or A/C questions and I bet you'll find out much more.
John Murphy
Here is the May 7th post:
The thing about low side pressure readings is that they only really give you an idea of the evaporator temperature. When the pressure gauge is in the blue zone (around 40-45psi) the evaporator is at it's warmest. When the pressure gauge is in the green zone, it is at the coolest temp. The time it spends at each extreme determines the average air temperature that comes out of the vent.
As a result, you have to hit the right balance between having the compressor on, and having the pressure around 20lbs most of the time. That's when the system is at it's most efficient. This is easily achieved by charging in warmer weather until the system stays on. If it's only 70 degrees, the compressor could still cycle on and off.
If you can keep your hand feeling the temperature of the accumulator bottle, it should run cool most of the time. If it runs warm in warmer weather, the system charge is bad (low) or the compressor is no good. If it's running cool in warm weather, perhaps sweating from the condensation, it's doing a good job.
Without the proper high side pressure gauge, there's no adequate way to determine exact charge level. The only avenue of charging is to put together a picture of vent temperature, low side pressure, amount adding, and outflow (low pressure side/accumulator bottle) temperature. Charge JUST until it gets cool on the low pressure side, and read vent temps. When you cruise around, you should get vent temp readings in the very low 40s or even the high 30s. That is a fully/properly charged system. Just remember that if you overcharge it when the weather is cool, you might not find out until something blows up when it's 95 degrees outside. That's a bad situation to be in. The best thing to do is keep the charge minimum to operate WELL.
I would hate to be misunderstood. I really believe that hooking a high/low manifold set to the system is the only way to get a proper reading on the system. But since I also believe in DIY repairs, I'm making these suggestions based on other cues you can use to figure out what is happening inside the A/C system. Plus I want to actually answer the question :)
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Chris Herbst
1992 945, 71k
Volvo shop tech
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