I was looking at the Chevy shop manual this morning and found some interesting stuff:
1.) The A/C System Performance Test table says that with an ambient temp of 75 degrees, the STATIC pressure should be 70 PSI. I didn’t record a STATIC PSI for the Impala AFTER charging, but I did for the Taurus and it was 78-79 after charging the first can (or very near ambient). I’m going to check the Impala again. I’m guessing it’s going to be in the proper range.
2.) The A/C Performance Table (Temperature based) says that at ambient temp of 76-85 degrees F and Relative Humidity of 35-60% (my Weather Channel electronic indicated 47%, but I doubted it’s ambient temp, so who knows?), the Low Side should be 31-42 PSI and the high side between 148-195 PSI (with a maximum left center discharge air temp of 60.8 F). I think I’m in the ballpark of these numbers right now.
3.) The A/C System Pressure - Zone Classification graph seems to indicate that at a Low Side Pressure of less than 35 PSI and a High Side Pressure of about 200 PSI, I’m in Zone B on the graph - which leads to a Diagnostic chart with a LOT of steps and verbiage. Maybe I should try to plow through this to see where it leads me. The problem with these tables is, whenever I’ve tried to use them, I usually hit a dead end because I don’t have the proper equipment (eg: “hook up the Rotunda”, or whatever it’s called …)
So - I think what I’m going to do next is buy a couple of thermometers to measure the vent temps in the cars. The manual says to use TWO at the same time - measuring the left and right vents at the driver’s cluster while running the car at 2000 rpm for 5 minutes. I was thinking not only could I do that, but maybe I could stick one in each car for a short-term test to see what that might reveal. Then, maybe I’ll buy another can of refrigerant if that’s what the diagnostic table leads to (this time with the PAG oil - both cars use PAG according to the manuals).
One question though: The Taurus has a tach on the cluster, but the Impala doesn’t. Can I just use engine sound to approximate 2000 rpm on the Impala (by using the Taurus), or do I have to buy a tach. And then how does one person maintain 2000 rpm - by manually manipulating the throttle linkage under the hood?
Also ran across some verbiage in the Impala manual that mentioned the possibility of dye incompatability: “Not all of the R-134a dyes are compatible with PAG oil. Some dyes decrease the oil viscosity or may chemically react with the oil”. It also said, “GM passenger cars are now manufactured with flourescent dye installed in the A/C system …[use GM dye J41447] and follow the procedure for vehicles that do not already contain the dye”. Funny - this manual is for the 2002 Impala/Monte Carlo. You’d think they’d be able to give a definitive statement as to whether these cars have the dye already in them from the factory or not (instead of the generic statement that they undoubtedly cut/pasted into ALL the manuals).