You guys have helped me out so many times I thought I would document this in the hope someone might benefit.

Well it's March in Austin and that means hot weather and HVAC issues (and deranged serial bombers but that's off topic). First a little background. I have had a '99 Hardtop since new and completely rebuilt the AC system in 2005 when the compressor gave up and sent shrapnel through the entire system. For the past 13 years the system has worked flawlessly though I did notice I was running the fan a speed or two faster than normal last summer.

So this weekend I turned the AC on and the vents cooled down a little below ambient but really marginal. I dropped by my local O'Reillys and purchased a 12 ounce can of R134a on the way home.

After letting the car cool off I put my HVAC gauges on the High and Low tap-in locations next to the battery. BTW, high is the small line emerging from the condenser area and low is the slightly larger diameter going to the compressor. The reading for both sides was 30psi. Hmm.

Well the book says if it's between 10 and 50 it's ok but I know something ain't ok! So I fired up the engine and turned the AC on with fan full blast and got a steady 28 psi low and 120 psi high. At 70 F and 70% Relative Humidity that high side should be a bit higher than that. Also, I had temp probe in the center vent showing 69 F. That's crap!

Ok, so first things first. I looked all over the engine compartment for any sign of PAG oil. That is a sure sign there is a leak. Everythingg looked nice and dry. I tried revving the engine to see if I could get more pressure on the high side but it didn't change. Then I checked to see if the re were any cold spots on the high pressure line up stream of the expansion valve but everything was warm until right at the expansion valve where it suddenly got cold. (A cold spot upstream can indicate a blockage.) In other words normal but low refrigerant indicated.

So I plumbed my can of refrigerant to my gauges, pierced the can and cracked open the LOW side valve. Always add to the low side btw. The vent temp started to drop immediately and the high side pressure started to rise. I agitated the can slightly while keeping it upright to accelerate the transfer a bit but the low and high side stayed at 28 psi and 190 psi the entire time I was charging. The can is full of liquid that boils into gas entering just upstream of the compressor. If liquid is introduced to the compressor, well, that is a very expensive repair so don't let that happen. The vent temp continued dropping to finally settle at 43 F. Now that's more like it!!!

Once the refrigerant can was empty I closed everything up and turned the engine off. High and low side settled right at 50 psi for both.

Total cost $8.45 for R134a and 30 minutes of my own labor. No ozone was endangered during the process. The gauges I used were Mastercool Professional I bought in 2004 for about $100 but any good set will do. I consider them a good investment.