August in Charleston, SC can be pretty brutal. I noticed the AC in Guzzler was not ice cold so I wanted to work on the system a bit.
The first thing I did was stick a meat thermometer into the AC vent to see what my starting temp was. At idle I was only getting down to 74 degrees. I know that it definitely gets colder than that (I have measured it before and saw mid 60's) so I wasn't exactly sure why it was running hotter now (see the bottom of the page for an update):
After getting a starting temp I wanted to bleed out the old R134A. I grabbed my Harbor Freight A/C Manifold Gauge Set ($30 - Item #92649). You hook the blue hose to the low pressure side of the system and vent the pressure out the yellow hose:
They say that R134A is bad for the environment and you should always vent to an appropriate vessel. In this case I used an old Bud Light box. Note that I do not have the red hose hooked to anything. That is used for the high pressure side of the system but it wouldn't fit on the car for some reason. I know it fit on there a couple of weeks ago but it wasn't today:
After most of the pressure was gone I hooked up my Harbor Freight vacuum pump ($13 - Item #96677) to the system. The yellow hose is from the gauge set and the blue hose is from my air compressor:
I started the compressor and watched the gauges. You could see it was pulling a pretty good vacuum so I let it run like that for about 45 minutes:
After pulling the vacuum I was getting pretty hot and sweaty (it was a horribly humid day) so I stopped taking pictures. I had no idea how much freon to put in the system and I was really scratching my head at this point. I had two 12oz cans of R134A I bought for about $10 each at Advanced Auto so I just started putting them in. Note that you should have the car running with the air set to high while filling with R134A. They always say to keep the can upright while filling so I take a velcro strap and wrap it around the fill trigger so I can walk away instead of standing there for 10 minutes while it is filling. After one full can was in the gauge that came with the can said that I was at 45 PSI. The gauge also said that a 25-45 PSI range was a full charge. I stopped after the first can and jumped into the car. It was immdediately apparent that the AC wasn't cooling much. My meat thermometer showed that I was only at 78 degrees. Heck, that was worse than what I started at. Hmmm, maybe two cans was what was needed. I know the system was working fairly well before and the gauge that came with the cans showed about 70 PSI before. Again, I was very puzzled by the numbers I was seeing. Anyway, I started putting the second can in so I could see what difference it made. After the second can was in I was around 70 PSI again and the air coming out of the vents was no colder (still around 78 degrees). I was pretty upset and started removing all the gauges/hoses from under the hood when I saw a small sticker that said "R134A - .55 (1.2lbs) min --- .65kg (1.43 lbs) max". Since the cans were 320 grams each this meant that two cans were indeed the correct amount to refill the system. I jumped in the car and went for a quick drive. As soon as I got the RPMs up the air coming from the vents dropped to 62 degrees. That really isn't very good but it is much better than 78 degrees. At this point I am not sure what is going on with my AC system but it does at least have the correct amount of fresh R134A. Until I can get the red "high side" hose on my gauges hooked up to the car I am kind of flying blind. I'll leave it alone for a while and see if I come up with anything else.
UPDATE: It turns out that the AC in a Geo Metro needs to be running faster than idle in order to get the compressor turning fast enough for adequate cooling. I have seen the vent temps as low as 46 degrees (on a hot Charleston day) when driving on the interstate. I'm wondering what an overdrive pulley (oversized AC pulley so the compressor turns faster) would do for me.