Thi> I'm trying to debug a problem with the AC on a Lexus LX450 Thi> (Toyota Landcruiser). On a hot day, the AC starts out cold; Thi> after some time, it stops putting out cold air. When the AC Thi> is working, I notice that the low side is in correct range, Thi> but the high side is somewhat higher.
You might also notice that the high side shoots up super high at the moment the compressor engages, then backs off. I had a problem with the symptoms you're describing and it turned out to be trapped air and moisture in the system. At first, cooling was good, but then the moisture formed ice which clogged up the expansion valve, causing reduced or no cooling and higher pressures. The fix was to replace the receiver/drier, pull a fresh vacuum and recharge.
Thi> Why are there 2 high side ports (one pointed up, one pointed Thi> down)? Which one should I use?
I'm only speculating here but perhaps some other vehicles use the same compressor mounted the other way up. You can probably use whatever port is easiest to access.
Thi> How do I check the compressor's oil on this type of car?
Few cars offer a way to check the compressor's oil.
Thi> What is a best way to clean the condensor?
The best way is probably a commercial flush solution in an air powered flush gun. If you don't have compressed air, there are flusher spray cans available. You can find all that stuff at acsource.com
Good luck and stay cool!
David