Japan???
That's one of the many places I never got to go when I was in the Nav..

/emoticons/
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(east coast based)
Does the AC come on at all, blowing slightly cool or just ambient air temperature air?
Or when turned on, do you hear screaching and burn up the belt?
When the switch is on, do you get nothing at all, not even the compressor pulley engaging?
If the compressor isn't engaging, then the power isnt getting to it to provide the energy for the clutch to engage or possibly a pressure switch isnt letting it come on. Check to be sure power (12-14 dc) is actually getting to the connector. If not, check all the fuses and wiring, including the switch to find out why not and to corect that.
If the compressor clutch is engaging yet the compressor will not turn and smokes the belt.. then the compressor is locked up and will need to be replaced.
If everything seems to work, and you are getting barely cool or possibly warm air, then the system needs to have any leaks fixed and recharged with refridgerant and the proper lubricant for the type of system you have (1988, I am thinking that's still an R12 system but then again, being in japan, may not be.. dunno..)
You can check the charge pressure with a set of gauges made just for AC systems just to be sure of the charge or lack of.
Most of the leaks I have encountered were from the O rings in connectors being dry and cracked, especially in the condensor fittings and in any inline pressure switches as their thread sealant became hard and allowed seapage.
I had one condensor that cracked, I assume from the wreck the vehicle was in before I purchased it.
That's about all I can think of without cracking the manual out but I will leave you with some safety tips, as it sounds like you are doing your own work.
Safety goggles or a face shield.. wear one.
Good leather gloves.
When working on an A/C system, ALWAYS assume it is fully charged and work safely with all the gear you need to prevent yourself from becoming a casualty.