1995 Legacy L (A/C problem)

[John]

My 1995 Legacy works great except for the unreliable A/C. Most of the time
when I set the thermostat all the way to cold and press the A/C button, the
A/C works fine. There are other times when the A/C refuses to work. When
that happens, the A/C will usually come on in due time. This problem has
been going on a year or so. Any suggestions would be greatly appreciated.
Since this problem is not consistant, it is hard to diagnose.

Thanks.
John