Don:

On mine, the service ports on the back of the compressor are under plastic screw-on caps, and when I removed the caps, you could hear a hiss of escaping refrigerant. If you have a leak at a hose fitting, it may be a bad O-ring.

I didn't really look too closely at the pipe coming out of the condenser. It looked like a service port, but it was also covered with undercoat material and I didn't mess with it. I think the entire receiver dryer is part of the high side, and so any fitting would be a high side fitting, although I may be wrong about that. Anyway, on mine, there is a port which points almost directly toward the passenger side A-pillar. The Schrader valve here was leaking, too.

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Mike W., '91 744T 191K, Largo, FL