Auto Air Conditioning & Heater Repair: 94 Full Size Blazer Lukewarm, size blazer, gauge readings

Question
94 Blazer 350cu.in Problem: Warm air, compressor cycling on off every 3-4 sec. added r134 half can ,compressor runs steady, slightly cooler air from vents(not nearly cool enough)gauge readings: engine off
low 115 high side120...compressor on ,a/c on, low 48 high side 148 (psi). also, when I pulled gauge off high side valve leaked until I replaced cap. Guys like you make the world a better place Tom, Thanks alot

Answer
You stated: when I pulled gauge off high side valve leaked until I replaced cap.

This means that the schrader valve (just like is in your tire stem is leaking) and your losing freon from this high side valve. the only way to replace it is to empty the system of freon and unscrew the schrader valve and replace it just as you would for your tire stem.

Your pressures are a little low on freon.