Ford Repair: cooling system, high pressure hose, ford clubwagon

Question
I have a 1993 ford clubwagon, 350 eng, automatic with a/c. Question is, what would cause pressure to build up and blow the high pressure hose off the a/c, when with a/c off engine doesn't overheat.  

Answer
Hello and thanks for the question...I'll try to help.
There are a few things that can cause the relief valve to blow:
1: improper cooling
2: High pressure switch ...not shutting the compressor off.
3: Over charged system
4: Stuck compressor field coil and clutch.

Erik