i am working on a 2010 silverado with automatic a/c. the compressor cycles on and off for no apparent reason. have replaced control head, ecm, evap temp sensor with no change. the system is fully charged any help would be appreciated

Your high side pressure could be hitting cut off usually because of no air flow through the condenser. This is typically normal.

the high side pressure only reaches 158psi this is a strange problem something is causing the ecm to turn the compressor off

Is it possible the programmer is doing this for a reason? To conserve fuel? Maybe its seeing that its not hot enough to run the compressor all the time?

Is the temperature of the output is whats causing you to investigate this?