A/C compressor stops running after several minutes at operating temperature

When operating normally, A/C relay has 12V+ at pin 86 and ground at 87 as expected. When compressor stops running, there is no longer 12V+ at 86. If I inject 12V+ to 86 the compressor runs and the system cools.

Manifold pressures are cycling around 30/200. I've bypassed both low and high pressure sensors to no avail. System control is manual.

I would love access to a proper schematic to see what controls the relay input pin 86 and what other sensors there may be. Of course, any expert advice is certainly welcome and appreciated.

Thank you for what you do!