A/C: Normal pressure on low side, low pressure on high side?

[98K35Ox]

Would anyone know if this points directly to the compressor being bad, or if there is another possible issue?

Truck is a 1998 GMC K3500. AC compressor comes on and stays on when the AC button is pressed and max fan speed is set in the truck. When driving on the highway the truck stays cool, but when idling the AC quickly warms up to about 60-70 degrees at center vent. Outside temps are from 90-95 and humidity is around 50-60 atm.

When we checked pressures today with a set of gauges (after letting the system run for about 15 minutes) the low side reads 45psi and the high side reads 133psi.

Any way to further troubleshoot whether it is definitely the compressor or just low in coolant?

 

[chipskittles]

It doesn't sound like its low on refrigerant. You would have a low low side and the compressor clutch would short cycle. It's not doing that. Your high side is very very low. Airflow is a concern since the main issue is at idle(sitting still I assume). No airflow from a worn out fan clutch will normally cause lack of cooling, but it will also raise high side compressor pressure.
Based on the fact that your system is still "working" in this configuration, it's probably not airflow causing this.

It could also be other things, such as contaminated charge. if there is a lot of air in the system it can exhibit the symptoms and gauge readings you describe. A restriction in the system, which would most likely be caused by a failing compressor, could also cause these symptoms.

I agree, from your information, yes, it's probably a worn out compressor.