Compressor high pressure doesn't increase

[jsinga0596]

2003 GMC Envoy XT w/rear air CCOT fixed displacement sanden TRAS12. Static pressure @ 100psi 85F temp outside.
compressor engages, anything over idle low side pulls down until low pressure switch shuts it off. High side stays @ 100psi and doesn't increase. at idle low side will hang @35psi high side @100psi. Vent temps are cool not freezing.
Compressor is not noisy. I doesn't have a variable displacement valve.
1st thing to do is evacuate and try and charge correctly?
Thanks, JS

[tbirdtbird]

1st thing to do is evacuate and try and charge correctly?

YES