96 E320 AC poor cool at idle

[bradxj]

Does not cool well at idle. Works fine going down the road. Lo side pressure seems high at 46- 49 psi. I have evacuated and recharged the system so I dont believe it is a charge problem. It has a variable compression ratio compressor, I want to know how it senses heat load and adjusts the swash plate angle inside compressor. Will be greatful for any help, thanks