Does anyone know what the internal presure should be for the aircon system. I've recently changed the compressor, condensor and a gas re-fill. When the aircon is on I'm getting a high pitch air noise/ grinding metalic noise in the cabin, the noise can't be heard outside. The aircon is working but the noise is doing my head in. At first I thought it was the interior fan but is not that. I was just wondering if anyone had any ideas before I call the local aircon guy on Monday.

Gas is measured by weight and not pressure, if you have used one of those AC cans to get the system running then the its most likely either has to much gas in it or to little. To much gas can cause the compressor to overwork, to little can lead to no cooling. The pressure varies depending on lots of factors, that is why weight is used to fill the system.

It was filled by a machine. Think I will take it back to the place that filled it tomorrow.