Aurion Presara air con leak

[Ike]

Air conditioner stopped working efficiently so had a pressure test by mobile mechanic who found pressure dropped slightly under test, so proceeded to check with a leak detector and sensed a leak within the cabin area. Is there a common area or component within the cabin where leaks are prone to develop?

[Tony Prodigy]

Did you use the A/C regularly prior to this issue ?

Where in the cabin did he think he found a leak ? Did he probe underneath the dash where the air conditioning unit presides ?

You have set of O - Rings on the suction pipe flange entering the TX Valve from the firewall side.  

If there is a leak on the inside component, it's going to be either the evaporator coil itself or the TX valve O- Rings. The O-Rings would be more a common occurrence.

If this is the case, then you are excused for saying "Oh My God", because if you have an internal issue, you'll have to dismantle the entire dash and centre console to get access to the air conditioner unit for the sake of two one dollar O-Rings. I just had a quick read of the repair manual for this and It's a mammoth job unfortunately. You'd have to find someone who's familiar with the 40 series Aurion and who is also competent.

Depending on how slow a leak it is, you can ask your A/C tech if there is a suitable stop leak additive he can add. This could help slow and even stop the leakage via the compromised O-Ring. 
Another solution is to inject some fluorescent dye into the system then conduct a more thorough inspection. The dye will be visible where the leak is present. You may need a camera probe for under the dash.

I hope it all works out for you. Please let us know how you go.