It maybe nothing at all to do with this, I have a 2008 Roadster that was retro fitted with Morgan air conditioning system. It has a separate on -off switch located under the dash for the air conditioning condenser fans. With the car moving at speed, the passage of air thru the condenser is sufficient to cool the air for the air conditioning to operate cold. However, in congestion or slower moving traffic (with less air movement thru the condenser) the fans have to be turned on for the air conditioning to remain cold, you can of course choose to just leave the fans on all the time. I find in temperatures above 85F with the roof down the air-conditioning (which has been recently fully serviced and gassed up) struggles to cool the car (haven't tried with the roof up at those temps) Has the air-conditioning refridgerant levels been checked, could it be low, as it does deplete over time?
The A/C on my 2013 +4 is best described as cool rather than cold despite a service, I am not aware of any fans on the condenser could those on yours be an aftermarket fit ?to improve efficiency.
