Oil presussure warning light when A/C is on (Shogun)

I hope someone can help me figure this out, any suggestion will greatly be appreciated.

When A/C is put on after driving for for a while very hot wheather, the Oil Low Pressure Warning light comes on & the the steering power assistance is partly lost ie: the effort to get the vehicle moving increases, I have to push harder on the accelerator.

The vehicle temperature gauge also moves up considerably.

(The Vehicles rear A/C is permanantley blowing hot air even when the fan is on & the A/C is off. I have just had the A/C regassed and the tech explained that the R12 had been replaced in the front but it seems as if the rear was simply disconnected and would probably need a more expensive gas and need to be done separatley, he had no explaination for the hot air blowing, so I just had the front regassed.

The strange thing is when the A/C is turned off the vehicle handling returns to normal :confused: but I am just worried as the Manual says when the light comes on take to the dealer, but the I have spent about £200+ and the dealear isn't telling me anything definitive


PLEASE HELP