Overheating problem. Radiator fan only comes on when the aircon is on.

[shabazmo]

The car overheated when stationary or in slow traffic. It was fine on high speed motorway and country roads. The cause was quite simply a faulty radiator fan. I replaced the fan which now works but only when the aircon is on. For some reason, I am not getting a current supply to the fan when the engine gets very hot. When I turn the aircon on, the fan starts and the temperature drops very quickly. So everything is ok except the trigger for the fan when the aircon is off. The coolant temp sensor reads ok as I have checked this via the digital readout but will replace it tomorrow just to eliminate it. I have checked both fan fuses and the relay and all are ok. I can bridge the relay and the fan will work. I have battery voltage on to 2 sockets of the relay.

Has anyone had this problem before or has a wiring diagram for the cooling system.. I am completely lost for ideas.

Thank you.