As Richard suggests check if the rad cooling fan comes on when ignition first switched on and cold engine, bearing in mind we are suffering very warm weather. If it does suspect the fan relay or otter switch which triggers it on coolant temperature.
If fan does come on with cold engine and ignition on, check first the otter switch by disconnection, if fan stops you have faulty switch. Unlikely the fan relay would have failed in the on position but short to ground in its trigger wiring would be possible. Assuming its a plug in one a quick check is replacement with new matching relay.
