Cooler fan does not run

Hi guys, I noticed now in the heat that the radiator fan doesn’t start in our car. Car is a V70 I petrol bj99 with air conditioning. The air conditioning hasn’t been running for a while. The coolant temperature on the display never goes over the middle, remains rather below. That’s a bit strange, because that’s how it is in the traffic jam, the temperature doesn’t have to go up there if the fan doesn’t run?. Temperature goes relatively quickly after 3-5km to just below the center. Heating is running, cooler hoses are all warm as well. How do I best check what it is or what can I replace? Or can I somehow connect the fan so that it runs permanently? Would be better than not at all.- Greeting Carni