Anyone with a P1 should consider replacing the heater hoses before they fail. Same thing with the radiator hose above the transmission. The plastic T connect will crack/leak. The coolant bottle will crack open due to age, heat and pressure. Replace if original. There is not any coolant level sensor on any P1 Volvo. Parts pics are from ipdusa.com 2005 Volvo V50 Heater Is Not Working? RepairPal will help you figure out whether it's your Heater Blower Motor, Thermostat, Heater Blower Motor Resistor, or something else. When I reconnected the controller to the four prong plug under the dash and check the output to the fan at the two prong connector I get a steady 12 V regardless of whether the fan switch is on or not, and even if the key isn't even in the ignition. If I then plug the fan back into the controller it doesn't spin and I get 0 V at the fan terminals. W4aLsH.