Advice needed! How can I tell if the cooling fan relay is bad in my 04 S80? It has a new water pump, radiator,and reservoir but once the car comes up to temp all of the coolant boils out. It doesn’t appear that the fan is coming on at all.

 

There is no relay. The fan uses 3 wires. There is 12 volts coming from fuse a2, and a "turn on" signal from the Engine control unit and a ground. In the attached diagram 6/29 is the fan motor, 4/71 is the controller. The fan controller is built onto the fan and Volvo does not sell it by itself. So either the controller is bad and not turning the fan on - or the ecm is not sending the signal. The fan should come on with ac compressor use also if the pressures are high enough and it's not too cold outside and the engine is not overheating.

 

Hoonk, after reading more questions and replies in the forum I tested the fan by turning on the A/C and the cooling fan does come on but only with the A/C switched on. All of the fuses are good what am I missing???

 

Get a scan tool and view live data in regard to the signal from the coolant temp sensor. If the ECU never thinks the engine gets hot enough, it won't turn the fan on. Too cold for too long will also set a code and turn on the check engine light.

Or you simply could have a blown head gasket - where the combustion gasses are getting into the cooling system, preventing flow of coolant, and possibly keeping the coolant away from the temp sending unit. The temp sender measures coolant temp not air temp.

Does it smell funny in the coolant bottle?