Radiator fan only works when ac is switched on – car talk – nigeria gas 47 cents

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Radiator electric fan has a trigger, apart from A/C compressor switch. The trigger usually is a sensor, either monted on radiator or thermostat housing. Please, dont misplace the temperature sender & CTS as the fan sensor trigger. Though, in some brands or cars, the CTS also serves as the radiator fans trigger. I dont know the electric system of Japs.

Check if all the sensors on thermostat housing or radiator still have their wiring connectors/sockets well plugged in. Start the car, allow it to idle till the needle on the temp guage reaches middle of the guage. If the needle starts to exceed the middle of the guage and the radiator fan doesnt start spinning, then the fan(s) have lost trigger. Either the trigger sensor/switch has failed or the connection is lost somewhere/broken wire/failed relay or blown fuse.

Have you tested to be sure the thermostat still opens? When the temp guage is about to reach the middle, the lower radiator hose should become warm or hot, just like the upper radiator hose. When that happens, it means the thermostat valve has opened to pass hot coolant into radiator, while the water pump flow in cooler coolant into the engine walls from the radiator before the thermostat valve closes up. But if the lower radiator hose still feel cold when the temp guage needle is at the middle, then your thermostat is stuck closed. It will need to be replaced, before it blows off your head gasket.

But if the upper and lower radiator tube/hose feel the same from when the engine is started cold till when it warms, then your thermostat is absent.i.e. your thermostat has been removed, meaning, be ready for engine replacement or engine rebuild soon. Goodluck.

Radiator electric fan has a trigger, apart from A/C compressor switch. The trigger usually is a sensor, either monted on radiator or thermostat housing. Please, dont misplace the temperature sender & CTS as the fan sensor trigger. Though, in some brands or cars, the CTS also serves as the radiator fans trigger. I dont know the electric system of Japs.

Check if all the sensors on thermostat housing or radiator still have their wiring connectors/sockets well plugged in. Start the car, allow it to idle till the needle on the temp guage reaches middle of the guage. If the needle starts to exceed the middle of the guage and the radiator fan doesnt start spinning, then the fan(s) have lost trigger. Either the trigger sensor/switch has failed or the connection is lost somewhere/broken wire/failed relay or blown fuse.

Have you tested to be sure the thermostat still opens? When the temp guage is about to reach the middle, the lower radiator hose should become warm or hot, just like the upper radiator hose. When that happens, it means the thermostat valve has opened to pass hot coolant into radiator, while the water pump flow in cooler coolant into the engine walls from the radiator before the thermostat valve closes up. But if the lower radiator hose still feel cold when the temp guage needle is at the middle, then your thermostat is stuck closed. It will need to be replaced, before it blows off your head gasket.

But if the upper and lower radiator tube/hose feel the same from when the engine is started cold till when it warms, then your thermostat is absent.i.e. your thermostat has been removed, meaning, be ready for engine replacement or engine rebuild soon. Goodluck.