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Radiator fan not working

2006 Hyundai Sonata Radiator fan is not turning on at temp or with AC. Fan works with 12 volts and a good ground at the connector. The car side of the connector has 14.5 volts on the positive side and 12.5 volts on the negative side with car running and AC on. Why is there 12.5 volts on the negative side and more importantly any ideas on how to resolve?

Sounds like the fan control module has failed.

Here’s what to check.

Is the 60 amp fusible link blown?

Is the 30 amp ECU fusible link blown?

Is the engine control relay defective?

Is the sensor #3 fuse blown?

Is the cooling fan relay defective?

Because you eliminated all those components when you ran voltage directly to the fan.



The 12 volts on the negative side of the connector should be normal. That’s the voltage drop through the fan windings. To go along with Tester’s suggestions here’s a wiring schematic for the fans circuits. Note that it’s considerably more complex than the old day. Start with the fuses and work your way out.

Thank you for the list to check now on tester. I am a little confused on how a blown fuse can get the voltage reading at the plug when it is not plugged into the fan.

The response on the voltage drop though the fan was a good idea but when I tested the voltage to the fan the plug was unplugged from the fan.

From the wiring diagrams, if the CONDENSER FAN RELAY 2 has failed in the position shown (unenergized) and the CONDENSER FAN MOTOR is running, you’ll see the 12.5 volts feedback to the negative side of the RADIATOR FAN MOTOR plug. Check for power to RELAY 2 coil.