Q: My red coolant light starts flashing after driving for a while. Manual says it's electrical.

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After driving for a while my red coolant light starts flashing. Coolant is full. Manual says if car was overheating the light would stay on not flash. The radiator fuse is fine the belt driving the water pump is fine. I don't know how to check the water pump itself. I just bought this car and the previous owner said something about a sensor being bad. I'm going to try to take it to AutoZone and have it checked by the computer but any advice would be very much appreciated.

My car has 139000 miles.
My car has an automatic transmission.

If the coolant red light is flashing, then that means that a sensor is not responding to the computer system at that time. Check the coolant temperature sensor, and the coolant level sensor and make sure that they are plugged in. Remove the harness to them and check the sensor for resistance. For the level sensor, if the coolant is full, there should be no resistance as the sensor is in a closed loop. For the coolant temperature sensor, check it cold and then check it again when the engine is hot. The resistance should change. If the resistance stays the same on the temperature sensor or there is high resistance on the level sensor, then one or both sensors will need replaced. If you need further assistance with your warning lights on for the cooling system, then seek out a professional, such as one from Your Mechanic, to help you.

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