2004 Accord EX sedan 4 cyl

Both fans come on with the windshield defrost setting and a/c setting. The radiator cooling fan isn't coming on by itself though. Let it warm up for about 20 minutes. Checked all the fuses, jumped the relay and fan comes on fine. The car is not overheating, it's sitting at normal temperature after it warms up without turning the a/c or defrost on to kick on both fans. Normal heat and it sounds like the thermostat/heater core is opening when turned from cold to hot.

In other words, the car seems to be operating normally, great heat and great a/c, just the radiator cooling fan isn't cutting on alone. Is it just not getting hot enough? It's strange that both fans operate when the a/c or defrost is on and everything is running fine and no over temp. I'm scratching my head. Thanks in advance for any guidance!

 

It is possible the coolant isn't getting warm enough to close the temperature switch. Does the temp gauge in the cluster get over the half-way mark? What are your outside temperatures?

Are you doing this test with the heat on inside the car?

 

Temperature is reading normal. Running it with no heat or cooling in the cabin doesn't cause the fans to kick on and running the heat and cold doesn't cause the fans to kick on, unless I turn the a/c or defrost on and then both fans come on.

 

If you have a scanner, you can monitor the coolant temperature. Above 199 °F, the radiator fan switch should close and turn on both cooling fans. If the coolant doesn't reach 199,. then the fans will not turn on unless you have the defrost or a/c turned on.

Your fan switch is on the bottom of the radiator and will have two wires going to it (green and black). You may want to check for corrosion in the connector or damaged wires. They are exposed to the elements and you could be dealing with a faulty electrical connection.