The radiator fan on my 3-month old '04 recently started to come on whenever the ignition switch is in the ON (II) position (prior to starting the engine). This happens whether the engine is warm or cold. I assume this is not how the fan in supposed to work.

Thoughts???

 

It might sound dumb, but is your AC on, or the defroster w/ the AC button lit?

 

NO, all accessories are off.

 

One possibility is a faulty engine temp switch. It's supposed to turn the fans on when the engine reaches a certain temperature. Normally this happens when you're stuck in traffic.

Just a thought!
Drive Safe,
Steve R.

 

Moved to UTH

 

Are you sure it's the rad fan? Have you gone out and looked? Could it be the secondary air injection pump?

 

[QUOTE]Originally posted by xviper
Are you sure it's the rad fan?

 

"Are you sure it's the rad fan? Have you gone out and looked? Could it be the secondary air injection pump?"

Oh it's obviously the radiatior fan.
It runs whenever the ignition is in the ON position, even after sitting overnite and dead cold.

 

The fan turns on based on the radiator fan switch, not the ECT sensor. This switch is to the left (driver's side) of the radiator drain petcock. It could be shorted closed, which would cause the fan to turn on as you described.

The test is to suspend the sensor with the threaded side down in a pan of water, not touching anything - heat it up with a thermometer to check water temp. You then measure continuity with a multimeter on the two pins - there should be continuity at 196 - 203degF. The switch should go open as the water cools to 5-15 degF lower than the on temps.

Since this involves draining and refilling the coolant, as well as a deep socket 23 or 24mm, unless you are handy and have the parts and tools, take it to the dealer.