Radiator Fan Rattle?

[Betrivent]

When I'm at a red light, and the fan kicks in, first of all my RPM drops, which is weird because first of all the fan isn't belt powered, and second of all, isn't rpm drop the last thing the car wants when cooling down since rpms directly affect the water pump? So anyway, the fan kicks in and it's pretty loud, and the car shudders.

My question is, does anybody else have this "problem"?

[ilikerice]

Can you make it go away by doing something else? like turning on your A/C? reving your car at a certain rpm?

[willygoodness]

mine does to.
maybe the revs drop because the fan is blowing more hot air into stock airbox intake? eh?

[Betrivent]

mine does to.
maybe the revs drop because the fan is blowing more hot air into stock airbox intake? eh?

Can't be, I run a CAI and the intake is faaaar from the fan.

[BLH]

The electric fan maybe putting extra load on the alternator or the ECU that also controls the fan isn't bumping the idle slightly to compensate.
I love how my 2007 controls the fan speed by switching a big power resistor in and out of the circuit with relays.

[Betrivent]

The electric fan maybe putting extra load on the alternator or the ECU that also controls the fan isn't bumping the idle slightly to compensate.
I love how my 2007 controls the fan speed by switching a big power resistor in and out of the circuit with relays.

I'm not electrically illiterate but.. layman's terms please? :iono:

[BLH]

The ECU controls the fan. By turning on and off relays.

DC motors like the fan motor. Can have two sets of coils in them. One for high speed and the other for low speed.

Another way is to lower the DC voltage into a single high speed fan motor by connecting a power resistor into the DC feed wire to the motor. Resistors lower the voltage to the motor.
In my 2007 one relay turns on the DC to the motor through the low speed resistor and then bypasses it for high speed with a second relay.

You may want check the fan motor. If it is making weird noises. It maybe trying to use a higher DC current and the current is loading down the alternator or battery.

[CrankyOldMan]

Have you looked at the fan itself to see if the blades are damaged? Do be CAREFUL when you poke your fingers in there, as the fan can turn on even without the keys in the ignition if the engine is still hot. If the blades look clean and undamaged, then it may just be the bearings going out. I've had several computer fans that started to sound like chainsaws when they were either too dirty or the bearings were about to die.

[Betrivent]

I've checked the fan multiple times before, nto for this specific issue though. Do oyur guys' fans wobble if you try to shake it? Or is it stiff on and firm? (I haven't checked this myself but I'd like something to compare to when I do)

[syntax]

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