When does second radiator fan come on?
 

Hi all,
I've had an overheating problem and am diagnosing why the second fan (drivers side) doesn't come on. Some posts say if AC is turned on, both fans should come on. Only my primary fan comes on with AC. Some posts say one is triggered with the AC and the other is triggered based on coolant temp.

Hooked fan to battery and proved wires and motor are good.
Swapped fan relays - no change.

Primary fan comes on with AC but no second fan. Ran car up to temp (engine temp of 215), pulled over and checked under hood. No second fan running.

Is there any way to validate proper operation of the second fan while car is sitting in the driveway?

Thanks for any help.
Keith

There are two fans, one for engine and one for AC.

The engine fan will come on once you have reached an "overheating" condition. The specific temperature triggers are listed in the FSM, however it does not come on with only AC usage.

The only way to validate is to either replicate the engine heating conditions to trigger fan, or have some type of ECU tuning software that allows you to manually turn the fan on.

-alex

This problem was pretty common with the Mk5 Golfs. It was fixed by replacing the secondary fan (my old Golf GTI) or both fans (my friend's old Golf S). We weren't able to monitor the fans with RossTech VCDS (if there is a parameter to read, I wasn't sure where it was), so I'm not sure if Toyota Techstream can monitor the operation of the fans.

Pretty easy to test on a very very hot summer day with the car parked and engine started. The primary fan should come on after the engine starts, and then as soon as A/C is turned on, the secondary fan should come on.

Thanks Alex. Do you think its just the coolant temp that triggers it or are there other factors involved to signal the 'overheating condition'? I read somewhere the stock activation temp is 212f. I just took the temp up to 217 in the driveway with hood closed and the second fan remained idle.

Tried the AC on as well with high coolant temp. Primary fan spins on full but second fan stays idle.

217F isn't really "overheating"... my experience with overheating is usually in the realm of over 105-107C.

It's triggered by coolant temp, and usually some combination of ambient temp + vehicle speed. I don't have access to the ECU code, otherwise there would be a more definitive answer.

-alex

@krl, have you checked the RDI fuse? I'm bringing this thread back as I solved this same issue I had on my car. Both fans should turn on with AC on.

I experienced Fan2 (driver side fan) never getting enabled. Fan1 (passenger side fan) would go on with AC and when overheating. I swapped in spal fans w/ shroud since I thought Fan2 motor died. Fan1 worked for a while, and then stopped working with AC. Realized 2x 25A fuses were blown, RDI and CDS. RDI is Fan2 and CDS is Fan1.

Now both fans turn on with AC. It's odd the BRZ wiring schematic doesn't include these fuses in the diagram for the radiator fans, but includes the relays.

I think you were pretty close with what you've done already.

If you go out for a drive on a hot day, go for a nice brisk drive and get it up to temperature. After about 30 minutes, come home and park it in your driveway and leave it idling. Turn off the air conditioning.

At this point, you shouldn't hear any fan running. As the car heats up since it isn't moving, the second fan should kick on (depending on ambient temperature, I would guess 10 minutes or so). Once it does, turn on the AC and then both fans should be going.