I am trying to troubleshoot a fan problem. Does anyone 'KNOW FOR SURE' EXACTLY when the primary fan and when the secondary fan should kick on and off? I have read like 20+ messages and they say different temperatures I have a 1990 IROC-Z 5.7 Auto, it has dual electric fans, and the serpentine system setup.

-Thanks

 

The following information was found in the FAQ from this website. Can anyone confirm this? Does anyone know what temperatures the fans should kick off?

"According to the 1990 service manual, the primary fan is controlled by the ECM and will come on when the coolant temperature reaches 190 degrees F. The secondary fan has its own temperature sensor in the bottom of the engine block (passenger side) and will turn on when both of these conditions exist:

* The coolant temperature is greater than 222 degrees F
* When the A/C control head pressure is greater than 1600kPa and the vehicle speed is less than 40 mph.

The Auxiliary Coolant Fan is controlled by the A/C Pressure switch and the auxiliary coolant fan switch. It is not controlled by the ECM. It should have black and black/pink wires going to it, and the coolant fan will have black and black/red wires going to it."

-Thanks

 

If that's what the manual says then go with it, mine (1989) says that the AUX cuts on at 243F. But it could very well be different for 1990. Is this a GM serive manual?
Also both are controlled by the ECM in the end, but get readings from their own sensors.

 

I have no idea what manual they are talking about... That info came from the FAQ on this website. It says that the AUX fan is NOT controlled by the ECM?!