1995 Radiator Fan operation

[scudballs]

For those of you wondering when your radiator fans are suppose to turn on. This is the fan operation for a 1995.

The electric cooling fan(s) are used to cool engine coolant flowing through the radiator. They are also used to cool the refrigerant (R134a) flowing through the A/C condenser.

OPERATION
The electric cooling fans are controlled by the PCM. The PCM controls the ground path for the three cooling fan relays. The relays are used to control the high current flow to power the cooling fan motors. Both fans operate together. When minimum cooling is required, the PCM energizes the low speed cooling fan relay #1, and both fans operate at low speed since the fans are connected in series through the series/parallel cooling fan relay #2. When maximum cooling is required, the PCM energizes all three cooling fan relays. The left hand coolant fan is still power through the low speed cooling fan relay #1, but is now grounded through the series/parallel cooling fan relay #2 and operates at high speed. The right hand coolant fan is powered directly through the high speed cooling fan relay #3 and also operates at high speed.

Low Speed Fans
The cooling fans are controlled by the PCM based on inputs from the A/C system, Engine Coolant Temperature (ECT) sensor and Vehicle Speed Sensor (VSS) .

The PCM will command low speed fans "ON" when Engine Coolant Temperature (ECT) is above 106°C (223°F). The PCM will turn the fans "OFF" when the temperature drops about 3°C (5°F). The minimum "ON" time for low speed fans is 50 seconds.

High Speed Fans
The PCM will command high speed fans "ON" when any of the following conditions exist at idle.



Certain Diagnostic Trouble Codes (DTCs) set.
ECT above 110°C (230°F).
A/C head pressure above 248 psi.
If the high speed fans were turned "ON" by the ECT, the PCM will switch the fans back to low speed when the temperature drops about 3°C (5°F). Minimum "ON" time for HI speed fans is 30 seconds.

[kiway22]

I was reading about the fans in my '97 manual. And it says both fans will come on at a set temperature. And run at low speed. But when there is a demand for more cooling, only the left fan will run at high speed until the demand has been met.