LS 400 V8-4.0L (1UZ-FE) (1990)
Radiator Cooling Fan Motor: Description and Operation
Circuit Operation
Cooling Fan Operation
When the ignition sw is turned on:
-
the current from ign fuse flows to terminal 3 of Cooling Fan Relay No.3
-->
terminal 1
-->
terminal 1 of Water Temp. Switch (for cooling fan)
-->
terminal 2
-->
ground, from terminal 1 of Cooling Fan Relay No.2
-->
terminal 2
-->
terminal 1 of Water Temp. Switch (for Cooling Fan)
-->
terminal 2
-->
ground, and also from terminal 1 of Cooling Fan Relay No.1
-->
terminal 2
-->
terminal 2 of A/C Pressure Switch (high pressure)
-->
terminal 3
-->
ground. causing Cooling Fan Relays No.1. 2 and 3 to turn on.
At that time, the current from FL RDI fan flows to termimal 3 of Cooling Fan Relay No.2 and terminal 1 of Cooling Fan Motor No.1
-->
terminal 2
-->
termimal 4 of Cooling Fan Relay No.3
-->
terminal 5
-->
terminal 3 of Cooling Fan Relay No.1
Operation At Low Speed
During a/c operation, when the pressure of a/c compressor becomes higher (more than 14.3 kg/square cm, 1401 KPa, 203 Psi) than normal pressure,
the A/C High Pressure Switch turns off.
-
As a result, Cooling Fan Relay No.1 turns off and the current flows from FL RDI fan:
-->
terminal 1 of Cooling Fan Motor No.1
-->
terminal 2
-->
terminal 4 of Cooling Fan Relay No.3
-->
terminal 5
-->
terminal 3 of Cooling Fan Relay No.1
-->
terminal 4
-->
terminal 1 of Cooling Fan Motor No.2
-->
terminal 2
-->
ground, flowing to the fan motor in series, causing the cooling fan to rotate at low speed.
Operation At High Speed
When the engine coolant temperature becomes more than about 90° C (194° F) the water temp. switch turns off.
-
As a result, Cooling Fan Relays No.2 and No.3 turn off, and current flows from FL RDI fan to terminal 1 of Cooling Fan Motor No.1
-->
termimal 2
-->
terminal 4 of Cooling Fan Relay No.3
-->
terminal 2
-->
ground. At the same time, current flows from FL RDI fan to termimal 3 of Cooling Fan Relay No.2
-->
terminal 4
-->
terminal 1 of Cooling Fan Motor No.2
-->
terminal 2
-->
ground, the current flowing to the fan motor in parallel causing the cooling fan to rotate at high speed.