Toyota 1993 MR2 Wiring Diagrams page 174

RADIATOR FAN AND AIR CONDITIONER
SYSTEM OUTLINE
1. COOLING FAN OPERATION
WHEN THE IGNITION SW IS TURNED ON, THE CURRENT FROM AM2 FUSE FLOWS TO TERMINAL 1 OF FAN MAIN RELAY
TERMINAL 3 GROUND, CAUSING THE FAN MAIN RELAY OF EACH FAN TO TURN ON.
AT THAT TIME, THE CURRENT FROM AM2 FUSE FLOWS TO FAN RELAY NO. 1 AND NO. 2, AND FLOWS FROM TERMINAL 2 OF FAN
RELAY NO. 1 AND NO. 2
AMPLIFIER. AT THE SAME TIME, THE CURRENT FROM GAUGE FUSE FLOWS TO TERMINAL 7 OF A/C AMPLIFIER
TERMINAL 1 OF FAN RELAY NO. 3
* OPERATION AT LOW SPEED
WHEN THE IGNITION SW IS TURNED ON, THE FAN MAIN RELAY AND FAN RELAY NO. 1, NO. 2 AND NO. 3 TURN ON, THE CURRENT
FLOWS FROM ALT FUSE FLOWS TO TERMINAL 5 OF FAN MAIN RELAY
CONDENSER FAN MOTOR
TERMINAL 3 TERMINAL 2 OF RADIATOR FAN MOTOR
CAUSING THE FAN TO ROTATE AT LOW SPEED.
* OPERATION AT HIGH SPEED
DURING A/C OPERATION, WHEN THE PRESSURE OF A/C COMPRESSOR BECOMES HIGHER THAN NORMAL PRESSURE (MORE
THAN 1402 KPA 14.3 KG/CM
AS A RESULT, FAN RELAY NO. 1 AND NO. 2 TURNS OFF AND THE CURRENT FLOWS FROM ALT FUSE TO TERMINAL 5 OF FAN MAIN
RELAY TERMINAL 4
RELAY NO. 2 TERMINAL 4
TERMINAL 4 OF FAN RELAY NO. 1
TO EACH FAN MOTOR IN PARALLEL CAUSING THE FAN TO ROTATE AT HIGH SPEED.
NOTE THAT, EVEN IF THE ENGINE COOLANT TEMPERATURE RISES ABOVE 90°C (194°F), THE WATER TEMP. SW (FOR RADIATOR
FAN) TURNS OFF A SIGNAL IS SENT TO TERMINAL 9 OF A/C AMPLIFIER. BECAUSE CURRENT FLOW FROM TERMINAL 8 OF A/C
AMPLIFIER TO TERMINAL 6 IS SHUT OFF, THE CIRCUIT BETWEEN THE A/C SINGLE PRESSURE SW AND GROUND IS DEACTIVATED,
SO THE SAME OPERATION CONTINUES.
2. HEATER BLOWER MOTOR OPERATION
CURRENT IS APPLIED AT ALL TIMES THROUGH THE HTR FUSE TO TERMINAL 5 OF HEATER RELAY.
WHEN THE IGNITION SW IS TURNED TO ON, CURRENT FLOWS THROUGH GAUGE FUSE TO TERMINAL 1 OF HEATER RELAY
TERMINAL 3 TERMINAL 10 OF AIR VENT MODE CONTROL SERVO MOTOR
CONTROL ASSEMBLY.
* LOW SPEED OPERATION
WHEN THE BLOWER SW (A/C CONTROL ASSEMBLY) IS MOVED TO LOW POSITION, THE CURRENT FLOWS TO TERMINAL (A) 4 AND
(A) 5 OF A/C CONTROL ASSEMBLY
ON.
THIS CAUSES THE CURRENT FLOWING FROM THE HTR FUSE TO TERMINAL 5 OF THE HEATER RELAY TO FLOW TO TERMINAL 4 OF
HEATER RELAY TERMINAL 1 OF BLOWER MOTOR
GROUND, CAUSING THE BLOWER MOTOR TO ROTATE AT LOW SPEED.
* HIGH SPEED OPERATION
WHEN THE BLOWER SW (A/C CONTROL ASSEMBLY) IS MOVED TO HI POSITION, THE CURRENT FLOWS TO TERMINAL (A) 4 AND (A)
5 OF A/C CONTROL ASSEMBLY
THIS CAUSES THE CURRENT FLOWING FROM THE HTR FUSE TO TERMINAL 5 OF THE HEATER RELAY TO FLOW TO TERMINAL 4 OF
HEATER RELAY TERMINAL 1 OF BLOWER MOTOR
(A) 6 GROUND, CAUSING THE BLOWER MOTOR TO ROTATE AT HIGH SPEED.
* MIDIUM SPEED OPERATION (OPERATION AT M1, M2)
WHEN THE BLOWER SW (A/C CONTROL ASSEMBLY) IS MOVED TO M1 POSITION, THE CURRENT FLOWS TO TERMINAL (A) 4 AND (A)
5 OF A/C CONTROL ASSEMBLY
THIS CAUSES THE CURRENT FLOWING FROM THE HTR FUSE TO TERMINAL 5 OF THE HEATER RELAY TO FLOW TO TERMINAL 4 OF
HEATER RELAY TERMINAL 1 OF BLOWER MOTOR
TERMINAL (A) 1 OF A/C CONTROL ASSEMBLY
MEDIUM LOW SPEED.
WHEN THE BLOWER SW (A/C CONTROL ASSEMBLY) IS MOVED TO M2 POSITION, CURRENT FLOWS FROM TERMINAL 5 OF HEATER
RELAY TERMINAL 1 OF BLOWER RESISTOR
TERMINAL (A) 6 GROUND.
THIS CURRENT FLOW FROM BLOWER MOTOR TO GROUND IS GREATER THAN AT M1 POSITION, SO THE BLOWER MOTOR ROTATES
AT MEDIUM HIGH SPEED.
182
TERMINAL 1 TERMINAL 2 OF A/C HIGH SINGLE PRESSURE SW
TERMINAL 2 GROUND, CAUSING THE FAN RELAY NO. 3 TO TURN ON.
TERMINAL 1 TERMINAL 3 OF FAN RELAY NO. 2
2
203 PSI), THE A/C SINGLE PRESSURE SW TURNS OFF.
CDS FAN FUSE TERMINAL 2 OF A/C CONDENSER FAN MOTOR
GROUND, AT THE SAME TIME FROM TERMINAL 4 OF FAN MAIN RELAY TO RDI FAN FUSE
TERMINAL 3 TERMINAL 2 OF RADIATOR FAN MOTOR
TERMINAL (A) 6 OF A/C CONTROL ASSEMBLY
TERMINAL (A) 6 OF A/C CONTROL ASSEMBLY
TERMINAL (A) 6 OF A/C CONTROL ASSEMBLY
TERMINAL (A) 6
TERMINAL 3
TERMINAL 4
TERMINAL 5
TERMINAL 1 GROUND, FLOWING TO EACH FAN MOTOR IN SERIES,
TERMINAL 11
TERMINAL 2 TERMINAL 1 OF BLOWER RESISTOR
GROUND AND TURNS THE HEATER RELAY ON.
TERMINAL 2 TERMINAL (A) 3 OF A/C CONTROL ASSEMBLY
GROUND AND TURNS THE HEATER RELAY ON.
TERMINAL 2 TERMINAL 1 OF BLOWER RESISTOR
GROUND, CAUSING THE BLOWER MOTOR TO ROTATE AT
TERMINAL (A) 2 OF BLOWER SW (A/C CONTROL ASSEMBLY)
TERMINAL 1 TERMINAL 8 OF A/C
CDS FAN FUSE TERMINAL 2 OF A/C
TERMINAL 5 OF FAN RELAY NO. 3
TERMINAL 1 TERMINAL 3 OF FAN
TERMINAL 1 GROUND, FLOWING
TERMINAL (A) 4 AND (A) 5 OF A/C
GROUND AND TURNES THE HEATER RELAY
TERMINAL 1
TERMINAL 4
TERMINAL
TERMINAL 2