1991 LEXUS SC400 Service Repair Manual

Page 113 of 4087

LEXUS SC400 1991  Service Repair Manual 
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Back±up Power Source Circuit
CIRCUIT DESCRIPTION
This is the backup power so

Page 114 of 4087

LEXUS SC400 1991  Service Repair Manual 
Check  voltage between terminals B of air conditioner control assembly
connector and body ground.
(1) Remove console upper panel.(See page BO-111 ).
(2) Remove A/C control assembly with connec±
tors

Page 115 of 4087

LEXUS SC400 1991  Service Repair Manual 
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Heater Main Relay Circuit
CIRCUIT DESCRIPTION
The heater main relay is switch

Page 116 of 4087

LEXUS SC400 1991  Service Repair Manual 
Check  voltage between terminals HR of air conditioner control assem-
bly  connector and body ground.
(1) Remove console upper panel.(See page BO-111 ).
(2) Remove A/C control assembly with connec±

Page 117 of 4087

LEXUS SC400 1991  Service Repair Manual 
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Power Transistor Circuit
CIRCUIT DESCRIPTION
The air conditioner control asse

Page 118 of 4087

LEXUS SC400 1991  Service Repair Manual 
Check power transistor.
(1) Remove  cooling unit (See page BO-107).
(2) Disconnect power transistor connector.
(1) Check test bulb lights up when battery and 
resistor are connected to power transist

Page 119 of 4087

LEXUS SC400 1991  Service Repair Manual 
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Blower Motor Circuit
CIRCUIT DESCRIPTION
This is the power source for the blo

Page 120 of 4087

LEXUS SC400 1991  Service Repair Manual 
 Check blower motor.
Remove blower motor.(See page AC-129).
Connect positive   lead connected to terminal 2 of
blower motor connector, negative   lead to 
terminal 1.
Blower motor operates smoothly