Air Conditioning Operation - Toyota Camry 1999 Electrical Troubleshooting Manual

AIR CONDITIONING (AUTOMATIC A/C)

5. AIR CONDITIONING OPERATION

The A/C control assembly receives various signals, I.E., the engine RPM from the engine control module, out side air
temperature signal from the A/C ambient temp. sensor, coolant temperature from the engine control module and the lock
signal from the A/C compressor, etc.
When the engine is started and the A/C SW (A/C control assembly) is on, a signal is input to the A/C control assembly.
As a result, the ground circuit in A/C control assembly is closed and current flows from HEATER fuse to TERMINAL 1 of
the MG CLT relay to TERMINAL 2 to TERMINAL 3 of the diode (A/C) to TERMINAL 2 to TERMINAL MGCR of the A/C
control assembly to TERMINAL GND to GROUND, turning the MG CLT relay on, so that the magnetic clutch is on and the
A/C compressor operates.
At the same time, the engine control module. Detects the magnetic clutch is on and the A/C compressor operates.
If the A/C control assembly detects the following conditions, it stops the air conditioning:
∗ Evaporator outlet air is too low.
∗ There is a marked difference between the compressor speed and the engine speed.
∗ The refrigerant pressure is abnormally high or abnormally low.
∗ The engine speed is too low.
∗ Rapid acceleration occurs.
SERVICE HINTS
A3 A/C DUAL PRESSURE SW
4–1 : Open above approx. 2.0 kgf/cm
A2 A/C MAGNETIC CLUTCH AND LOCK SENSOR
4–GROUND : Approx. 3.7 Ω
A34 (A), A35 (B) A/C CONTROL ASSEMBLY
B–GROUND : Always approx. 12 volts
IG+ –GROUND : Approx. 12 volts with the ignition SW at ON position
HR –GROUND : Approx. 12 volts with the ignition SW at ON position and do not turn the blower motor
Below 1 volts with the ignition SW at ON position and turn the blower motor
PSW–GROUND : Below 1 volts with the ignition SW at ON position
AC1–GROUND : Below 1 volts at start the engine, operate the compressor
+ OR MORE volts at start the engine, do not operate the compressor
BLW–GROUND : Below 1.5 volts with the ignition SW on and turn the blower motor
S5–SG : 4–6 volts with the ignition SW at ON position
SG–GROUND : Always continuity
AMH–AMC : 1.3–1.9 volts with the ignition SW off
AIF–GROUND : Approx. 12 volts with the FRESH SW on
AIR–GROUND : Approx. 12 volts with the RECIRC SW on
FACE–GROUND: Approx. 12 volts with the FACE SW on
DEF–GROUND : Approx. 12 volts with the DEF SW on
GND–GROUND : Always continuity
: PARTS LOCATION
Code See Page
A2 26 (1MZ–FE)
A3 26 (1MZ–FE)
A13 30
A20 30
A30 26 (1MZ–FE)
A33 30
A34 A 30
A35 B 30
: RELAY BLOCKS
Code See Page
1 24
2
(29 psi, 196 kpa) or 32 kgf/cm
Code
A36
A37
A38
A39
B3
B8
D3
E8
Relay Blocks (Relay Block Location)
Engine Room R/B No.1 (Engine Compartment Left)
2
(464 psi, 3138 kpa)
See Page
30
30
30
30
30
30
30
30
Code See Page
F8 26 (1MZ–FE)
J1 31
J11 31
J27 A 31
J28 B 31
J29 31
J32 31