2004 ISUZU TF SERIES relay

HEATER AND AIR CONDITIONING 1-87

MAGNETIC CLUTCH
When the A/C switch and the fan control knob (fan switch) are turned on with the engine running, current flows
through the thermostat and the compressor relay to activate the magnetic clutch.
The air conditioning can be stopped by turning off the A/C switch or the fan control knob (fan switch).
However, even when the air conditioning is in operation, the electronic thermostat, the pressure switch or the ECM
is used to stop the air conditioning temporarily by turning off the magnetic clutch in the prearranged conditions to
reduce the engine load which is being caused by the rise in the engine coolant temperature, and the acceleration of
the vehicle, etc.

1-90 HEATER AND AIR CONDITIONING

MAGNETIC CLUTCH DOES NOT RUN (4JA1L/4JH1-TC)



Replace
YES


Are the A/C thermo (X-15) and heater & A/C (X-11)
and A/C compressor (X-14) relay OK?

Are the No. SBF-8 fuse (30A) and the No. EB-13
(10A) fuses OK
YES


Is the pressure switch (C-24) OK?
YES


Are the A/C switch (B-57) and the fan switch (B-13)
OK?
NO
YES


Is there continuity between the engine harness
connector terminal No.1 (E-3) and engine room harness
connector terminal No.2 (X-14)?

Disconnect the A/C compressor relay.

Turn the ignition switch "ON" (Engine is running)


A/C switch and fan control knob (fan switch "ON")
NO
Replace
NO
Defective switch or insufficient
refrigerant
NO
NO
Does the magnetic clutch
operate?
YES
Replace


Disconnect the magnetic clutch connector.

Is there battery voltage between the engine room harness
connector terminal No.1 (E-3) and ground?
Defective compressor
YESNO
Defective magnetic clutch

HEATER AND AIR CONDITIONING 1-91





Open circuit between the engine
harness connector terminal No.1 (E-3)
and engine room harness connector
terminal No.2 (X-14).
YES


Is there battery voltage between the engine room
harness connector terminal No.1 (X-14) and
ground?
YES


Disconnect the A/C thermo relay.
YES


Is there continuity between the ECM harness
connector terminal No.38 (C-56) and engine
room harness connector terminal No.4 (X-14)?
NO
Open circuit between the No. EB-13
fuse and engine room harness
connector terminal No.1 (X-14).
NO
Open circuit between the engine room
harness connector terminal No.1 (X-
15) and engine room harness
connector terminal No. 3 (X-14).
NO

Is there continuity between the engine room
harness connector terminal No.3 (X-14) and No.1
(X-15)?
YES


Is there continuity between the ECM harness
connector terminal No.30 (C-56) and engine
room harness connector terminal No.2 (X-15)? Open circuit between the engine room
harness connector terminal No.1 (X-
15) and engine room harness
connector terminal No. 3 (X-14).
NO
YES


Is there battery voltage between the engine room
harness connector terminal No.4 (X-15) and
ground?
Open circuit between the ECM
harness connector No. 38 (C-56) and
engine room harness connector
terminal No. 4 (X-14).
NO
YES


Is there continuity between the engine room
harness connector terminal No. 3 (X-15) and the
engine room harness connector terminal No. 1 (C-
24).
Open circuit between the No. EB-13
fuse and engine room harness
connector terminal No. 4 (X-15).
NO


Disconnect the ECM harness connector.


Disconnect the pressure switch?

1-92 HEATER AND AIR CONDITIONING




YES

Disconnect the condenser fan relay connector
condenser fan.
YES


Is there battery voltage between the engine
room harness connector terminal NO.3 (C-
24) and ground? Open circuit between the condenser
fan relay 4JH1TC No.4 (X-6) 4JA1L
No. 3 (X-13) and engine room harness
connector terminal No. 4 (X-14).
NO

Is there continuity between the relay terminal
4JH1TC No. 4 (X-6) 4JA1L No.3 (X-13)and
engine room harness connector terminal No.4
(C-24)?
YES


connect the A/C thermo relay connector.
Open circuit between the No. EB-13
fuse and engine room harness
connector terminal No. 3 (C-24).
NO
YES


Is there battery voltage between the engine
room harness connector terminal No.3 (C-55)
dd?
Open circuit between the engine room
harness connector terminal No. 2 (C-
55) and the engine room harness
connector terminal No. 2 (C-24).
NO
YES


Is there continuity between the engine room
harness connector terminal No.1 (C-55) and
ground (C-109) ? or (cooler only) the short
connector terminal No.3 (B-79) and ground (C-
109
)?
Open circuit between the No. EB-13
fuse and engine room harness
connector terminal No. 3 (C-55).
NO


Disconnect the electronic themostat.


Is there continuity between the engine room
harness connector terminal No. 2 (C-55) and the
engine room harness connector terminal No. 2
(C-24).
Open circuit between and engine room
harness connector terminal No. 3 (X-
15) and the engine room harness
connector terminal No. 1(C-24).
NO

HEATER AND AIR CONDITIONING 1-95

MAGNETIC CLUTCH DOES NOT RUN


Replace
YES

Are the A/C thermo (X-15), heater & A/C (X-11)
and A/C compressor (X-14) relay OK?


Are the No. SBF 8 fuse (30A) and the No. EB-13
(10A) fuses OK
YES

Is the pressure switch (C-24) OK?
YES


Are the A/C switch (B-57) and the fan switch (B-13)
OK?
NO
YES


Is there continuity between the engine harness
connector terminal No.1 (E-2) and engine room
harness connector terminal No.2 (X-14)?


Disconnect the A/C compressor relay.


Turn the ignition switch "ON" (Engine is running)

A/C switch and fan control knob (fan switch "ON")
NO
Replace
NO
Defective switch or insufficient
refrigerant
NO
NO
Does the magnetic clutch
operate?
YES
Replace


Disconnect the magnetic clutch connector.


Is there battery voltage between the engine room
harness connector terminal No.1 (E-2) and ground?
Defective compressor
YESNO
Defective magnetic clutch

1-96 HEATER AND AIR CONDITIONING




Open circuit between the engine
harness connector terminal No.1 (E-
13) and engine room harness
connector terminal No.2 (X-14).
YES


Is there battery voltage between the engine room
harness connector terminal No.1 (X-14) and
ground?
YES


Disconnect the A/C thermo relay.
YES

Is there continuity between the ECM harness
connector terminal No. 11 (E-61) and engine
room harness connector terminal No.4 (X-14)?
NO
Open circuit between the No. EB-13
fuse and engine room harness
connector terminal No.1 (X-14).
NO
Open circuit between the No.EB-13
fuse and engine room harness
connector terminal No. 3 (X-14).
NO

Is there battery voltage the engine room harness
connector terminal No.3 (X-14) and ground?
YES


Is there continuity between the ECM harness
connector terminal No.31 (E-61) and engine
room harness connector terminal No.1 (X-15)? Open circuit between the ECM
harness connector No. 11 (E-61) and
engine room harness connector
terminal No. 4 (X-14).
NO
YES

Is there battery voltage between the engine room
harness connector terminal No.3 (X-15) and
ground?
Open circuit between the No. EB-13
fuse and engine room harness
connector terminal No. 2 (X-15).
NO
YES

Is there continuity between the engine room harness
connector terminal No. 4 (X-15) and the engine room
harness connector terminal No. 1 (C-24)?
Open circuit between the No. EB-13
fuse and engine room harness
connector terminal No. 3 (X-15).
NO


Disconnect the ECM harness connector.

Disconnect the pressure switch.

HEATER AND AIR CONDITIONING 1-97



YES

Disconnect the condenser fan relay connector
condenser fan.
YES


Is there battery voltage between the engine
room harness connector terminal NO. 3 (C-
24) and ground? Open circuit between the condenser
fan relay No.4 (X-6) 4JAH No. 3 (X-
13) and engine room harness
connector terminal No. 4 (X-14).
NO

Is there continuity between the relay terminal
No. 4 (X-6) and engine room harness connector
terminal No.4 (C-24)?
YES

connect the A/C thermo relay connector.
Open circuit between the No. EB-13
fuse and engine room harness
connector terminal No. 4 (C-24).
NO
YES

Is there battery voltage between the engine
room harness connector terminal No.3 (C-55)
dd?
Open circuit between the engine room
harness connector terminal No. 2 (C-
24) and the engine room harness
connector terminal No. 2 (C-55).
NO
YES

Is there continuity between the engine room
harness connector terminal No.1 (C-55) and
ground (C-109) ? Open circuit between the No. EB-13
fuse and engine room harness
connector terminal No. 3 (C-55).
NO


Disconnect the electronic themostat.


Is there continuity between the engine room
harness connector terminal No. 2 (C-55) and the
engine room harness connector terminal No. 2
(C-24)?
Open circuit between the engine
room harness connector terminal
No. 4 (X-15) and the engine room
harness connector terminal No. 1(C-
24).
NO

1-100 HEATER AND AIR CONDITIONING



Replace
YES


Are the A/C thermo (X-15), heater & A/C (X-11)
and A/C compressor (X-14) relay OK?


Are the No. SBF 8 fuse (30A) and the No. EB-13
(10A) fuses OK?
YES


Is the pressure switch (C-24) OK?
YES


Are the A/C switch (B-57) and the fan switch (B-13)
OK?
NO
YES


Is there continuity between the engine harness
connector terminal No.1 (E-2) and engine room
harness connector terminal No.2 (X-14)?

Disconnect the A/C compressor relay.


Turn the ignition switch "ON" (Engine is running)


A/C switch and fan control knob (fan switch "ON")
NO
Replace
NO
Defective switch or insufficient
refrigerant
NO
NO
Does the magnetic clutch
operate?
YES
Replace


Disconnect the magnetic clutch connector.

Is there battery voltage between the engine room
harness connector terminal No.1 (E-2) and ground?
Defective compressor
YESNO
Defective magnetic clutch