Ford Falcon. Manual - part 314

412-03-29 Air 

Conditioning 412-03-29

DIAGNOSIS AND TESTING (Continued)

C-127 (A/C Clutch Diode)

Pin Number(s)

Circuit Designation/Description

Normal Condition/Measurement

1

Circuit 57S B

Earth (less then 5 Ohms to chassis ground)

Ground

2

Circuit 347B B-Y

12V when A/C on

Power

C-122(A/C Pressure Transducer)

Pin Number(s)

Circuit Designation/Description

Normal Condition/Measurement

1

Circuit 359C GR

Earth (less then 5 Ohms to chassis ground)

2

Circuit 440 BR

Feedback Voltage 0V to 5.0V

3

Circuit 351E BR-W

Reference Voltage 5.0V

±0.25V

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412-03-30 Air 

Conditioning 412-03-30

DIAGNOSIS AND TESTING (Continued)

C163 (Power Distribution Board) - WAC Relay

Pin Number(s)

Circuit Designation/Description

Normal Condition/Measurement

1

Circuit 347B B-Y

12V supplied when Relay engaged

Power

2

Circuit 175A B-Y

12V supplied with IG ON condition

3

Circuit 321 GR-W

Earth from ECC for A/C operation

4

Circuit 361C R

12V supplied with A/C Relay engaged

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412-03-31 Air 

Conditioning 412-03-31

DIAGNOSIS AND TESTING (Continued)

C-376 Evaporator Thermister
NOTE: View from wire entry side (rear).

Pin Number(s)

Circuit Designation/Description

Normal Condition/Measurement

1

Sensor ground

Voltage (V) between HIM terminal connection D

pin 1 and C376 pin 13

0V (ground)

2

Sensor supply

Voltage (V) between HIM terminal connection D

pin 2 and C376 pin 13
NOTE: With ignition ON and sensor

disconnected, refer to sensor voltage from

sensor output table, Pinpoint test G.

Air Conditioning & HVAC Relay and

Fuses

The air conditioning compressor cut-out relay (WAC relay, R3-black) is located in the Engine Compartment

Fuse Box.
The A/C compressor clutch is protected with a 30 amp fuse (F11-pink, combined with the engine fuse) located

in the Engine Compartment Fuse Box.
The A/C condenser fans (engine cooling fans) are controlled with three relays (R8, R9, R10-all white) located

in the Engine Compartment Fuse Box. Each fan circuit is protected with a 40 amp fuse (F5, F6-both green)

also located in this fuse box.
The three relay coils are protected by a single 15A fuse (F2-blue) located in the instrument panel fuse box.
The HIM electrical circuits are protected with two fuses, one 15 amp (F4-blue) and one 10 amp, (F27-red),

both located in the Instrument Panel Fuse Box.
The HVAC blower fan circuit is protected with a 40 amp fuse (F7-green) located in the Engine Compartment

Fuse Box.

Pinpoint Tests

Special Tool(s)

Electrical Multimeter

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412-03-32 Air 

Conditioning 412-03-32

DIAGNOSIS AND TESTING (Continued)

PINPOINT TEST A : COMPRESSOR OPERATION

Test Step

Result / Action to Take

A1

CHECK COMPRESSOR OPERATION

Turn blower motor to high speed

Yes

Operation is normal.

Turn A/C switch on.

No

Set controls to maximum cooling.

Go to A2.

Inspect magnetic clutch operation.

Does rotor and hub engage and drive the compressor?

A2

CHECK THE A/C COMPRESSOR CIRCUIT 347 (B-Y) FOR

POWER

Measure the voltage between the A/C compressor clutch C-121,

Yes

circuit 347A, harness side and ground.

Go to A3.

Is the voltage greater than 10 volts?

No

Go to A4.

A3

CHECK THE A/C COMPRESSOR CIRCUIT 57 (B) FOR

OPEN CIRCUIT

Measure the resistance between the A/C compressor clutch, circuit

Yes

57A (B) harness side and ground.

INSTALL a new compressor. Refer to Section
412-03.

Is the resistance less than 5 ohms?

No

REPAIR the circuit. TEST the system for normal
operation.

A4

CHECK CIRCUIT 347 (B-Y) FOR POWER

Measure the voltage between the A/C clutch relay circuit 347, harness

Yes

side and ground.

Repair circuit, Test for normal operation from
relay to compressor.

Is the voltage greater than 10 volts?

No

Go to A5.

A5

CHECK THE A/C CLUTCH RELAY CIRCUIT 175 (B-Y)

FOR POWER

Measure the voltage between A/C clutch relay C163, circuit 175A

Yes

(B-Y), harness side and ground.

Go to B1. Check relay operation.

Is the voltage greater than 10 volts?

No

Go to A6.

A6

CHECK THE 30A FUSE C163 CIRCUIT 50 (R) FOR

POWER

Measure the voltage between fuse pin and ground.

Yes

Repair the circuit from the fuse to relay.

Is the voltage greater than 10 volts?

Test the system for normal operation.

No

Inspect battery and wiring circuit. Repair the
circuit, test the system for normal operation.

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