A/c System Diagnosis - Manual Ford Bronco II I

Fixed Orifice Tube Cycling Clutch System Evaluation. Scheme 10

Flow Chart - Insufficient A/C Cooling. Scheme 11

Verify The Condition (1 of 2). Scheme 12

Verify The Condition (2 of 2). Scheme 13

A/C CLUTCH CIRCUIT ELECTRICAL DIAGNOSIS (CAPRI, CONTINENTAL, COUGAR, ESCORT, EXP, LYNX, MUSTANG & THUNDERBIRD ONLY)

An inoperative A/C compressor clutch may be caused by a diode connected in parallel to clutch field coil. If diode is shorted, symptoms will be the same as a shorted field coil (blown fuse). To prevent unnecessary replacement of clutch field coil, use the following test procedure

1. Disconnect wiring harness connector from A/C clutch field coil assembly. Using an ohmmeter, set at a low resistance range and connect test leads across 2 prongs in field coil connector. Ohmmeter should read approximately 2.5 to 4.5 range. If ohmmeter reads less than specified range and indicates a short condition, field coil must be replaced.
2. If resistance falls within specified range and short condition still exists when wiring harness connector is reconnected, diode and diode wiring harness should be tested for a short condition. Using an ohmmeter, set at a high resistance range and connect test leads across terminals of wire connector.
3. If resistance falls to zero, reverse leads at connector. If resistance reads in excess of 100,000 ohms, diode is good. If resistance is zero, diode is shorted and must be replaced.

DESCRIPTION

All electrically-driven fans are actuated by thermal relay switches. Thermal switches turn fan motor on when necessary and shut fan motor off when not needed. All air conditioned vehicles are equipped with over-ride switches. These switches turn fan motor on whenever air conditioning system is operating, and return fan motor control to thermal relay when system is turned off.

Although all electric fans operate on same principle, the following are special descriptions that apply to specific models

Coolant temperature switch activates coolant relay to provide battery power to fan motor when engine temperature reaches 221°F (105°C); relay shuts fan off when temperature drops sufficiently. After vehicle operation or when carburetor temperature exceeds 155°F (68°C), carburetor temperature relay switch activates timer relay. Timer relay turns fan on for a period of 15 minutes or until temperature drops to 155°F (68°C) or less.

Note. Timer relay works only when ignition switch is turned off. Avoid working around fan with ignition off when temperature at carburetor may exceed 155°F (68°C).

ENGINE COOLING FAN CIRCUIT ELECTRICAL DIAGNOSIS

If fan is not operating properly, disconnect fan motor wire connector and connect it with 14 gauge wire to a good 12-volt battery. If fan runs, motor is all right, indicating car battery, coolant relay, timer relay, or A/C relay may be defective. If fan motor does not run when connected directly to a good battery, replace fan motor.

Thermostatically Controlled Electric Fan. Scheme 14

FOT System Diagnosis (Capri, Continental, Cougar, Escort, EXP, LTD, Lynx, Mark VII, Marquis, Mustang, Tempo, Thunderbird & Topaz). Scheme 15

FOT System Diagnosis (Bronco, Bronco II, Crown Victoria, E" Series, "F" Series, Grand Marquis, Ranger & Town Car). Scheme 16

Flow Chart (1 of 2) - Excessive Compressor Vibration or Noise. Scheme 17

Flow Chart (2 of 2) - Excessive Compressor Vibration or Noise. Scheme 18

(1 of 2). Scheme 19

(2 of 2). Scheme 20

Note. Some noise and vibration is normal in all air conditioning systems. High temperatures and progressively increased system pressures will increase the noise and vibration level. This is a normal condition. Comparison and experience with air conditioning systems under various operating conditions will tell the technician which systems are not conforming to the normal pumping sound and vibration patterns made by a properly functioning compressor.

Compressor Clutch Diagnostic Charts (A1-A3). Scheme 21

Compressor Clutch Diagnostic Charts (A4-A6). Scheme 22

Compressor Clutch Diagnostic Charts (A7-A8). Scheme 23

Compressor Clutch Diagnostic Charts (A9-A11). Scheme 24

Compressor Clutch Diagnostic Charts (A1-A3). Scheme 25

Compressor Clutch Diagnostic Charts (A4-A6). Scheme 26

Compressor Clutch Diagnostic Charts (A7-A9). Scheme 27

Compressor Clutch Diagnostic Charts (A10-A12). Scheme 28

Compressor Clutch Diagnostic Charts (A13). Scheme 29

CONDITIONS & POSSIBLE CAUSES

A/C CLUTCH INOPERATIVE (CAPRI, CONTINENTAL, COUGAR, ESCORT, EXP, LYNX, MUSTANG & THUNDERBIRD ONLY)

An inoperative A/C compressor clutch may caused by a diode connected in parallel to clutch field coil. If diode is shorted, symptoms will be the same as shorted field coil (blown fuse). To prevent unnecessary replacement of clutch field coil, use the following test procedure

1. Disconnect wiring harness connector from A/C clutch field coil assembly. Using an ohmmeter, set at a low resistance range and connect test leads across 2 prongs in field coil connector. Ohmmeter should approximately read 2.5 to 4.5 range. If ohmmeter reads less than specified range and indicates a short condition, field coil must be replaced.
2. If resistance falls within specified range and short condition still exists when wiring harness connector is reconnected, diode and diode wiring harness should be tested for a short condition. Using an ohmmeter, set at a high resistance range and connect test leads across terminals of wire connector.
3. If resistance falls to zero, reverse leads at connector. If resistance reads in excess of 100,000 ohms, diode is good. If resistance still indicates zero, diode is shorted and must be replaced.