Suspension - Automatic Level Control Ford LTD Crown Victoria I

DESCRIPTION

The automatic leveling system is an air-operated, computer-controlled leveling system. Components are in addition to the standard rear suspension. Vehicle trim height (ride height) automatically adjusts to varying loads, with the aid of air shocks. The system consists of air-adjustable shocks, a compressor assembly, air drier with minimum retention valve, exhaust solenoid, compressor relay, rotary height sensor, microcomputer module, wiring and nylon tubing.

OPERATION

Air suspension leveling system operates by adding or removing air in the air shocks to maintain level of vehicle at a predetermined rear suspension height. The suspension height is controlled by a rotary height sensor. Airflow to the entire system is controlled by the interaction of the air compressor, vent solenoid, height sensor and microcomputer module.

AIR COMPRESSOR

A single cylinder piston-type air compressor is mounted on the left front wheelwell of all models. The compressor is electrically operated. A regenerative-type drier is attached to compressor manifold. All airflow during compression or venting passes through the drier. The vent solenoid, located on compressor manifold, controls air expulsion. A minimum retention valve, located inside the air drier, maintains a minimum pressure in air shocks of 10-22 psi.

MICROCOMPUTER MODULE

The microcomputer module is mounted behind the right rear trim panel in the luggage compartment. It controls the compressor relay and vent solenoid. The microcomputer module also controls power and ground to the rotary sensor. The module provides a 7-13 second time delay before any circuit can be completed.

The microcomputer module monitors air suspension system through inputs from the height sensor and ignition circuits. It limits compressor run time to 2 minutes and exhaust solenoid time to one minute. This function is to limit continuous compressor operation in case of a severe system leak or a malfunctioning exhaust valve. The timer function is reset when ignition key is cycled to the "OFF" and "RUN" positions.

ROTARY HEIGHT SENSOR

The air suspension leveling system operates by adding or removing air to maintain vehicle height. Trim height is controlled by the rotary height sensor. The sensor is located at the center of rear crossmember above the center section of the axle.

The sensor operates as follows: as weight is added to vehicle, the body will settle under load. As vehicle lowers, height sensor arm is rotated upward (low out-of-trim), sending 2 signals to microcomputer. After 7-13 seconds of continuous height sensor signal, the air compressor activates to send air to the shocks.

When pre-set trim height is reached, the air compressor shuts off. As weight is removed from the vehicle, the body will raise. As vehicle rises, the height sensor arm is rotated downward (high out-of-trim). After sending a continuous 7-13 second signal to microcomputer, the vent solenoid is activated and allows air to escape. As vehicle lowers, height sensor rotates upward. When pre-set trim height is reached, vent solenoid valves close.

Scheme 1

RIDING HEIGHT ADJUSTMENT

Raise and support vehicle. Loosen attaching nut at upper control arm. Move sensor attachment desired amount. There are 3 adjustment positions provided on the arm. One position change will provide.354" (9 mm) change. Lower vehicle and turn ignition on. Check ride height. (Scheme 2)

Scheme 2

SYSTEM OPERATION CHECK

Note. Always cycle ignition on and off before starting tests to ensure vent solenoid and compressor "on times" are reset.

1. Set vehicle ride height to specification. Briefly start and run engine. Apply a load of 300-350 lbs. (136-159 kg) to the rear of the vehicle. There should be a 7-13 second delay before the compressor turns on and rear of vehicle starts to rise.
2. Vehicle should rise to within 1/2" (13 mm) of ride height set in step 1) by the time the compressor shuts off. If vehicle does not rise to within 1/2" (13 mm) of the unloaded specification, check trunk for overloading. If overloaded, remove load and retest.
3. Remove load applied in step 1). There should be a 7-13 second delay before vehicle starts to lower. Vehicle should lower to within 1/2" (13 mm) of ride height specification. If not, refer to «DIAGNOSTIC TESTING»(/ford/ltd-crown-victoria/i-1983-1991/remont/electronic-suspension/#suspension-automatic-level-control__diagnostic-testing) in this article.

RESIDUAL PRESSURE CHECK

1. Remove the air line from the drier and attach it to one side of a pressure gauge. Connect the drier to the other side of the gauge using a short piece of nylon tubing. Cycle the ignition on and off.
2. Apply a load of 300-350 lbs. (136-159 kg) to the rear of vehicle to run the compressor and raise vehicle. Remove load and allow system to exhaust air pressure and lower vehicle.
3. When no more air is being exhausted, the gauge should read 8-24 psi. Remove pressure gauge and reconnect the system. Repeat steps 1) and 2) to ensure there is system air pressure in the shocks.

LEAK CHECK

1. Repeat steps 1) and 2) of «RESIDUAL PRESSURE CHECK»(/ford/ltd-crown-victoria/i-1983-1991/remont/electronic-suspension/#suspension-automatic-level-control__residual-pressure-check) . Allow the system to fill until the gauge reads 70-100 psi. With load still applied, disconnect wiring harness connector from the microcomputer module and then remove the load.
2. Rear of vehicle should rise. Cycle ignition on and off. Observe system for leaks for about 15 minutes. If system will not inflate to more than 50 psi, a severe air leak is indicated. Check air line between compressor and shocks for damage.
3. Check all connections with soap/water solution. If pressure is stable, perform diagnostic test. NOTE: If compressor is allowed to run until maximum output pressure is reached, the vent solenoid valve will function as a relief valve.The leak-down after compressor shut-down will indicate a false air leak.
4. Attach wire connector to module. Cycle ignition switch from "OFF" to "RUN" position. Allow air to exhaust and vehicle to lower. Remove pressure gauge from system and reconnect drier. Repeat steps 1) and 2) of «RESIDUAL PRESSURE CHECK»(/ford/ltd-crown-victoria/i-1983-1991/remont/electronic-suspension/#suspension-automatic-level-control__residual-pressure-check) . Perform «SYSTEM OPERATION CHECK»(/ford/ltd-crown-victoria/i-1983-1991/remont/electronic-suspension/#suspension-automatic-level-control__system-operation-check) .

MONITOR LIGHT OPERATION

1. Turning the ignition switch from "OFF" to "RUN" will cause monitor light to flash. The monitor light flashes once per second while compressor relay is on.
2. The light stays on while ignition is on and one or more of the following occur: height sensor wire connector is detached, an air line is removed, vent solenoid is on over one minute or compressor relay is on over 2 minutes.
3. Whenever an abnormal program run is detected, the microcomputer module suspends all controls and the monitor light stays on. All system functions of the module, except compressor relay on, are energized for 29-31 minutes after the ignition is turned off.
4. To reset the system, cycle the ignition switch from "OFF" to "RUN" position.

DIAGNOSTIC TESTING

Note. To perform diagnostic testing, an analog volt/ohmmeter, a jumper lead and a test light with No. 194 bulb must be used. Use of any other type of testing equipment may damage system or give false readings.

Construct test light using a No. 194 bulb, one lead with a pointed probe end and the other lead with a clip end. Connect test light before cycling ignition switch from "RUN" to "OFF" position.

When performing tests, observe when ignition switch is cycled, ensure that the module vent solenoid timer and compressor timer are operating properly.

Perform tests without disconnecting the harness at the module connector, unless stated in individual tests. The compressor relay, vent solenoid and height sensor have internal diodes for noise suppression. DO NOT reverse polarity.

TEST CHART MENU

QUICK REFERENCE TEST CHART

Note. During installation always reconnect negative battery cable last.

Removal & Installation

1. Disconnect negative battery cable. Remove air line from drier by pushing in on retainer and pulling air line out. Remove wiring connector from air compressor by pulling up and away from bracket. Disconnect wiring from connector.
2. Remove 3 compressor-to-bracket mounting bolts and remove compressor. Remove 2 nuts from inside wheelwell and one bolt from engine compartment. Remove mounting bracket.
3. To install, reverse removal procedure. Tighten compressor-to-bracket bolts to specification. Reconnect negative battery cable. Check air lines for leakage. Check for proper system operation.

1. Disconnect negative battery cable. Remove wiring connector from air compressor by pulling up and away from bracket. Disconnect wiring connector. Remove air compressor from mounting bracket.
2. Remove drier-to-compressor retaining screw. Twist drier clockwise to disengage from air compressor. Remove drier and "O" ring. Discard "O" ring.
3. To install, reverse removal procedure. Install new "O" ring and ensure it is properly seated on drier end. Install drier into compressor and twist counterclockwise. Tighten retaining screw to specification. Connect negative battery cable. Check system for proper operation.

Removal & Installation (All Except Wagon Models)

1. Disconnect negative battery cable. Remove right side trunk trim panel. Disconnect module connector by pushing in on retainer and pulling up on connector. Remove 2 microcomputer mounting bolts.
2. Remove module. Remove "U" nuts from module. To install, reverse removal procedure. Connect negative battery cable. Tighten module retaining bolts to specification.

Removal & Installation (Wagon Models)

Disconnect negative battery cable. Remove right rear spare tire cover or trim panel. Disconnect module connector by pushing in on retainer and pulling downward on connector. Remove module. To install, reverse removal procedure. Connect negative battery cable. Tighten module retaining bolts to specification. Check for proper operation.

1. Disconnect battery ground cable. Disconnect sensor connector, located on sensor mounting bracket underneath luggage compartment. Unlatch connecting link snap lock.
2. Disconnect connecting link from upper control ball stud. Remove 2 sensor mounting bolts and remove sensor. To install, reverse removal procedure. Tighten sensor mounting bolts to specification. Connect negative battery cable. Check for proper system operation.

REAR SHOCK ABSORBERS

Note. Air shocks may be replaced separately. Replace only faulty shocks.

1. Disconnect height sensor connector link with the ignition off before allowing rear axle to hang free. Raise vehicle. The vent solenoid will vent air while vehicle is on jack or hoist. Wait until air has stopped "hissing" before disconnecting air lines.
2. A residual pressure of 8-24 psi will remain in air lines. Disconnect air lines by pushing in on retainer ring(s) and pulling out on line(s). Remove nut from upper shock retaining stud. Remove nut from lower shock stud. Remove shock absorber.
3. To install, reverse removal procedure. Tighten mounting nuts to specification. Ensure shock absorber rubber sleeve are marked and indexed properly.

Scheme 3

Scheme 4

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

TEST A - VEHICLE LOAD CHECK

Check vehicle passenger and luggage compartments for overloading. Unload as necessary. If ride height is okay, perform SYSTEM OPERATION CHECK . Adjust ride height as necessary.

TEST B - POWER MONITOR LIGHT

1. Connect test light probe lead to circuit 37, pin 5, at module connector (battery B+). Connect clip lead to ground. If test light is on, proceed to step 2). If test light is off, proceed to TEST E. NOTE: Test light must remain connected during individual test unless otherwise noted.
2. Connect lead with clip to the diagnostic pigtail, circuit 693, pin 7, near the module connector. If test light is off, proceed to TEST C. If test light is on, recycle ignition switch from "RUN" to "OFF". If light remains on, replace module. Perform «SYSTEM OPERATION CHECK»(/ford/ltd-crown-victoria/i-1983-1991/remont/electronic-suspension/#suspension-automatic-level-control__system-operation-check) .

TEST C - INITIALIZE SYSTEM

1. Before entering diagnostics, connect battery charger to the vehicle and leave on until diagnosis is complete. With ignition off, repeat TEST B. Review monitor light service functions. Turn ignition switch to the "RUN" position. Observe monitor test light. Light will normally be off, then start blinking after 7-13 second delay if there is a signal to raise the rear of the vehicle from the height sensor.
2. If light blinks, compressor runs and vehicle raises, proceed to step 5). If light comes on immediately, abnormal program is detected, proceed to TESTS G, H and J. If light blinks, compressor runs, but vehicle does not raise, check system for leaks. Check sensor link attachment. Compressor times out after 2 minutes of continuous running.
3. If light blinks, but compressor does not run and vehicle does not raise, proceed to TESTS D, E and K. If light does not turn on, but compressor runs and vehicle raises, proceed to TEST B. Reinitialize system and observe light.
4. If light is off, compressor does not run and vehicle does not raise, vehicle is operating normally. Vehicle is at ride height or high position. Proceed to step 5). If light is off, compressor runs, but vehicle does not raise, check light. Check system for leaks. Perform «SYSTEM OPERATION CHECK»(/ford/ltd-crown-victoria/i-1983-1991/remont/electronic-suspension/#suspension-automatic-level-control__system-operation-check) .
5. Is light off during first 60 seconds after the ignition switch is turned to the "RUN" position? If light is off, vent solenoid clicks during the first 15 seconds and the vehicle lowers, proceed to step 7). If light is off, vent solenoid does not click and vehicle does not lower, proceed to step 7).
6. If light is on continuously, proceed to TESTS F, G, H and J.
7. Is light on after the first 60 seconds after the ignition switch is turned to the "RUN" position? If light is on, vent solenoid clicks within first 15 seconds and vehicle does/does not lower, this is normal operation. Vent solenoid timed out. Proceed to step 9).
8. If light is off, vent solenoid does not click within the first 15 seconds and vehicle does/does not lower, check test light. Vehicle may be in ride height position. Proceed to step 9).
9. Apply a 300 lb. (136 kg) load to the rear of the vehicle. Does light turn off within 15 seconds. If light turns off, vent time out function is okay. Proceed to step 10). If light does not turn off after 15 seconds, check vent solenoid. Replace module. Cycle ignition off. Perform «SYSTEM OPERATION CHECK»(/ford/ltd-crown-victoria/i-1983-1991/remont/electronic-suspension/#suspension-automatic-level-control__system-operation-check) . NOTE: Compressor may run after this time. Allow vehicle to vent and reach ride height position before proceeding to next step.
10. Disconnect air line at drier. Cycle ignition switch from "OFF" to "RUN" position. Apply a 300 lb. (136 kg) load to the rear of the vehicle. Does light turn on after 115-125 seconds and the compressor stop? If light turns on and compressor stops, compressor run timer is okay. Time begins when the compressor starts to run. Reconnect air line. Remove weight from rear of vehicle. Perform «SYSTEM OPERATION CHECK»(/ford/ltd-crown-victoria/i-1983-1991/remont/electronic-suspension/#suspension-automatic-level-control__system-operation-check) . NOTE: Light may turn off and air may escape when the line is removed.
11. If light does not turn on and compressor does not stop, replace module. Repeat step 10). Perform «SYSTEM OPERATION CHECK»(/ford/ltd-crown-victoria/i-1983-1991/remont/electronic-suspension/#suspension-automatic-level-control__system-operation-check) .

TEST D - IGNITION CIRCUIT CHECK

1. Set voltmeter to the 12-volt scale. Connect negative lead to the module mounting screw. Connect positive lead to ignition power circuit 298, pin 4, at the module connector. Turn ignition off and remove battery charger.
2. If there is 0 volts, circuit from ignition sensor to module is okay. Proceed to step 3). If there is voltage, repair short to module on circuit 298, between module connector and ignition switch. Repeat step 1).
3. Cycle ignition switch to the "RUN" position. Compressor may run and raise vehicle, or vent solenoid may operate and lower vehicle. If voltage is more than 10 volts, circuit between ignition switch and module is okay. Proceed to TEST E.
4. If voltage is less than 10 volts, repair open or short circuit to ground on circuit 298. Check fuses. Repair low voltage condition due to faulty connection, open fuse or low battery. Repeat step 3). Perform «SYSTEM OPERATION CHECK»(/ford/ltd-crown-victoria/i-1983-1991/remont/electronic-suspension/#suspension-automatic-level-control__system-operation-check) .

TEST E - BATTERY CIRCUIT CHECK

1. Turn ignition off and remove battery charger. Set voltmeter to the 12-volt scale. Connect negative voltmeter lead to module mounting screw. Connect positive voltmeter lead to module power circuit 37, pin 5, at the module connector. NOTE: With ignition off and 30-minute timer activated. Solenoid may click and vehicle may or may not lower.
2. If voltage is more than 10 volts and steady, battery circuit to the module is okay. Perform TEST B. If voltage is less than 10 volts, repair low voltage condition due to faulty connection, low battery or fusible link at starter relay on circuit 37. Reconnect connectors as necessary. Repeat step 1).

TEST F - VENT SOLENOID SYSTEM CHECK

1. Check monitor light. Remove battery charger and cycle ignition switch to the "OFF" position. If monitor light is off, test is okay. If monitor light is on 55 seconds after ignition was turned off, vent time out is okay. Proceed to step 2).
2. Set voltmeter to the 12-volt scale. Connect negative voltmeter lead to the module mounting screw. Connect positive voltmeter to circuit 415, pin 9, at the module connector. If voltage reading is more than 8.5 volts and steady, circuit between vent solenoid and module is okay. Proceed to step 3). If voltage is less than 8.5 volts, check battery voltage. Proceed to step 3).
3. Remove positive lead from voltmeter and touch to a good ground. If the vent solenoid clicks, vent solenoid and circuit 415 to the module are okay. Reconnect test lead and proceed to step 4). If vent solenoid does not click, reconnect test lead and proceed to step 5).
4. Raise rear bumper with a floor jack. Cycle ignition switch from "RUN to "OFF" position. If light is on after 55 seconds, check sensor circuits. Replace module. Perform «SYSTEM OPERATION CHECK»(/ford/ltd-crown-victoria/i-1983-1991/remont/electronic-suspension/#suspension-automatic-level-control__system-operation-check) .
5. Move positive voltmeter lead to solenoid feed circuit 37 at the compressor connector. Disregard monitor light. If voltage reading is more than 8.5 volts and steady, solenoid feed circuit from battery relay is okay. Proceed to step 6). If voltage is less than 8.5 volts and steady, repair low voltage condition or open in feed circuit 37 from the starter relay to the connector. Repeat step 5).
6. Move positive voltmeter lead to solenoid control circuit 415 at the compressor connector. Disregard monitor light. If voltage reading is more than 8.5 volts and steady, vent solenoid is okay. Proceed to step 7). If voltage is less than 8.5 volts, vent solenoid is inoperative. Replace compressor assembly. Repeat step 6).
7. Move positive voltmeter lead to control circuit 415, pin 9, at the module connector. Disregard monitor light. If voltage is less than 8.5 volts, repair open in control circuit 415 between module connector and compressor connector. Repeat step 7). If voltage is more than 8.5 volts, solenoid circuit is okay. Proceed to TEST H.

TEST G - SENSOR GROUND CIRCUIT CHECK

1. Cycle ignition switch from on to off. Remove battery charger. Disconnect connector from module. Connect negative ohmmeter lead to the module mounting screw. Connect positive lead to module pin 5. Disregard monitor light. If resistance is more than 2 ohms, record reading. Proceed to step 2). If reading is less than 2 ohms, sensor ground circuit through module is okay. Proceed to step 2).
2. Connect positive ohmmeter lead to circuit 431, pin 3, at the module connector. Move negative ohmmeter lead to ground circuit 430, pin 10, at the module connector. If resistance is more than 8 ohms, proceed to step 3). If resistance is less than 8 ohms, sensor circuit to ground is okay. Proceed to TEST H.
3. Disconnect rear harness sensor connector at underbody. On sedan models, push harness grommet up inside luggage compartment. On wagon models, use longer test leads. Move the positive ohmmeter lead to ground circuit 430 at the harness sensor connector. If resistance is more than 2 ohms, proceed to step 4).
4. Move the positive voltmeter lead to power circuit 431 at the harness connector. Move negative lead to circuit 431, pin 3, at the module connector. If resistance is more than 2 ohms, repair open in sensor circuit 431 between module connector and sensor connector. Repeat step 4). If resistance is less than 2 ohms, circuit 431 is okay, proceed to step 5).
5. Move positive test lead to sensor connector circuit 431 (sensor side). Move negative test lead to sensor connector circuit 430 (sensor side). If resistance is more than 18 ohms, replace sensor. Perform «SYSTEM OPERATION CHECK»(/ford/ltd-crown-victoria/i-1983-1991/remont/electronic-suspension/#suspension-automatic-level-control__system-operation-check) . If resistance is less than 18 ohms, proceed to step 6).
6. Connect all disconnected connectors. Perform procedure outlined in step 1). If resistance is less than 20 ohms, system is okay. If resistance is more than 20 ohms, replace module. Perform «SYSTEM OPERATION CHECK»(/ford/ltd-crown-victoria/i-1983-1991/remont/electronic-suspension/#suspension-automatic-level-control__system-operation-check) .

TEST H - SENSOR POWER CIRCUIT CHECK

1. Connect module connector, if disconnected. Set voltmeter to 5-volt scale. Connect voltmeter negative lead to module mounting screw. Connect positive lead to sensor power circuit 431, pin 3, at module connector. Cycle ignition switch from "RUN" to "OFF" position. Disregard monitor light. Vent solenoid may click. Observe voltmeter. NOTE: Voltage check must be made within 30 minutes of cycling ignition switch, or voltage will return to zero.
2. If voltage is 5 volts and steady, module output power is okay. Proceed to step 3). If voltage is more than 5.3 volts, replace module. Repeat step 1). Perform «SYSTEM OPERATION CHECK»(/ford/ltd-crown-victoria/i-1983-1991/remont/electronic-suspension/#suspension-automatic-level-control__system-operation-check) . If voltage is less than 4.7 volts, repeat step 1). If still less than 4.7 volts, replace module. Perform «SYSTEM OPERATION CHECK»(/ford/ltd-crown-victoria/i-1983-1991/remont/electronic-suspension/#suspension-automatic-level-control__system-operation-check) .
3. Move positive test lead to sensor circuit 427, pin 1, at module connector. Disregard monitor light. If voltage is more than 4.1 volts, module output power is okay. Proceed to step 5). If voltage is 1.3-4.1 volts, sensor is switching electrically from a low-to-high or a high-to-low state. Add 300 lb. (136 kg) to rear of vehicle and repeat step 3).
4. If voltage is less than 1.3 volts, but more than zero volts, module output power is okay. Proceed to step 5). If there is zero volts, recycle ignition switch to "RUN" and then to "OFF" position. Repeat step 3). If voltage is still zero volts, proceed to TEST G.
5. Move positive test lead to sensor circuit No. 428, pin 6, at module connector. Disregard monitor light. If voltage is greater than 4.1 volts, or between zero and 1.3 volts, module power circuit is okay. Proceed to TEST J.
6. If voltage is 1.3-4.1 volts, add 300 lbs. (136 kg) to rear of vehicle. Repeat step 5). If there is zero volts, recycle ignition switch to "RUN" and then to "OFF" position. Repeat step 5). If voltage is still zero volts, proceed to TEST G.

TEST J - SENSOR LOGIC CIRCUIT CHECK

1. Connect module connector. Disconnect rear harness sensor connector at underbody. Turn ignition off. Set voltmeter to 5-volt scale. Connect negative test lead to the module mounting screw. Connect positive test lead to sensor circuit No. 427, pin one, at the module connector. Disregard monitor light if connected. Test must be completed within 30 minutes. If not, recycle ignition switch to "RUN" and then "OFF" position to reset timer, as required.
2. If voltage is more than 4.3 volts, proceed to step 3). If voltage is less than 4.3 volts, recycle ignition switch to "RUN" and then to "OFF" position. Repeat step 1). Replace module. Perform «SYSTEM OPERATION CHECK»(/ford/ltd-crown-victoria/i-1983-1991/remont/electronic-suspension/#suspension-automatic-level-control__system-operation-check) .
3. Move positive lead to sensor circuit No. 428, at rear harness sensor connector. If voltage is more than 4.3 volts, proceed to step 4). If voltage is less than 4.3 volts, recycle ignition switch from "RUN to "OFF position. Repeat step 3). Replace module. Perform «SYSTEM OPERATION CHECK»(/ford/ltd-crown-victoria/i-1983-1991/remont/electronic-suspension/#suspension-automatic-level-control__system-operation-check) .
4. Move positive test lead to sensor circuit No. 428, at rear harness sensor connector. If voltage is more than 4.3 volts, harness circuit is okay. If voltage is less than 4.3 volts, repair open in circuit No. 428, between module connector and sensor harness connector. Repeat step 4).
5. Move positive test lead to sensor circuit No. 427, at rear harness sensor connector. If voltage is more than 4.3 volts, harness circuit is okay. If voltage is less than 4.3 volts, repair open in circuit No. 427, between module connector and sensor harness connector. Repeat step 5).
6. Disconnect module connector, move negative lead of ohmmeter to circuit No. 427 at module connector. Ohmmeter should read less than 2 ohms to indicate circuit No. 427 is okay. Perform «SYSTEM OPERATION CHECK»(/ford/ltd-crown-victoria/i-1983-1991/remont/electronic-suspension/#suspension-automatic-level-control__system-operation-check) . If ohmmeter reads more than 2 ohms, circuit No. 427 and circuit No. 428 are crossed. Switch circuit leads at module or sensor harness pin connector. Repeat step 6).

TEST K - COMPRESSOR RELAY MOTOR CHECK

1. Cycle ignition switch from "RUN" to "OFF" position. Set voltmeter to 12-volt scale. Disregard monitor light. Relay and/or vent relay may click. Connect positive test lead to circuit No. 420, pin 8, at the module connector. If voltage is less than one volt, proceed to step 2). If voltage is more than one volt, repair short to module connector on circuits No. 298 and No. 420, between ignition switch relay and module connector. Repeat step 1).
2. Disconnect module harness from control module connector. Cycle ignition switch from "OFF" to "RUN" position. Connect positive test lead to module harness connector circuit No. 420. If voltage is more than 8 volts, compressor relay control circuits No. 298 and No. 420 to the module are okay. Proceed to step 3). If voltage is less than 8 volts, repair low voltage condition due to faulty connection relay, low battery or blown fuse on circuits No. 298 and 420. Repeat step 2).
3. Remove positive test lead from voltmeter and touch module mounting screw. Compressor relay should click. Touch test lead several times to ensure relay clicking can be heard. If compressor relay clicks, compressor relay coil is okay. Reconnect test lead to voltmeter. Proceed to step 4). If compressor relay does not click, replace relay. Repeat step 3). Perform «SYSTEM OPERATION CHECK»(/ford/ltd-crown-victoria/i-1983-1991/remont/electronic-suspension/#suspension-automatic-level-control__system-operation-check) .
4. Check compressor motor. Repeat step 3). If compressor motor cycles, compressor and ground are okay. Reconnect test lead to voltmeter. Proceed to TEST G. If compressor does not cycle, reconnect test lead to voltmeter. Proceed to step 5).
5. Move test lead to circuit No. 37 at the harness side of the compressor relay connector. If voltage is more than 8 volts, battery feed circuit to the compressor relay is okay. Proceed to step 6). If voltage is less than 8 volts, repair open or short to ground on circuit No. 37, between battery and relay connector. Check fusible link and battery condition. Repeat step 5).
6. Connect jumper lead between circuit No. 420, pin No. 8, at the module connector located in luggage compartment and a mounting screw. Relay should click. Compressor may cycle. If relay clicks, remove jumper wire from mounting screw. Proceed to step 7). If relay does not click, proceed to step 7).
7. Move positive test lead to compressor motor feed circuit No. 417 at the harness side of the compressor motor connector. Touch the meter lead to the module mounting screw. Voltage reading should be more than 8 volts. Relay should click. Compressor may cycle. If voltage is more than 8 volts and relay clicks, remove jumper lead. Proceed to step 8). If voltage is less than 8 volts, and relay does not click, repair open or short to ground on circuit No. 417 between relay and motor connector, or replace as necessary. Repeat step 7).
8. Touch test lead to module mounting screw. Compressor motor should cycle. If motor cycles, motor circuit is okay. Replace module. Perform «SYSTEM OPERATION CHECK»(/ford/ltd-crown-victoria/i-1983-1991/remont/electronic-suspension/#suspension-automatic-level-control__system-operation-check) . If motor does not cycle, remove jumper lead from mounting screw. Proceed to step 9).
9. Disconnect compressor connector. Connect ohmmeter positive to feed circuit No. 417 at motor connector. Connect negative lead to circuit No. 57 at motor connector. Ohmmeter reading should be less than 2 ohms. If ohmmeter reading is less than 2 ohms, compressor and circuit breaker are okay. Proceed to step 10). If reading is more than 2 ohms, replace compressor motor. Reconnect compressor and module connectors. Perform «SYSTEM OPERATION CHECK»(/ford/ltd-crown-victoria/i-1983-1991/remont/electronic-suspension/#suspension-automatic-level-control__system-operation-check) .
10. Move negative test lead to motor ground circuit No. 57 at harness side of compressor connector. Move positive test lead to ground circuit No. 57, pin No. 11, at the module harness connector. Move positive test lead to body eyelet, ground circuit 57. Ohmmeter should indicate less than 2 ohms at both points.
11. If ohmmeter reading is less than 2 ohms, ground circuit is okay. Reconnect motor and module connectors. Perform «SYSTEM OPERATION CHECK»(/ford/ltd-crown-victoria/i-1983-1991/remont/electronic-suspension/#suspension-automatic-level-control__system-operation-check) . If readings are not less than 2 ohms, repair open in circuit No. 57 between motor harness and ground and/or between module pin No. 11 and ground. Repeat step 10).

Automatic Leveling System Wiring Diagram. Scheme 5

See also:
• DIAGNOSTIC TESTING
• RESIDUAL PRESSURE CHECK
• SYSTEM OPERATION CHECK