Suspension - Rear Level Control Cadillac Brougham I

DESCRIPTION

Rear level control automatically adjusts rear height of vehicle regardless of load. System is activated when ignition is on and weight is added or removed from vehicle.

Electronic Level Control (ELC) consists of a compressor, air drier, exhaust solenoid, compressor relay, height sensor, air adjustable shock absorbers, pressure limiter, and connecting air lines.

Air drier contains a moisture absorbing chemical and also contains valving to maintain a minimum system pressure of approximately 15-22 psi (1.0-1.5 kg/cm 2 ) on DeVille and Fleetwood and 7-14 psi (.5-.9 kg/cm 2 ) on all other models. A pressure limiter valve prevents pressure from exceeding 64-74 psi (4.5-5.2 kg/cm 2 ).

RAISING VEHICLE

When weight is added to vehicle, height sensor arm rotates upward. Rotating arm upward grounds compressor relay circuit. After a time delay of 8-14 seconds on "A", "B" bodies and Bonneville, or 13-27 seconds on all others, grounding of compressor relay turns air compressor on, causing vehicle to rise.

As vehicle rises, height sensor rotates downward to curb height position. When vehicle is within 1" (25.4 mm) of curb height, height sensor opens ground circuit to compressor relay, turning compressor off.

LOWERING VEHICLE

When weight is removed from vehicle, height sensor arm rotates downward. After a time delay of approximately 8-14 seconds on "A", "B" bodies and Bonneville, or approximately 13-27 seconds on all others, downward rotation of the arm grounds exhaust solenoid valve circuit. Energizing exhaust solenoid valve causes air to vent through air drier and out of exhaust solenoid valve.

As vehicle lowers, height sensor arm rotates upward to curb height position. When vehicle is within 1" (25.4 mm) of curb height, height sensor opens exhaust solenoid valve circuit, causing exhaust solenoid valve to close.

AIR REPLENISHMENT

In order to ensure the system is operating with at least minimum air pressure, the height sensor commands an air replenishment cycle each time the ignition is cycled on. An internal timer circuit is activated when ignition switch is turned to "ON" position. After a delay of approximately 35-45 seconds, compressor turns on for 3-5 seconds to ensure residual system pressure.

If weight is added or removed from vehicle during 35-45 second delay, air replenishment cycle will be overridden and vehicle will raise or lower after normal time delay.

HEIGHT SENSOR

To increase vehicle riding height, move plastic arm upward and tighten lock nut. To lower riding height, loosen lock nut and move plastic arm down and tighten lock nut. If adjustment cannot be made, check for proper sensor application. (Scheme 6)

Scheme 6

RIDING HEIGHT

See RIDING HEIGHT SPECIFICATIONS article in WHEEL ALIGNMENT section.

CAR LOADED, WILL NOT RISE

Leaks in air lines, fittings or shock absorbers. Pinched lines between compressor and shock absorbers. Defective height sensor. Compressor inoperative. Loose or damaged electrical connections to sensor or compressor.

CAR LOADED, RISES, THEN LEAKS DOWN

Severe leak in lines, fittings or shock absorbers.

CAR LOADED, RISES PARTIALLY

Height sensor out of adjustment. Compressor or wiring defective.

CAR RISES WHEN LOADED, LEAKS DOWN WHEN DRIVING

Defective drier or compressor. Pinched air lines or leaks in fittings or air lines.

CAR RIDES HIGH

Height sensor out of adjustment. Drier plugged or air lines pinched. Poor electrical connections.

SYSTEM OPERATIONAL TEST

1. Unload vehicle. With ignition off, check riding height. Turn ignition on. Add 300-350 lbs. (136-159 kg) load to trunk. Compressor should start operating within approximately 7-10 seconds. Vehicle should rise to within 3/4" (19 mm) of riding height.
2. Remove load from trunk. Exhaust should start within approximately 7-10 seconds. Within 2 minutes, exhaust should stop and vehicle should be within 3/4" (19 mm) of riding height.

SYSTEM LEAK TEST

1. Install Pressure Gauge (J22124-A) in-line between drier assembly and pressure regulator valve. Install gauge so shut-off valve is on compressor side of gauge. With shut-off gauge open, apply shop air pressure through the service valve until valve reaches 100 psi (7.03 kg/cm 2 ).
2. If a leak is indicated, close shut-off valve and continue to watch for a pressure drop. If pressure continues to drop, leak is external from the compressor. Leak test all connections. If pressure stops decreasing after shut-off valve is closed, leak is in the compressor assembly.
3. Check compressor for leaks. If pressure builds up rapidly, but vehicle does not raise, check for pinched air line or stuck or binding shocks.

Brougham, Eldorado, Seville & Toronado

1. Disconnect pressure line from dryer. Attach pressure gauge to dryer. Disconnect negative (Black) wire from compressor bracket. Install an ammeter between negative wire and compressor bracket. If testing on vehicle, ground ALDL terminal "K".
2. If testing off vehicle, apply 12 volts to compressor connector pin "B" and ground pin "D". With pressure gauge reading should be 100 psi (7.03 kg/cm 2 ) minimum and ammeter reading should be 10 amps maximum.
3. Disconnect wiring and check compressor for leakdown. Replace compressor if readings are not as specified or internal leakdown is indicated.

Riviera

1. Disconnect pressure line from drier and attach Air Pressure Gauge (J22124-A) to drier fitting. Disconnect wiring from compressor motor and exhaust solenoid terminals. (Scheme 7)
2. Connect 12-volt power supply to compressor through ammeter. Current draw must not exceed 14 amps. Allow pressure to reach 100 psi (7.03 kg/cm 2 ) minimum and shut off compressor. Allow pressure to stabilize. Check for pressure leaks.
3. If compressor is allowed to run to maximum output pressure of 180 psi (12.7 kg/cm 2 ), the solenoid exhaust valve will act as a relief valve. This gives a false indication of system leakage. If compressor operates correctly, reconnect wiring and air lines. If compressor does not operate correctly, refer to TROUBLE SHOOTING in this article.

Scheme 7

1. Raise vehicle on hoist. Ensure all electrical connectors are properly mated. Cycle ignition off and on to reset sensor timing circuits. After a 35-45 second delay, compressor should run for 4 seconds. Disconnect height sensor link from control arm.
2. Move control arm upward. There should be a 13-27 second delay before compressor starts to run. As soon as struts start to fill, move control arm downward. After a 13-27 second delay, struts should start to deflate. Replace height sensor if it fails any of these tests.

1. Cycle ignition switch to the "ON" position. Raise vehicle on hoist. Ensure axle housing is supported as close to ride height specification as possible. Check all wiring for good connections. Disconnect link from height sensor arm.
2. Move sensor arm upward. After a 8-14 second delay on "A" and "B" bodies, and Bonneville or 13-27 second on all other models, the compressor should run and shock absorbers should start to inflate. As soon as shock absorber air boots fill, stop compressor by moving sensor arm down.
3. Move sensor arm below position where compressor stopped running. There should be a delay before shock absorbers start to deflate and vehicle lowers. Replace height sensor if it does not function correctly.

ELC SYSTEM TEST

1. Open hood and trunk. Turn ignition switch to "OFF" position. Check vehicle height at rear wheel openings. Reset ELC system by cycling ignition off and on. Leave ignition switch in "ON" position, engine off. Add 300 lbs. load to trunk.
2. If compressor starts within 28 seconds, go to step 3). If compressor does not start within 28 seconds, but vehicle is within 1" of unloaded height, go to NO EXHAUST TEST. If vehicle is not within 1" of unloaded height, adjust height sensor and retest system. If system is still not okay, go to COMPRESSOR DOES NOT OPERATE TEST.
3. If compressor stops within 7 minutes, go to next step. If compressor runs continuously, check for a stuck relay, short to ground in circuit No. 321 or short to voltage in circuit No. 322. If okay, replace height sensor.
4. If vehicle returns to within 1" of unloaded height, go to next step. If system leaks down, go to IMPROPER OR CONTINUOUS EXHAUST TEST. If vehicle is not within 1" of original height, adjust height sensor and retest. If still not okay, go to IMPROPER OR CONTINUOUS EXHAUST TEST.
5. Remove load from trunk. If no exhaust is present after 28 seconds, go to NO EXHAUST TEST. If system exhausts within 28 seconds but vehicle does not return to within 1" of original height after 2 minutes, adjust height sensor and retest. If system exhausts within 28 seconds and vehicle returns to within 1" of original height after 2 minutes, system is okay.

COMPRESSOR DOES NOT OPERATE TEST

1. Turn ignition to "ON" position. On Brougham, ground ELC test connector located on Yellow wire near ELC compressor. On other models, apply 12 volts to compressor pin "B" and ground to pin "D". On all models, if compressor does not run, go to step 3). If compressor runs, go to next step.
2. Disconnect height sensor harness connector. (Scheme 8) Using a jumper wire, jump pins "A" and "F" (Brougham) or "A" and "B" (all other models) of height sensor body wiring harness connector. If compressor does not run, check for an open in circuit No. 151 (Brougham, Black wire), No. 803 (all other models, Black/White wire), or 321 (all models, Yellow wire). If compressor runs, go to RESET CIRCUIT OPERATIONAL TEST.
3. Remove ELC relay. Check for battery voltage at pin No. 2 (Brown/White wire) of relay cavity. If battery voltage is present, go to next step. If not, check "GA-Trans" fuse on Brougham or ELC compressor fuse on all other models. If okay, repair open in circuit No. 39 (Brougham, Pink/Black wire) or No. 650 (all other models, Brown/White wire).
4. Using a jumper wire, jump pins No. 1 and 4 (Brougham) or pins No. 2 and 3 of ELC relay cavity (all other models). If compressor does not run, go to next step. If compressor runs, check for an open in circuit No. 321 (Yellow wire). If okay, replace ELC relay.
5. Disconnect compressor harness connector. Apply 12 volts to pin "B" and ground pin "D". If compressor runs, check for open in circuit No. 151 (Brougham), No. 804 (all other models) or No. 322 (Dark Green wire). If compressor does not run, repair compressor motor.

IMPROPER OR CONTINUOUS EXHAUST TEST

Check for a short to ground in circuit No. 320 from compressor to height sensor. If a short is present, repair short. If a sort is not present, do a compressor performance test. See COMPRESSOR PERFORMANCE TEST under SYSTEM TESTING in this article. If not okay, replace compressor. If okay, perform SYSTEM LEAK TEST. If okay, replace height sensor. If not okay, repair leak.

NO EXHAUST TEST

1. Cycle ignition on and off to reset system. Disconnect compressor harness connector. On Brougham, check for voltage at harness connector pin "A". On all other models, check for voltage at harness connector pin "C". If battery voltage is present, go to next step. If no voltage is present, check fuse and replace as necessary. If fuse is okay, repair open in circuit No. 840.
2. Disconnect compressor harness. Disconnect height sensor harness connector. Using a jumper wire, jump terminals "A" and "E". If system does not exhaust, go to next step. If system exhausts, check for voltage at pin "C". If no voltage is present, repair open in circuit No. 40 (Brougham, Orange wire) or No. 840 (all other models, Orange/Black wire). If voltage is present, replace height sensor.
3. On Brougham, apply 12 volts to pin "A" and ground pin "C". On all other models, apply 12 volts to pin "C" and ground pin "A" of compressor harness connector. If system does not exhaust, replace exhaust solenoid. If system does exhaust, repair open in circuit No. 151 (Brougham, Black wire), No. 803 (all other models, Black wire) or No. 320 (all models, White wire).

RESET CIRCUIT OPERATIONAL TEST

1. Turn ignition off. Disconnect height sensor harness. On Brougham, check for voltage at pins "B" and "C". On all other models, check for voltage at pins "C" and "D". If no voltage is present at pin "B" (Brougham) or "D" (all others) and battery voltage is present at pin "C", go to next step. If voltage is present at pin "B" (Brougham) or "D" (all others), repair short to voltage in circuit No. 39 (Brougham), or No. 650 or 750 (all others). If zero voltage is present at pin "C", check fuse. If fuse is okay, repair open in circuits No. 40 and 340 (Brougham), or 840 (all others).
2. Turn key to "ON" position. On Brougham, check voltage at pin "B". On all others, check voltage at pin "D". If battery voltage is present, go to next step. If zero voltage is present, check fuse and replace as necessary. If okay, repair open in circuit No. 750.
3. Check voltage from pin "C" to pin "A". If battery voltage is present, replace height sensor. If not, repair open in circuit No. 151 (Brougham) or No. 803 (all others).

HEIGHT SENSOR OPERATIONAL TEST

1. Raise vehicle on hoist. Ensure harness connectors are attached to height sensor and at body wiring harness connector. Cycle ignition off, then on, to reset height sensor timer circuit. After a delay of 35-45 seconds, compressor should operate for approximately 4 seconds.
2. Disconnect height sensor link from control arm. Move sensor arm upward. There should be a 13-27 second delay before compressor starts and struts begin to inflate. When strut air boots noticeably fill, move sensor arm down and stop compressor.
3. Move sensor arm down below position where compressor stopped. There should be a 13-27 second delay before struts start to deflate and vehicle lowers.

ELC HEIGHT SENSOR

Removal & Installation

Disconnect negative battery cable. Disconnect height sensor harness. Raise and support vehicle. Disconnect height sensor link from height sensor actuating arm. Remove 2 height sensor mounting screws. To install, reverse removal procedure. Tighten sensor mounting bolts to specification. Adjust height sensor.

Removal

1. Disconnect negative battery cable. Raise vehicle on hoist. Disconnect compressor electrical connectors and air line from drier. Remove pressure limiter retaining clip from compressor bracket (if equipped).
2. Remove rear strut feed line from pressure limiter valve or air drier. Remove 3 mounting screws. Remove 3 compressor-to-bracket screws. Remove compressor.

Installation

To install, reverse removal procedure. Turn ignition on and allow system to cycle. Check for leaks using soap and water solution. (Scheme 8)

Scheme 8

Disconnect high pressure line by turning spring clip 90 degrees and removing tube assembly. Disconnect drier from compressor by turning spring clip and sliding dryer and "O" ring from compressor head assembly.

Note. Compressor is mounted on right side of vehicle on some models. Bracket will have to remove drier.

Lubricate "O" ring and install in port of compressor head. Return retainer spring to its original position. Install drier on compressor head assembly. If difficulty arises when installing drier in compressor head assembly, rotate slightly while applying pressure. Check system for leaks.

Removal & Installation

The air line used in system can be repaired by splicing in a coupling at leak area. Inflate system to 100 psi (7.03 kg/cm 2 ). Use a soap and water solution to locate leak. Deflate system through service valve and cut out leaking area. Install coupling and tighten to 6 ft. lbs. (8 N.m). Inflate system and check for leaks using a soap and water solution. (Scheme 9)

Scheme 9

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

Brougham ELC Wiring Diagram. Scheme 10

Eldorado & Seville Wiring Diagram. Scheme 11

Toronado Wiring Diagram. Scheme 12

Riviera Wiring Diagram. Scheme 13