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Suspension - Electronic Level Control Buick Electra VI

Electronic Suspension 5 illustrations ~2122 words

DESCRIPTION

Electronic Level Control (ELC) is a leveling system that automatically adjusts rear height of vehicle with varying loads on rear suspension. System is activated when ignition switch is "ON" and weight is added to or removed from vehicle.

System is made up 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 15-22 psi (1.0-1.5 kg/cm 2 ) on Cadillac DeVille and Fleetwood models and 7-14 psi (.5-1 kg/cm 2 ) on all other models. Pressure limiter valve prevents pressure at shocks 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 13-27 seconds, 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 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 13-27 seconds, 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 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 13-27 second 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 1)

Height Sensor Adjustment If adjustment is at end of slot, check for proper sensor application. Courtesy of General Motors Corp. Scheme 1

Scheme 1: Height Sensor Adjustment If adjustment is at end of slot, check for proper sensor application. Courtesy of General Motors Corp.
Scheme 1: Height Sensor Adjustment If adjustment is at end of slot, check for proper sensor application. Courtesy of General Motors Corp.

RIDING HEIGHT

See RIDING HEIGHT SPECIFICATIONS article in WHEEL ALIGNMENT section.

SYSTEM OPERATIONAL TEST

  1. Unload vehicle. With ignition off, check riding height. Turn ignition on (engine off). Reset "running time" by starting and running vehicle for a brief period of time.
  2. Add a 300 lb. (136 kg) load to trunk. Compressor should start operating within 27 seconds. Vehicle should rise to within 3/4" (19 mm) of riding height. Compressor should stop within 2 minutes.
  3. Remove load from trunk. Exhaust should start within 27 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, then 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.

COMPRESSOR PERFORMANCE TEST

  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 2)
  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»(/buick/electra/vi-1985-1990/remont/electronic-suspension/#suspension-electronic-level-control) in this article.

Scheme 2

Scheme 2
Scheme 2

HEIGHT SENSOR OPERATIONAL TEST

  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 13-27 second delay, 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 of 13-27 seconds before shock absorbers start to deflate and vehicle lowers. Replace height sensor if it does not function correctly.

ELC RELAY & COMPRESSOR MOTOR TEST NO. 1

Install a fused jumper wire between ELC test connector and ground. If compressor runs, proceed to ACTUATOR ARM TEST . If compressor does not run, check Yellow wire (No. 321) for an open. If Yellow wire (No. 321) is okay, proceed to ELC RELAY & COMPRESSOR MOTOR TEST NO. 2 .

ELC RELAY & COMPRESSOR MOTOR TEST NO. 2

Measure voltage at ELC connector between terminal "C" and ground. If voltage reads 12 volts, proceed to ELC RELAY & COMPRESSOR MOTOR TEST NO. 3 . If voltage does not read 12 volts, check Orange wire (No. 340) for an open.

ELC RELAY & COMPRESSOR MOTOR TEST NO. 3

Install a fused jumper wire at ELC connector between terminals "C" (Orange wire) and "A" (Dark Green wire). If compressor runs, replace ELC relay. If compressor does not run, leave fused jumper wire intact and proceed to ELC RELAY & COMPRESSOR MOTOR TEST NO. 4 .

ELC RELAY & COMPRESSOR MOTOR TEST NO. 4

  1. Measure and note voltage at harness half of ELC compressor connector between terminal "B" (Dark Green wire) and ground. If voltage does not read 12 volts, check Dark Green wire (No. 322) for an open.
  2. Measure voltage between terminals "B" (Dark Green wire) and "D" (Black wire). If voltage does not read 12 volts, check Black wire (No. 150) for an open. If both voltage checks show 12 volts, repair and/or replace compressor.

EXHAUST SOLENOID TEST NO. 1

  1. Install a fused jumper wire at ELC height sensor connector between terminal No. 2 and ground. If exhaust solenoid clicks and air begins to vent, reconnect connector and proceed to «ACTUATOR ARM TEST»(/buick/electra/vi-1985-1990/remont/electronic-suspension/#suspension-electronic-level-control__actuator-arm-test) .
  2. If exhaust solenoid does not click and air does not begin to vent, leave fused jumper wire intact and proceed to «EXHAUST SOLENOID TEST NO. 2»(/buick/electra/vi-1985-1990/remont/electronic-suspension/#suspension-electronic-level-control__exhaust-solenoid-test-no-2) .

EXHAUST SOLENOID TEST NO. 2

  1. Measure voltage at harness half of ELC compressor connector between terminal "A" and ground. If voltage reads 12 volts, replace exhaust solenoid. If voltage does not read 12 volts, check Orange wire (No. 340) for an open.
  2. Measure voltage between terminals "A" (Orange wire) and "C" (White wire). If voltage reads 12 volts, replace exhaust solenoid. If voltage does not read 12 volts, check White wire (No. 320) for an open.

ACTUATOR ARM TEST

Raise vehicle and ensure link is correctly attached and actuator arm is properly aligned.

ELC HEIGHT SENSOR TEST NO. 1

  1. With ignition switch in "RUN" position, measure voltage at ELC height sensor connector between terminal No. 6 and ground. If voltage reads 12 volts, reconnect connector and proceed to «ELC HEIGHT SENSOR TEST NO. 2»(/buick/electra/vi-1985-1990/remont/electronic-suspension/#suspension-electronic-level-control__elc-height-sensor-test-no-2) . If voltage does not read 12 volts, check Orange wire (No. 740) for an open.
  2. Measure voltage between terminals No. 6 (Orange wire) and No. 4 (Black wire). If voltage reads 12 volts, reconnect connector and proceed to «ELC HEIGHT SENSOR TEST NO. 2»(/buick/electra/vi-1985-1990/remont/electronic-suspension/#suspension-electronic-level-control__elc-height-sensor-test-no-2) . If voltage does not read 12 volts, check Black wire (No. 150) for an open to ground.
  3. Measure voltage between terminal No. 5 (Dark Blue wire) and ground. If voltage reads 12 volts, reconnect connector and proceed to «ELC HEIGHT SENSOR TEST NO. 2»(/buick/electra/vi-1985-1990/remont/electronic-suspension/#suspension-electronic-level-control__elc-height-sensor-test-no-2) . If voltage does not read 12 volts, check Dark Blue wire (No. 39) for an open.
  4. Measure voltage between terminal No. 3 (Yellow wire) and ground. If voltage reads 12 volts, reconnect connector and proceed to «ELC HEIGHT SENSOR TEST NO. 2»(/buick/electra/vi-1985-1990/remont/electronic-suspension/#suspension-electronic-level-control__elc-height-sensor-test-no-2) . If voltage does not read 12 volts, check Yellow wire (No. 321) for open.

ELC HEIGHT SENSOR TEST NO. 2

  1. Cycle ignition switch and return to "RUN" position. Raise vehicle and support rear axle at ride height. Disconnect link from actuator arm. Move actuator arm upward.
  2. If compressor does not begin to run after a 15-30 second delay, replace height sensor. If shocks do not begin to inflate and vehicle does not begin to move upward after 15-30 seconds, perform «SYSTEM LEAK TEST»(/buick/electra/vi-1985-1990/remont/electronic-suspension/#suspension-electronic-level-control__system-leak-test) and «COMPRESSOR PERFORMANCE TEST»(/buick/electra/vi-1985-1990/remont/electronic-suspension/#suspension-electronic-level-control__compressor-performance-test) .
  3. Slowly move arm downward until compressor stops. If compressor does not stop, replace height sensor. Continue to move actuator arm downward past the point where compressor stopped. If shocks do not begin to deflate and vehicle does not begin to lower after a 15-30 second delay, replace height sensor.

EXHAUST SOLENOID SHORT TEST

  1. Add 300 lbs. (136 kg) to luggage compartment. Disconnect ELC height sensor connector and ground ELC test connector with a fused jumper wire. Allow compressor to run for 2 minutes.
  2. If vehicle raises and maintains its height, replace height sensor. If vehicle does not rise or raises and leaks down, check White wire (No. 320) for a short to ground. If White wire (No. 320) is okay, perform «SYSTEM LEAK TEST»(/buick/electra/vi-1985-1990/remont/electronic-suspension/#suspension-electronic-level-control__system-leak-test) and «COMPRESSOR PERFORMANCE TEST»(/buick/electra/vi-1985-1990/remont/electronic-suspension/#suspension-electronic-level-control__compressor-performance-test) .

Electra, Park Avenue & Ninety-Eight ELC Electrical Diagram. Scheme 3

Scheme 3: Electra, Park Avenue & Ninety-Eight ELC Electrical Diagram
Scheme 3: Electra, Park Avenue & Ninety-Eight ELC Electrical Diagram

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.

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 4)

Scheme 4

Scheme 4: Installation
Scheme 4: Installation

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 be removed to get drier out.

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.

AIR LINE REPAIR

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 5)

Scheme 5

Scheme 5: AIR LINE REPAIR
Scheme 5: AIR LINE REPAIR