Suspension - Electronic Level Control Buick LeSabre VII

DESCRIPTION

Electronic Level Control (ELC) system automatically raises or lowers vehicle to correct riding height (curb height), compensating for loads added to or removed from vehicle. System consists of a compressor, air drier, exhaust (vent) solenoid, compressor relay, height sensor, air adjustable struts, pressure limiter and connecting air lines.

SYSTEM OPERATION

When riding height decreases due to weight being added to vehicle, height sensor arm assembly rotates upward in relation to height sensor. (Scheme 1) This activates a timing circuit in height sensor. After a delay of 17-27 seconds, height sensor grounds compressor relay, turning on compressor. Air is then pumped into struts, raising vehicle. Delay prevents system from operating during normal changes in riding height that occur during driving. As vehicle rises, height sensor rotates downward. When vehicle rises to within one inch (25.4 mm) of curb height, height sensor opens ground circuit to compressor relay, turning compressor off.

When riding height increases due to weight being removed from vehicle, height sensor arm assembly rotates downward. This activates the timing circuit in height sensor. After a delay of 17-27 seconds, height sensor grounds exhaust solenoid valve circuit, causing air to be vented from struts, lowering vehicle. When vehicle lowers to within one inch (25.4 mm) of curb height, height sensor opens exhaust solenoid valve circuit, causing exhaust solenoid valve to close.

To ensure system is operating with at least minimum air pressure, height sensor commands an air replenishment cycle each time ignition is turned on. An internal timer circuit is activated when ignition is turned on. After a delay of about 35-45 seconds, compressor turns on for 3-5 seconds to ensure residual system pressure exists. If weight is added to or removed from vehicle during 35-45 second delay, air replenishment cycle will be overridden and vehicle will rise or lower after normal time delay.

Voltage is applied to compressor, compressor relay, inflator timer and height sensor at all times. This allows system to vent if load is removed with ignition off. Height sensor limits compressor operation or exhaust solenoid energized time to about 4 1/2 and 7 1/2 minutes. Time limit is necessary to prevent continuous compressor operation in case of air leak or continuous exhaust solenoid operation. Turning ignition switch from OFF to ON position resets compressor operation or exhaust solenoid valve energized time.

Air Adjustable Struts

Air adjustable strut is a conventional strut enclosed in an air chamber that extends when air pressure in chamber increases.

Air Drier

Air drier, attached to compressor outlet, absorbs moisture from air being delivered to air adjustable struts. Air drier contains a valve that maintains a minimum air pressure of 7-14 psi (.49-.98 kg/cm 2 ) in struts.

Compressor

Compressor provides air pressure for system operation. Compressor head casting contains intake and exhaust valves, and exhaust valve solenoid. Compressor is located on left side of engine compartment.

Compressor Relay

When compressor relay is grounded by height sensor, voltage is supplied to compressor. Compressor relay is located near right kick panel, in relay center.

Exhaust Solenoid Valve

Exhaust solenoid valve, located in compressor head assembly, exhausts air from the system and limits compressor output pressure.

Height Sensor

Height sensor, mounted to underbody frame in rear of vehicle, links body to right rear suspension arm. Sensor controls ground circuits of compressor relay and exhaust solenoid valve.

HEIGHT SENSOR ADJUSTMENT

1. Park vehicle on level surface. Ensure fuel tank is full. If necessary, simulate full tank by adding about 7 lbs. (3.2 kg) of weight to rear of vehicle for each gallon of gas that is not in tank. Ensure vehicle is unloaded and tire inflation pressure is correct. Move front seats rearward. Turn ignition on to activate ELC system. Bounce rear of vehicle 3 times to normalize suspension.
2. Measure rear riding height. See «REAR RIDING HEIGHT ADJUSTMENT»(/buick/lesabre/vii-1992-1999/remont/electronic-suspension/#suspension-electronic-level-control__rear-riding-height-adjustment). If rear riding height varies by more than 3/4" (19 mm) from side to side or is lower than 9" (229 mm), repair suspension problem before continuing procedure. If rear riding height is within specification, height sensor is adjusted correctly.
3. If rear riding height is not within specification, loosen lock bolt on sensor arm. (Scheme 1) Move plastic arm upward or downward as necessary to increase or decrease rear riding height. To increase rear riding height, move plastic arm upward. To decrease rear riding height, move plastic arm downward. Tighten lock bolt.

Note. Height sensor can be adjusted a total of 5 degrees. One degree of change at height sensor results in a 1/4" (6 mm) change in height at rear bumper.

Scheme 1

REAR RIDING HEIGHT ADJUSTMENT

Mark a spot on bottom of rocker panel, 23 1/8 - 23 1/2" (590-600 mm) forward of rear axle center line (distance "A"). (Scheme 2) Measure distance between marked spot and ground (distance "B"). If vehicle is on hoist, consider ground line to be horizontal line between bottom of front and rear tires. Distance "B" should be as specified in REAR RIDING HEIGHT SPECIFICATIONS table.

REAR RIDING HEIGHT SPECIFICATIONS

Scheme 2

SYSTEM OPERATIONAL TEST

1. Ensure height sensor and link assembly are in good condition before performing system operation test. Place vehicle on flat surface. Measure distance from floor to rocker panel in front of rear wheelwell opening. (Scheme 2)
2. Turn ignition on. Add 300-350 lbs. (136-159 kg) of weight to rear of vehicle. After 17-27 second delay, compressor should turn on and vehicle should start to rise. Vehicle should rise to within 3/4 inch (19 mm) of measurement made in step 1).
3. Remove load from vehicle. After 17-27 second delay, vehicle should start to lower. Within 3 1/2 minutes, exhaust should stop and vehicle should be within 3/4 inch (19 mm) of measurement made in step 1). If ELC system does not function as specified, perform appropriate test under «ELECTRICAL TESTING»(/buick/lesabre/vii-1992-1999/remont/electronic-suspension/#suspension-electronic-level-control__electrical-testing).

SYSTEM LEAK TEST

1. Install Pressure Gauge (J-22124-A ) and Air Hose Set (J-22124-91 ) to air drier and struts. (Scheme 3) With shutoff valve open, apply shop air pressure through service valve on pressure gauge until pressure gauge reaches 100 psi (7.0 kg/cm 2 ).
2. If air leak is indicated, close shutoff valve. This isolates compressor from rest of system. Check for drop in air pressure. If air pressure continues to drop, leak is external to compressor.
3. Test all connections using soapy water solution and repair as necessary. If air pressure stops decreasing after shutoff valve is closed, leak is in compressor assembly. See «COMPRESSOR LEAK TEST»(/buick/lesabre/vii-1992-1999/remont/electronic-suspension/#suspension-electronic-level-control__compressor-leak-test) under COMPONENT TESTING.
4. If air pressure increases rapidly but vehicle does not rise, check for pinched air line and stuck or binding struts.

Scheme 3

AIR DRIER TEST

1. Disconnect air hose from air drier. If rear struts vent, go to next step. If rear struts do not vent, disconnect air hose from pressure limiter valve. If rear struts now vent, replace pressure limiter valve. If rear struts still do not vent, check for restricted air tube.
2. Reconnect air hose to air drier. Disconnect height sensor connector. Connect fused jumper wire between ground and Yellow wire of height sensor connector to run compressor for 2 minutes. Disconnect air drier from compressor head. If rear struts vent, replace compressor head. If rear struts do not vent, replace air drier.

COMPRESSOR OPERATION TEST

Note. Compressor operation test measures compressor current draw, compressor output and pressure leak-down.

1. Disconnect pressure line from air drier. Connect Pressure Gauge (J-22124-A ) to air drier. (Scheme 4) Disconnect compressor ground wire (Black wire) from compressor bracket and install ammeter between Black wire and ground.
2. Using a 12-volt battery, connect battery positive lead to Dark Green wire terminal, and battery negative lead to Black wire terminal of compressor connector. Note compressor motor current draw.
3. If compressor does not operate or current draw exceeds 14 amps, replace compressor assembly. If current draw is 14 amps or less, allow pressure to reach 100 psi (7.0 kg/cm 2 ) and disconnect voltage supply. NOTE: If compressor is allowed to run to maximum output pressure of 180 psi (12.7 kg/cm 2 ), solenoid exhaust valve will act as a relief valve. This gives a false indication of system leakage.
4. If pressure holds at 100 psi (7.0 kg/cm 2 ), compressor is okay. If pressure decreases to less than 60 psi (4.2 kg/cm 2 ), but does not continue to decrease, replace compressor head assembly.
5. If pressure completely leaks off, or builds up but does not reach 100 psi (7.0 kg/cm 2 ), check compressor for leaks. See «COMPRESSOR LEAK TEST»(/buick/lesabre/vii-1992-1999/remont/electronic-suspension/#suspension-electronic-level-control__compressor-leak-test).

Scheme 4

COMPRESSOR LEAK TEST

1. Install Pressure Gauge (J-22124-A ) to air drier so shutoff valve is on compressor side of gauge. (Scheme 4) With shutoff valve open, apply shop air pressure through service valve on pressure gauge until gauge reaches 100-120 psi (7.0-8.4 kg/cm 2 ).
2. Using soapy water solution, check for leaks around air drier cover, air drier "O" ring casting bore, edge of cover gasket, edge of solenoid valve housing, and head casting air intake and exhaust opening. (Scheme 5)
3. If leak exists at cover bolts, sequentially tighten bolts to specification. (Scheme 9) Recheck compressor for leaks. Remove pressure gauge

Scheme 5

COMPRESSOR RESIDUAL AIR TEST

1. Disconnect pressure line from air drier. Attach Air Pressure Gauge (J-22124-A ) to air drier fitting. Disconnect compressor relay wiring harness connector. Connect a jumper wire between battery positive terminal and Dark Green wire terminal to run compressor.
2. Allow pressure to reach 100 psi minimum (7.0 kg/cm 2 ), and then shut off compressor. Disconnect compressor wiring harness connector. Connect a jumper wire between battery positive terminal and White wire terminal. This causes system to exhaust.
3. When all air has been exhausted from system, air pressure gauge should register a residual amount of 7-14 psi (.49-.98 kg/cm 2 ). If there is no residual pressure, replace air drier cover and valve assembly.

HEIGHT SENSOR OPERATIONAL TEST

1. Turn ignition off and then on to reset height sensor timing circuit. Raise and support vehicle. Using jack stands, raise rear suspension arms until rear riding height is as specified. See «REAR RIDING HEIGHT ADJUSTMENT»(/buick/lesabre/vii-1992-1999/remont/electronic-suspension/#suspension-electronic-level-control__rear-riding-height-adjustment) under ADJUSTMENTS.
2. Disconnect link from height sensor metal arm. Ensure height sensor connector and ground wire connection are secure. Move height sensor arm assembly upward. After 17-27 seconds, compressor should turn on and struts should start to inflate.
3. As soon as struts start to inflate, move height sensor arm assembly downward until compressor stops. Continue to move height sensor arm assembly downward past area where compressor stopped. After 17-27 second delay, struts should start to deflate. If system operates as described, height sensor is okay.

ELECTRICAL TESTING

Note. Before performing electrical testing, ensure ELC system fuses are okay and link is attached to height sensor metal arm and lower control arm. After checking link, refer to following list of symptoms as a guide to determine which test or procedure to perform.

SYMPTOM-TO-TEST MENU

1. Compressor Does Not Operate Perform «COMPRESSOR RELAY & COMPRESSOR TEST»(/buick/lesabre/vii-1992-1999/remont/electronic-suspension/#suspension-electronic-level-control__compressor-relay-compressor-test) .
2. System Does Not Exhaust (Vehicle Does Not Lower) Perform «EXHAUST SOLENOID TEST»(/buick/lesabre/vii-1992-1999/remont/electronic-suspension/#suspension-electronic-level-control__exhaust-solenoid-test) .
3. Compressor Operates, But Vehicle Won't Reach Proper Height Perform «HEIGHT SENSOR TEST»(/buick/lesabre/vii-1992-1999/remont/electronic-suspension/#suspension-electronic-level-control__height-sensor-test) .
4. Compressor Cycles On & Off Frequently Perform «HEIGHT SENSOR TEST»(/buick/lesabre/vii-1992-1999/remont/electronic-suspension/#suspension-electronic-level-control__height-sensor-test) .
5. Compressor Operates For More Than 7 Minutes (Vehicle Stays At Maximum Height) Disconnect height sensor connector. If compressor stops, replace height sensor. If compressor does not stop, check for short to ground in Yellow wire between compressor relay and height sensor. If wire is okay, replace compressor relay.

COMPRESSOR RELAY & COMPRESSOR TEST

1. Disconnect height sensor connector. Connect jumper wire between ground and Yellow wire terminal of height sensor connector.
2. If compressor runs, perform «HEIGHT SENSOR TEST»(/buick/lesabre/vii-1992-1999/remont/electronic-suspension/#suspension-electronic-level-control__height-sensor-test) . If compressor does not run, disconnect compressor relay connector. Measure voltage at both Orange wire terminals of compressor relay connector. If battery voltage is not present, check for faulty Orange wires or fuse.
3. If battery voltage is present, cycle ignition off then on, check voltage between Orange wire terminal (No. 30) and Yellow wire terminal of compressor relay connector. Wait 35-45 seconds. If no voltage is present, perform «HEIGHT SENSOR TEST»(/buick/lesabre/vii-1992-1999/remont/electronic-suspension/#suspension-electronic-level-control__height-sensor-test) . If battery voltage is present for 3-5 seconds, go to next step.
4. Connect a fused jumper wire between Orange wire terminal (No. 30) and Yellow wire terminal of compressor relay connector. If compressor does not run, go to next step. If compressor runs, check for open Yellow wire. If wire is okay, replace compressor relay.
5. Leave fused jumper wire connected at compressor relay connector as in previous step. Disconnect compressor connector. Measure voltage at Dark Green wire terminal of compressor connector. If battery voltage is not present, check for open Dark Green wire.
6. If battery voltage is present, measure voltage between Dark Green and Black wire terminals of compressor connector. If battery voltage is not present, check for open Black wire. If battery voltage is present, check for poor connection at compressor connector. If connection is okay, perform «COMPRESSOR OPERATION TEST»(/buick/lesabre/vii-1992-1999/remont/electronic-suspension/#suspension-electronic-level-control__compressor-operation-test) under COMPONENT TESTING.

EXHAUST SOLENOID TEST

Note. Exhaust solenoid is an integral part of compressor head assembly. If exhaust solenoid is defective, replace compressor head assembly.

1. Disconnect height sensor connector. Momentarily ground Yellow wire terminal of height sensor connector to pressurize system. Connect fused jumper wire between ground and White wire terminal of height sensor connector. If exhaust solenoid clicks and air is vented, perform «HEIGHT SENSOR TEST»(/buick/lesabre/vii-1992-1999/remont/electronic-suspension/#suspension-electronic-level-control__height-sensor-test) .
2. If exhaust solenoid does not click and air is not vented, leave fused jumper wire connected. Disconnect compressor connector. Measure voltage at Orange wire terminal of compressor connector. If battery voltage is not present, repair open Orange wire.
3. If battery voltage is present, leave fused jumper wire connected as in previous step. Measure voltage between Orange and White wire terminals of compressor connector. If battery voltage is not present, repair open White wire. If battery voltage is present, check for poor connection at compressor connector. If connection is okay, perform «AIR DRIER TEST»(/buick/lesabre/vii-1992-1999/remont/electronic-suspension/#suspension-electronic-level-control__air-drier-test) under COMPONENT TESTING.

HEIGHT SENSOR TEST

1. Disconnect height sensor connector. Turn ignition switch to RUN position. Check height sensor power circuits. Refer to the «HEIGHT SENSOR VOLTAGE TEST»(/buick/lesabre/vii-1992-1999/remont/electronic-suspension/#suspension-electronic-level-control) table. Repair circuits if faulty.
2. If power circuits are okay, check for poor connection at height sensor connector. If connection is okay, reconnect height sensor connector. Turn ignition switch to OFF and then to RUN position. Wait 35-45 seconds. If compressor does not run, replace height sensor.
3. If compressor runs, raise and support vehicle. Ensure rear wheels are supported as close as possible to trim height specification. See «REAR RIDING HEIGHT ADJUSTMENT»(/buick/lesabre/vii-1992-1999/remont/electronic-suspension/#suspension-electronic-level-control__rear-riding-height-adjustment) under ADJUSTMENTS. Disconnect link from height sensor metal arm. Move height sensor arm assembly upward.
4. Allow 17-27 seconds for delay. If compressor does not run, replace the height sensor. If the compressor runs, but the struts do not inflate, perform «COMPRESSOR OPERATION TEST»(/buick/lesabre/vii-1992-1999/remont/electronic-suspension/#suspension-electronic-level-control__compressor-operation-test) under COMPONENT TESTING and the «SYSTEM LEAK TEST»(/buick/lesabre/vii-1992-1999/remont/electronic-suspension/#suspension-electronic-level-control__system-leak-test) under SYSTEM TESTING.
5. If compressor runs and struts inflate, slowly move height sensor arm assembly downward until compressor stops. If compressor does not stop, replace height sensor. If compressor stops, continue to move height sensor arm assembly downward.
6. Allow 17-27 seconds for delay. If struts do not deflate and vehicle does not lower, replace height sensor. If struts deflate and vehicle lowers, perform «HEIGHT SENSOR ADJUSTMENT»(/buick/lesabre/vii-1992-1999/remont/electronic-suspension/#suspension-electronic-level-control__height-sensor-adjustment) under ADJUSTMENTS.

HEIGHT SENSOR VOLTAGE TEST

VEHICLE LOADED, WILL NOT RISE

Check for leaks in air lines, fittings or struts, pinched lines between compressor and struts, defective height sensor, inoperative compressor, and loose or damaged electrical connections to sensor or compressor.

VEHICLE RISES WHEN LOADED, THEN LEAKS DOWN

Check for severe leak in lines, fittings or struts, and internal leak in compressor.

VEHICLE RISES PARTIALLY WHEN LOADED

Check for out-of-adjustment height sensor and defective compressor wiring.

VEHICLE RISES WHEN LOADED, LEAKS DOWN WHEN DRIVING

Check for defective drier or compressor, pinched air lines, and/or leaks in fittings or air lines.

VEHICLE RIDES HIGH

Check for out-of-adjustment height sensor, plugged air drier or pinched air lines, and poor electrical connections.

REMOVAL & INSTALLATION

Disconnect negative battery cable. Raise and support vehicle. Disconnect height sensor harness connector. Disconnect height sensor link from height sensor actuating arm. Remove height sensor screws. To install, reverse removal procedure. Tighten height sensor screws to specification. See TORQUE SPECIFICATIONS . Adjust height sensor. See HEIGHT SENSOR ADJUSTMENT under ADJUSTMENTS.

Removal

Disconnect negative battery cable. Disconnect compressor electrical connectors. Remove pressure limiter retaining clip from compressor bracket. Remove rear strut feed line from pressure limiter valve. Remove screws. Remove compressor-to-compressor 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.

Disconnect high pressure line by turning spring clip 90 degrees and removing tube assembly. Disconnect air drier from compressor by turning spring clip 90 degrees and pulling drier and "O" ring from compressor head assembly. (Scheme 6)

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

Scheme 6

AIR LINE REPAIR

Repair air line by splicing in a coupling at leak area. Inflate system to 100 psi (7.0 kg/cm 2 ). Use soap and water solution to locate leak. Deflate system through service valve, and cut out leaking area. Install coupling, and tighten tube nuts to 72 INCH lbs. (8 N.m). (Scheme 7) Inflate system. Check for leaks using soap and water solution.

Scheme 7

Remove air drier assembly. See AIR DRIER. Remove compressor head bolts. Remove compressor head assembly. (Scheme 8) To install, reverse removal procedure. Tighten compressor head bolts to specification and in sequence. (Scheme 9)

Scheme 8

Scheme 9

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

ELC System Schematic. Scheme 10

See also:
• COMPUTER RELEARN PROCEDURES
• REAR RIDING HEIGHT ADJUSTMENT
• REAR RIDING HEIGHT SPECIFICATIONS
• ELECTRICAL TESTING
• COMPRESSOR LEAK TEST
• COMPRESSOR RELAY & COMPRESSOR TEST
• EXHAUST SOLENOID TEST
• HEIGHT SENSOR TEST
• COMPRESSOR OPERATION TEST
• AIR DRIER TEST
• SYSTEM LEAK TEST
• HEIGHT SENSOR ADJUSTMENT