Suspension - Electronic Level Control (with O Cvrss) Cadillac DeVille Concours I final

DESCRIPTION

Note. This article covers models equipped with Electronic Level Control (ELC) as a stand-alone system. For information on models that are equipped with both ELC and Continuously Variable Road-Sensing Suspension (CVRSS), see ELECTRONIC - LEVEL CONTROL - CADILLAC WITH CVRSS article.

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

SYSTEM OPERATION

When ride 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 about 13-27 seconds, height sensor grounds ELC relay, turning on compressor. Air is then pumped into struts, raising vehicle. Delay prevents system from operating during normal changes in ride 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 ELC relay, turning compressor off.

When ride 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 about 13-27 seconds, height sensor grounds exhaust solenoid valve circuit, causing air to be vented from struts, lowering vehicle. When vehicle has lowered 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, ELC 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 7 minutes. Time limit is necessary to prevent continuous compressor operation in case of air leak. 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, which extends when air pressure is increased in chamber.

Air Drier

Air drier, attached to compressor output, 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, located on right rear suspension support, provides air pressure for system operation. Compressor head casting contains intake and exhaust valves, and exhaust solenoid valve.

ELC Relay

ELC relay is located in trunk, below center of rear shelf. When ELC relay is grounded by height sensor, voltage is supplied to compressor.

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 rear underbody frame, links body to left rear suspension arm. Sensor controls ground circuits of ELC relay and exhaust solenoid valve.

1. Park vehicle on level surface. Ensure fuel tank is full and vehicle is unloaded. If necessary, simulate full tank by adding appropriate amount of weight to vehicle (about 7 lbs. for every gallon less than full). Ensure tire inflation pressure is correct. Move front seat rearward. Turn ignition on to activate ELC system. Bounce rear of vehicle 3 times to normalize suspension.
2. Measure rear ride height. See «REAR RIDE HEIGHT»(/cadillac/deville-concours/i-final-1999-1999/remont/electronic-suspension/#suspension-electronic-level-control-with-o-cvrss__rear-ride-height). If rear ride height varies by more than 1/2" (12 mm) from side to side, or is lower than specified, repair suspension problem before continuing procedure. If ride height is as specified, height sensor is adjusted.
3. If rear ride height is not within specification, loosen lock bolt on sensor arm. (Scheme 1) To increase ride height, move plastic arm upward. To decrease ride height, move plastic arm downward. Tighten lock nut.

Scheme 1

REAR RIDE HEIGHT

Mark a spot on bottom of rocker panel, 22 3/16" (563 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 7 9/16 - 8 11/32" (192-212 mm).

Scheme 2

SYSTEM OPERATION TEST

Note. Ensure height sensor arm assembly and link assembly are in good condition before performing system operation test.

1. Open hood and trunk. Turn ignition off. Place vehicle on flat surface. Measure distance from ground to top of rear wheelwell opening. This distance is unloaded height. Start engine. Cycle ignition off then on to reset system. Add 300 lbs. (136 kg) of weight to trunk. Allow at least 28 seconds for delay. If compressor starts, go to step 4 .
2. If compressor does not start and vehicle is within one inch (25.4 mm) of unloaded height, perform «SYSTEM DOES NOT EXHAUST»(/cadillac/deville-concours/i-final-1999-1999/remont/electronic-suspension/#suspension-electronic-level-control-with-o-cvrss__system-does-not-exhaust) test under SYMPTOM TESTS.
3. If compressor does not start and vehicle is not within one inch (25.4 mm) of unloaded height, perform «HEIGHT SENSOR»(/cadillac/deville-concours/i-final-1999-1999/remont/electronic-suspension/#suspension-electronic-level-control-with-o-cvrss) adjustment under ADJUSTMENTS, and then retest system. If compressor still does not operate after adjusting height sensor, perform «COMPRESSOR DOES NOT OPERATE»(/cadillac/deville-concours/i-final-1999-1999/remont/electronic-suspension/#suspension-electronic-level-control-with-o-cvrss__compressor-does-not-operate) test under SYMPTOM TESTS.
4. If compressor stops within 7 minutes, go to next step. If compressor runs continuously, check for the following conditions. If none of the following conditions exists, replace height sensor: Stuck ELC relay. Short to ground in Yellow wire between ELC relay and height sensor. Short to voltage in Dark Green wire between ELC relay and compressor connector.
5. If system leaks down, perform «IMPROPER OR CONTINUOUS EXHAUST»(/cadillac/deville-concours/i-final-1999-1999/remont/electronic-suspension/#suspension-electronic-level-control-with-o-cvrss__improper-or-continuous-exhaust) test under SYMPTOM TESTS. If vehicle returns to within one inch (25.4 mm) of unloaded height, remove load and go to next step. If vehicle does not return to within one inch (25.4 mm) of unloaded height, perform «HEIGHT SENSOR»(/cadillac/deville-concours/i-final-1999-1999/remont/electronic-suspension/#suspension-electronic-level-control-with-o-cvrss) adjustment under ADJUSTMENTS, and then retest system. If compressor still does not stop within 7 minutes, perform «IMPROPER OR CONTINUOUS EXHAUST»(/cadillac/deville-concours/i-final-1999-1999/remont/electronic-suspension/#suspension-electronic-level-control-with-o-cvrss__improper-or-continuous-exhaust) test under SYMPTOM TESTS.
6. If system exhausts within 28 seconds, go to next step. If system does not exhaust within 28 seconds, perform «SYSTEM DOES NOT EXHAUST»(/cadillac/deville-concours/i-final-1999-1999/remont/electronic-suspension/#suspension-electronic-level-control-with-o-cvrss__system-does-not-exhaust) test under SYMPTOM TESTS.
7. If vehicle returns to within one inch (25.4 mm) of unloaded height after 2 minutes of exhaust, system is operating correctly. If vehicle does not return to within one inch (25.4 mm) of unloaded height after 2 minutes of exhaust, adjust height sensor. See «HEIGHT SENSOR»(/cadillac/deville-concours/i-final-1999-1999/remont/electronic-suspension/#suspension-electronic-level-control-with-o-cvrss) under ADJUSTMENTS.

SYSTEM LEAK TEST

1. Install Pressure Gauge (J-22124-A) and Air Hose Set (J-22124-91) to air drier and rear struts. (Scheme 3) With shutoff valve open, apply shop air pressure through service valve on pressure gauge until pressure reaches 100-120 psi (7.0-8.4 kg/cm 2 ).
2. If a leak is indicated, close shutoff valve. This isolates compressor from rest of system. If air pressure continues to decrease, leak is external to compressor.
3. Test all connections using soapy water solution. Repair as necessary. If air pressure stops decreasing after shutoff valve is closed, leak is in compressor assembly. See «COMPRESSOR LEAK TEST»(/cadillac/deville-concours/i-final-1999-1999/remont/electronic-suspension/#suspension-electronic-level-control-with-o-cvrss__compressor-leak-test) under COMPONENT TESTS.
4. If air pressure increases rapidly but vehicle does not rise, check for pinched air line or stuck or binding rear struts.

Scheme 3

RESET CIRCUIT TEST

1. Turn ignition off. Disconnect height sensor connector. Measure voltage at Orange and Brown wire terminals of height sensor connector. If battery voltage is measured, repair short to battery voltage in Brown wire. If battery voltage is not measured, measure voltage at Orange wire terminal of height sensor connector.
2. If battery voltage is not measured, replace fuse and/or repair Orange wire. If battery voltage is measured, turn ignition on. Measure voltage at Brown wire terminal of height sensor connector. If battery voltage is not measured, replace fuse and/or repair Brown wire.
3. If battery voltage is measured, measure voltage between Orange and Black wire terminals of height sensor connector. If battery voltage is measured, replace height sensor. If battery voltage is not measured, repair open Black wire.

COMPRESSOR OPERATION TEST

Note. Compressor operation is checked by measuring 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)and (Scheme 5).
2. Disconnect compressor ground wire. Connect ammeter between ground wire and ground. At compressor connector, apply 12 volts to Dark Green wire terminal, and ground Black wire terminal. Note compressor motor current draw.
3. If compressor does not operate or current draw exceeds 10 amps, replace compressor assembly. If current draw is 10 amps or less, allow pressure to reach 100 psi (7.0 kg/cm 2 ), and then disconnect voltage supply.
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 drop, replace compressor head assembly.
5. If pressure completely leaks off, or if pressure does not increase to 100 psi (7.0 kg/cm 2 ), check compressor for leaks. See «COMPRESSOR LEAK TEST»(/cadillac/deville-concours/i-final-1999-1999/remont/electronic-suspension/#suspension-electronic-level-control-with-o-cvrss__compressor-leak-test). Remove pressure gauge.

Scheme 4

Scheme 5

COMPRESSOR LEAK TEST

1. Install Pressure Gauge (J-22124-A) to air drier. (Scheme 4)and (Scheme 5). With shutoff valve open, apply shop air pressure through service valve on pressure gauge until gauge reaches 100 psi (7.0 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 6)
3. If leak exists at cover bolts, tighten bolts in sequence to specification. (Scheme 9) See «TORQUE SPECIFICATIONS»(/cadillac/deville-concours/i-final-1999-1999/remont/electronic-suspension/#suspension-electronic-level-control-with-o-cvrss) table. Recheck compressor for leaks. Remove pressure gauge.

Scheme 6

HEIGHT SENSOR TEST

1. Raise and support vehicle. Ensure height sensor connector and ground wire connection are secure. Turn ignition off and then on to reset height sensor timing circuit. After delay of 35-45 seconds, compressor should run for about 4 seconds.
2. Disconnect link from height sensor metal arm. Move height sensor arm assembly upward. After delay of 13-27 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 delay of 13-27 seconds, struts should start to deflate. If system operates as described, height sensor is okay.

SYMPTOM TESTS

Note. For identification of connectors and terminals referenced in testing, see WIRING DIAGRAMS .

COMPRESSOR DOES NOT OPERATE

1. Ensure fuses are okay. Turn ignition on. Apply battery voltage across Dark Green and Black wire terminals of compressor connector. If compressor runs, go to next step. If compressor does not run, go to step 3 .
2. Disconnect height sensor connector. Turn ignition on. Connect jumper wire between Yellow and Black wire terminals of height sensor connector. If compressor runs, go to «RESET CIRCUIT TEST»(/cadillac/deville-concours/i-final-1999-1999/remont/electronic-suspension/#suspension-electronic-level-control-with-o-cvrss__reset-circuit-test) under SYSTEM TESTS. If compressor does not run, check for open Yellow wire or Black wire.
3. Remove ELC relay. Measure voltage at Orange wire terminal of ELC relay connector. If battery voltage is measured, go to next step. If battery voltage is not measured, check fuse. If fuse is okay, repair Orange wire.
4. Connect jumper wire between Orange and Dark Green wire terminals of ELC relay connector. If compressor does not run, go to next step. If compressor runs, check for open Yellow wire between ELC relay and height sensor. If Yellow wire is okay, replace ELC relay.
5. Disconnect compressor connector. Apply battery voltage to Dark Green wire terminal, and ground Black wire terminal of compressor connector. If compressor runs, repair open Dark Green wire or Black wire. If compressor does not run, replace compressor.

IMPROPER OR CONTINUOUS EXHAUST

Check for short to ground in White wire between compressor and height sensor. If wire is okay, perform COMPRESSOR OPERATION TEST under COMPONENT TESTS. If compressor is okay, perform SYSTEM LEAK TEST under SYSTEM TESTS. If no leaks are found, replace height sensor.

SYSTEM DOES NOT EXHAUST

1. Cycle ignition off then on to reset system. Disconnect compressor connector. Check for voltage at Orange wire terminal of compressor connector. If battery voltage is present, go to next step. If no voltage is present, check fuse. If fuse is okay, repair open Orange wire.
2. Reconnect compressor connector. Disconnect height sensor connector. Connect a jumper wire between White and Black wire terminals of height sensor connector.
3. If system exhausts, go to next step. If system does not exhaust, disconnect compressor connector. Apply 12 volts to Orange wire terminal, and ground White wire terminal of compressor connector. If system does not exhaust, replace exhaust solenoid. If system exhausts, repair open Orange wire or White wire.
4. Measure voltage at Orange wire terminal of height sensor connector. If battery voltage is not measured, repair open Orange wire. If battery voltage is measured, replace height sensor.

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 2 height sensor mounting screws. Remove height sensor. To install, reverse removal procedure. Tighten sensor mounting screws to specification. See TORQUE SPECIFICATIONS table. Adjust height sensor. See HEIGHT SENSOR under ADJUSTMENTS.

Removal

1. Raise vehicle on frame contact type hoist. Loosen exhaust pipes at both sides of muffler. Remove muffler heat shield. Disconnect compressor electrical connectors and air line from air drier.
2. Remove air inlet filter from underbody mount. Remove compressor bracket-to-suspension mounting screws. Move compressor and bracket toward rear of vehicle, and remove as an assembly. Remove bracket from 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 drier from compressor by turning spring clip 90 degrees and pulling drier and "O" ring from compressor head assembly. (Scheme 7)

Lubricate "O" ring and install in port of compressor head. Install 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. Install air tube to drier. Check system for leaks.

Scheme 7

1. Remove air drier assembly. See «AIR DRIER»(/cadillac/deville-concours/i-final-1999-1999/remont/electronic-suspension/#suspension-electronic-level-control-with-o-cvrss). Remove compressor head mounting bolts. Remove compressor head assembly. (Scheme 8)
2. To install, reverse removal procedure. Tighten compressor head bolts to specification and in sequence. (Scheme 9) See «TORQUE SPECIFICATIONS»(/cadillac/deville-concours/i-final-1999-1999/remont/electronic-suspension/#suspension-electronic-level-control-with-o-cvrss) table.

Scheme 8

Scheme 9

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

Electronic Level Control (ELC) System Wiring Diagram (DeVille & Eldorado - 1998). Scheme 10

Electronic Level Control (ELC) System Wiring Diagram (DeVille & Eldorado - 1999). Scheme 11

See also:
• REAR RIDE HEIGHT
• SYSTEM DOES NOT EXHAUST
• HEIGHT SENSOR
• COMPRESSOR DOES NOT OPERATE
• IMPROPER OR CONTINUOUS EXHAUST
• COMPRESSOR LEAK TEST
• RESET CIRCUIT TEST
• COMPRESSOR OPERATION TEST
• SYSTEM LEAK TEST