Suspension - Rear Electronic Level Control GMC Typhoon I

DESCRIPTION

Note. For any problems with abbreviations please see the ABBREVIATIONS article in the GENERAL INFORMATION Section.

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 and connecting air lines. Air drier contains a moisture absorbing chemical and pressure maintaining valves. Valves maintain minimum system pressure of approximately 7-14 psi (.5-.9 kg/cm 2 ).

On Lumina APV, Silhouette and Trans Sport, a provision is made so ELC compressor can be used for other purposes, such as inflating tires, etc. The inflation equipment consists of inflator switch, inflator solenoid valve assembly and inflation timer relay.

RAISING VEHICLE

When weight is added to vehicle, height sensor arm rotates upward, grounding compressor relay circuit. After a time delay of approximately 8-15 seconds, 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 8-15 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 is turned on. 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 rise or lower after normal time delay.

INFLATOR

On Lumina APV, Silhouette and Trans Sport, when inflator switch is turned on, it grounds the inflation timer relay. This operates the inflator solenoid valve assembly, turning on the compressor through the ELC relay. The inflator solenoid valve assembly redirects compressed air from the suspension to the inflator hose.

The inflation timer relay limits inflation operation to 10 minutes each time the inflator switch is operated.

HEIGHT SENSOR

1. Place vehicle on level surface, with gas tank full and NO load in vehicle. Turn ignition switch to ON position. Bounce vehicle 3 times to normalize suspension. To increase vehicle riding height, loosen lock bolt on sensor arm. Move plastic arm upward, and tighten lock nut.
2. To lower riding height, loosen lock nut, move plastic arm down and tighten lock nut. There is a total of 5 degrees adjustment on sensor. One degree adjustment provides 1/4" change in height at bumper. If adjustment cannot be made, problem is with rear springs or suspension. (Scheme 1)

Scheme 1

RIDING HEIGHT

Note. See RIDE HEIGHT in ALIGNMENT SPECIFICATIONS/PROCEDURES article in the WHEEL ALIGNMENT Section.

SYSTEM OPERATIONAL TEST

1. Unload vehicle. With ignition off, check riding height. Turn ignition on. Add 300 lbs. (136 kg) load to rear passenger compartment. Compressor should start operating after a time delay of approximately 8-15 seconds. Vehicle should rise to within 1" (25.4 mm) of curb height.
2. Remove load from passenger compartment. Exhaust should start within 8-15 seconds. Within 3 1/2 minutes, exhaust should stop and vehicle should be within 1" (25.4 mm) of curb height.

SYSTEM LEAK TEST

1. Install Pressure Gauge (J-22124-A ) in line between air drier assembly and existing line to shocks. (Scheme 2) Install gauge so shut-off valve is on compressor side of gauge. With shut-off valve open, apply shop air pressure through the fill valve until gauge 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 rise, check for pinched air line, and stuck air binding shocks.

Scheme 2

COMPRESSOR PERFORMANCE TEST

1. Disconnect pressure line from air drier and attach Pressure Gauge (J-22124-A ) to air drier fitting. Disconnect electrical connector 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. Replace compressor if current draw is greater than 14 amps. Allow pressure to reach 100 psi (7.03 kg/cm 2 ) minimum, and shut off compressor. Allow pressure to stabilize.
3. If pressure leaks down below 90 psi (6.33 kg/cm 2 ) before holding steady but does not reach zero psi, replace head assembly. If pressure leaks down to zero psi, perform compressor/drier leak test. Repair as necessary.
4. If compressor output is less than 110 psi (7.73 kg/cm 2 ), perform compressor/drier leak test. If no leak is found, replace compressor. See «COMPRESSOR/DRIER LEAK TEST»(/gmc/typhoon/i-1991-1993/remont/electronic-suspension/#suspension-rear-electronic-level-control__compressordrier-leak-test) under TESTING.
5. If compressor does not operate, replace compressor. If compressor operates correctly, reconnect wiring and air lines.

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.

COMPRESSOR/DRIER LEAK TEST

1. Attach Pressure Gauge (J-22124-A ) to drier fitting. Allow pressure to reach 100 psi (7.03 kg/cm 2 ) minimum and shut off compressor.
2. Using soap and water solution. Check for pressure leaks at locations shown. (Scheme 3) Torque compressor head bolts if necessary. See «TORQUE SPECIFICATIONS»(/gmc/typhoon/i-1991-1993/remont/electronic-suspension/#suspension-rear-electronic-level-control) table at end of article.

Scheme 3

HEIGHT SENSOR OPERATION TEST

1. To reset height sensor timer circuits, cycle ignition off, then on. Raise vehicle on hoist. Ensure rear 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. (Scheme 1) After an 8-15 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 actuator arm down.
3. Move sensor arm below position where compressor stopped running. There should be an 8-15 second delay before shock absorbers start to deflate, and lower vehicle. Replace height sensor if it does not function properly.

SENSOR ACTUATOR ARM TEST

Raise vehicle. Ensure link is attached to actuator arm correctly, and actuator arm is properly aligned. (Scheme 1)

Lumina APV, Silhouette & Trans Sport

1. Using digital volt/ohm meter (DVOM), measure voltage between inflation timer relay terminal "E" (Yellow wire) and ground. If voltage is not present, go to next step. If voltage measures battery voltage, go to step 6).
2. Measure voltage between ELC relay terminal No. 2 (Yellow wire) and ground. If voltage is not present, go to next step. If voltage measures battery voltage, repair open in circuit No. 321 (Yellow wire) between ELC relay and inflation timer relay.
3. Using test light, backprobe between ELC relay terminals No. 1 & 5 (Orange wires) and ground. If test light lights, go to next step. If test light does not light, repair open in circuit No. 340 (Orange wires) between ELC relay and fuse block.
4. Connect a fused jumper between ELC relay terminal No. 1 (Orange wire) and terminal No. 4 (Dark Green wire). If compressor motor starts, check for poor connections at ELC relay terminals No. 1 and No. 4. If connections are okay, replace ELC relay. If compressor motor does not start, with jumper still connected, disconnect compressor. Using test light, backprobe between body harness side of compressor terminal "B" (Dark Green wire) and ground. If test light lights, go to next step. If test light does not light, repair open in circuit No. 322 (Dark Green wire) between compressor and ELC relay.
5. With fused jumper connected as in step 4), connect test light to body harness side of compressor between terminal "B" (Dark Green wire) and terminal "D" (Black wire). If test light does not light, repair open in circuit No. 150 (Black wire) between compressor and ground. If test light lights, check for poor connections at compressor terminals "B" and "D". If connections are okay, replace compressor motor.
6. Using DVOM, measure voltage between inflation timer relay terminal "D" (Orange wire) and ground. If voltage measures battery voltage, go to next step. If voltage is not present, check for poor connection at inflation timer relay terminal "D", or for open in circuit No. 340 (Orange wire) between inflation timer relay and fuse.
7. Using DVOM, measure voltage between inflation timer relay terminal "D" (Orange wire) and terminal "H" (Black wire). If voltage is present, go to next step. If voltage is not present, repair open in circuit No. 150 (Black wire) between inflation timer relay and ground.
8. Disconnect inflator switch. Connect a fused jumper between inflator switch terminal "A" (White wire) and terminal "B" (Black wire). If compressor does not start, go to next step. If compressor motor starts, check for poor connections at inflator switch terminal "A" and "B". If connections are okay, replace inflator switch.
9. With fused jumper connected as in step 7), using DVOM, measure voltage between inflation timer relay terminal "F" (White wire) and ground. If voltage is not present, check for poor connections at inflation timer relay terminals "E" (Yellow wire), "F" (White wire) and "H" (Black wire). If connections are okay, replace inflation timer relay. If voltage measures battery voltage, check for open in circuit No. 1250 (White wire) or circuit No. 150 (Black wire) between inflation timer relay, inflator switch and ground.

1. Turn inflator switch to ON position. Using test light, backprobe between inflation timer relay terminal "C" (Dark Blue wire) and ground. If test light lights, go to next step. If test light does not light, check for poor connection at inflation timer relay terminal "C", or for open in circuit No. 340 (Orange wire). If connection and wire are okay, replace inflation timer relay.
2. Connect test light between inflator solenoid valve assembly terminal "A" (Dark Blue wire) and terminal "B" (Black wire). If test light does not light, check for open in circuit No. 1249 (Dark Blue wire) or circuit No. 150 (Black wire) between inflation timer relay, inflator solenoid valve assembly and ground. If test light lights, check for poor connections at inflator solenoid valve assembly terminals "A" and "B". If connections are okay, replace inflator solenoid valve assembly.

1. Disconnect inflation timer relay. Connect test light between inflation timer relay terminal "D" (Orange wire) and terminal "A" (Purple wire). Press and hold inflator switch to OFF position.
2. If test light does not light, check for poor connection at inflator switch terminal "C" (purple wire), or for open in circuit No. 1267 (Purple wire). If connection and wire are okay, replace inflator switch.
3. If test light lights, check for poor connection at inflation timer relay terminal "A" (Purple wire). If connection is okay, replace inflation timer relay.

1. Disconnect height sensor. Connect a fused jumper to body harness side of height sensor between terminal "B" (Yellow wire) and ground. If compressor motor starts, go to next step. If compressor motor does not start, repair open in circuit No. 321 (Yellow wire).
2. Remove jumper. Using test light, probe body harness side of height sensor between terminal "C" (Light Blue wire) and ground. If test light lights, go to next step. If test light does not light, check for poor connection at inflation timer relay terminal "B" (Light Blue wire), or for open in circuit No. 1248 (Light Blue wire). If connection and wire are okay, replace inflation timer relay.
3. Using test light, probe body harness side of height sensor between terminal "C" (Light Blue wire) and terminal "A" (Black wire). If test light does not light, repair open in circuit No. 150 (Black wire) between height sensor and ground. If test light lights, turn ignition to "RUN" position and probe body harness side of height sensor between terminal "D" (Pink/Black wire) and ground.
4. If test light does not light, check for poor connection at height sensor terminal "D" (Pink/Black wire), connector C200 terminal D1 (Pink/Black wire), connector C302 terminal "D" (Pink/Black wire) or for open in circuit No. 39 (Pink/Black wire) between height sensor and fuse block. If test light lights, check for poor connection at height sensor terminal "D" (Pink/Black wire), or actuator arm for damage or binding. Also, check height sensor adjustment. If all checks are okay, replace height sensor.

Typhoon

1. Disconnect height sensor. Connect a fused jumper to body harness side of height sensor between terminal "B" (Yellow wire) and ground. If compressor motor starts, go to next step. If compressor motor does not start, repair open in circuit No. 321 (Yellow wire).
2. Remove jumper. Using test light, probe body harness side of height sensor between terminal "C" (Orange wire) and ground. If test light lights, go to next step. If test light does not light, check for poor connection at connector C112, or for open in circuit No. 340 (Orange wire).
3. Using test light, probe body harness side of height sensor between terminal "C" (Orange wire) and terminal "A" (Black wire). If test light does not light, repair open in circuit No. 150 (Black wire) between height sensor and ground. If test light lights, turn ignition to "RUN" position and probe body harness side of height sensor between terminal "D" (Pink wire) and ground.
4. If test light does not light, check for open in circuit No. 39 (Pink wire) between height sensor and connector C112. If test light lights, check for poor connection at height sensor terminal "D" (Pink wire), or actuator arm for damage or binding. Also, check height sensor adjustment. If all checks are okay, replace height sensor.

ELECTRONIC LEVEL CONTROL SYSTEM DOES NOT VENT TO LOWER REAR OF VEHICLE

1. Disconnect height sensor. Connect a fused jumper to body harness side of height sensor between terminal "E" (White wire) and ground. Vent solenoid should click and vent air. If vent solenoid does not operate, go to next step. If vent solenoid operates, check for poor connection at height sensor terminal "E", or actuator arm for damage or binding. Also, check height sensor adjustment. If all checks are okay, replace height sensor.
2. Does fuse in fused jumper blow? If fuse blows, repair short to voltage on circuit No. 320 (White wire). If fuse does not blow, with jumper still connected, disconnect compressor assembly. Connect test light to body harness side of compressor assembly between terminal "C" (Orange wire) and terminal "A" (White wire).
3. If test light lights, check for poor connections at compressor assembly terminals "A" and "C". If connections are okay, replace vent solenoid. If test light does not light, check for open in circuit No. 340 (Orange wire) or No. 320 (White wire).

COMPRESSOR MOTOR RUNS CONTINUOUSLY OR FOR MAXIMUM RUN TIME, THEN STOPS

1. Turn ignition switch to OFF position. Disconnect compressor assembly and height sensor. Connect test light to body harness side of height sensor between terminal "E" (White wire) and battery voltage. If test light does not light, go to next step. If test light lights, repair short to ground in circuit No. 320 (White wire).
2. Reconnect height sensor. Connect test light to body harness side of compressor assembly between terminal "A" (White wire) and battery voltage. If test light lights, replace height sensor. If test light does not light, check electronic level control system for air leaks. Also, check height sensor adjustment. If all checks are okay, replace vent solenoid.

TROUBLE SHOOTING

Perform SYSTEM OPERATIONAL TEST and SYSTEM LEAK TEST under TESTING to determine if electrical fault exists. Refer to WIRING DIAGRAMS and ELC COMPONENT LOCATION , ELC CONNECTOR LOCATION and ELC CIRCUIT IDENTIFICATION tables to locate and identify circuits, components, etc.

VEHICLE 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.

VEHICLE LOADED, RISES, THEN LEAKS DOWN

Severe leak in lines, fittings or shock absorbers. Internal leak in motor.

VEHICLE LOADED, RISES PARTIALLY

Height sensor out of adjustment. Compressor or wiring defective.

VEHICLE RISES WHEN LOADED, LEAKS DOWN WHEN DRIVING

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

VEHICLE RIDES HIGH

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

ELC COMPONENT LOCATION

ELC CONNECTOR LOCATION

ELC CIRCUIT IDENTIFICATION

REMOVAL & INSTALLATION

Disconnect battery negative cable. Raise and support vehicle. Disconnect height sensor electrical connector. Disconnect height sensor link from height sensor actuator arm. Remove height sensor mounting screws and remove height sensor. To install, reverse removal procedure. Adjust height sensor. See HEIGHT SENSOR under ADJUSTMENTS. Tighten sensor mounting screws to specification. See TORQUE SPECIFICATIONS table at end of article.

Removal

1. Disconnect battery negative cable. Raise and support vehicle. Remove compressor shield. Deflate system through service valve. Disconnect high pressure line at air drier by rotating spring 90 degrees while holding connector end. Remove tube assembly. (Scheme 4)
2. Disconnect electrical connectors. Remove compressor mounting bolts, nuts and washers. Remove compressor.

Installation

To install, reverse removal procedure. Tighten bolts to specification. See TORQUE SPECIFICATIONS table at end of article. Turn ignition on and allow system to cycle. Check for leaks using soap and water solution.

Scheme 4

Disconnect battery negative cable. Raise and support vehicle. Remove bolts retaining air drier and bracket to compressor. Disconnect air drier from compressor by rotating spring 90 degrees. Remove air drier.

Lubricate "O" ring and install in port of compressor head. Return 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 apply pressure. Check system for leaks.

AIR LINE REPAIR

If a leak is found in air line, it is not necessary to replace entire line. Air line can be repaired by splicing in a service 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 service coupling and tighten tube nuts to 72 INCH lbs. (8 N.m). (Scheme 5) Inflate system and check for leaks using a soap and water solution.

Scheme 5

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

Electronic Level Control (ELC) Wiring Diagram (Lumina APV, Silhouette & Trans Sport). Scheme 6

Electronic Level Control (ELC) Wiring Diagram (Typhoon). Scheme 7

See also:
• COMPRESSOR/DRIER LEAK TEST
• TORQUE SPECIFICATIONS
• SYSTEM OPERATIONAL TEST
• SYSTEM LEAK TEST
• HEIGHT SENSOR