1998 Mark 8 LSC collectors series car. Where is the air suspension control module?

1. NOTE: Air compressor and compressor air drier assembly is located ahead of the front RH wheel. It may be convenient to service the solid state compressor relay and the four air line connections by disassembling and carefully bending back the forward section of the RH front fender apron (16054).
3. Raise vehicle on hoist. Refer to Section 00-02 . Suspension must be in full rebound.
1. Remove wheel and tire assembly.
1. Remove RH front fender splash shield (16103).

If the engine seems to be running well, the problem is not likely with the thermostat, but with the blend door in the heater control box. These have a tendency to get stuck over time. To see if the have the potential for heat, warm the engine up to normal temperature. Then under the hood, find the heater hoses. They are smaller diameter hoses (about one inch in diameter). There are two of them one runs to the heater core, the other is the return line fell both hoses. If they are warm to the touch (almost hot), then you have coolant thru the core. If only one side is hot, then you may have a clogged heater core. If there is heat on both, the problem is in either the dash controls for the heat, of the blend box under the dash.

Your best bet take it an have it diagnosed ! This is computer controlled an may have DTC'S - diagnostic trouble codes stored !
C1724 Air Suspension Height Sensor Power Circuit Failure Air Suspension Control Module GO to Pinpoint Test F . C1726 Air Suspension Rear Pneumatic Failure Air Suspension Control Module GO to Pinpoint Test G . C1760 Air Suspension Rear Height Sensor High Signal Circuit Failure Air Suspension Control Module GO to Pinpoint Test H . C1770 Air Suspension Vent Solenoid Output Circuit Failure Air Suspension Control Module GO to Pinpoint Test I . C1790 Air Suspension LR Air Spring Solenoid Output Circuit Failure Air Suspension Control Module GO to Pinpoint Test J . C1795 Air Suspension RR Air Spring Solenoid Output Circuit Failure Air Suspension Control Module GO to Pinpoint Test K . C1830 Air Suspension Compressor Relay Circuit Failure Air Suspension Control Module GO to Pinpoint Test L
Symptom Chart Condition Possible Sources Action

• No communication with the air suspension control module

• CJB Fuse 4 (15A), 6 (5A) and 20 (5A).
• Circuitry.
• Air suspension control module.
• Air suspension switch.

• GO to Pinpoint Test A .

You replaced a part that you probably didn't need !

• The compressor is inoperative

• BJB Fuse 109 (50A).
• Air compressor assembly.
• Circuitry.
• Air suspension relay.

• GO to Pinpoint Test Q .

There is a lot to this system an guessing as to what the problem is ,isn't the way to fix it.
Measure the voltage between air compressor relay C1000 Pin A, Circuit 1053 (LB/PK), harness side and ground.

• Is the voltage greater than 10 volts?

Yes GO to Q3 .

No REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
Measure the resistance between air compressor C1000 Pin B, Circuit 538 (GY/RD), harness side and air compressor assembly C194M Pin 4, Circuit 538 (GY/RD), harness side.

• Is the resistance less than 5 ohms?

Yes GO to Q4 .

No REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
Air Suspension Height Sensor
One air suspension height sensor is mounted on the vehicle. The air suspension height sensor sends a voltage signal to the air suspension control module. The output ranges from approximately 4.75 volts at minimum height (when the vehicle is low or in full jounce), to 0.25 volts at maximum height (when the vehicle is high or in full rebound). The air suspension height sensor has a useable range of 80 mm (3.2 in) compared to total suspension travel of 200-250 mm (8 to 10 in) at the wheel. Therefore, the air suspension height sensor is mounted to the suspension at a point where full rear suspension travel at the wheel is relative to 80 mm (3.2 in) of travel at the air suspension height sensor. The air suspension height sensor is attached between the No. 5 frame crossmember (upper socket) and the panhard rod (lower socket). Replace the air suspension height sensor as a unit.
When the air suspension height sensor indicates that the rear of the vehicle is lower than trim under normal driving conditions, the air compressor will turn on and pump compressed air to the air springs. When the sensor indicates that the rear of the vehicle is raised above trim under normal driving conditions, this will cause the air to be vented from the air springs to lower the vehicle back to its trim height level.
Compressor Relay
The compressor relay is energized by the air suspension control module to allow high current to flow from the battery to the compressor motor.

• A solid state relay is used in the air suspension system for air compressor control. The relay incorporates a custom power metal oxide semi-conductor field effect transistor (MOSFET) and ceramic hybrid circuitry. The relay switches high current loads in response to low power signals and is controlled by the logic of the air suspension control module.
• Air Suspension Control Module
  NOTE: The 4WAS air suspension control module is used for the RAS system. The internal processor recognizes external circuitry to determine if it is installed in a 4WAS or a RAS equipped vehicle.
  NOTE: The air suspension control module is calibrated with information from the air suspension height sensor. A new or exchanged air suspension control module requires a ride height adjustment calibration process to be performed.
  The air suspension control module controls the air compressor motor (through a solid state relay), and the air spring solenoids. The air suspension control module also provides power to the air suspension height sensor. The air suspension control module controls vehicle height adjustments by monitoring the air suspension height sensor, vehicle speed, a steering sensor, acceleration input, the door ajar signal, transfer case signals, and the brake pedal position (BPP) switch. The air suspension control module also conducts all fail-safe and diagnostic strategies and contains self-test and communication software for testing the vehicle and related components.
  The air suspension control module monitors and controls the air suspension system through a 32-pin two-way connector. The air suspension control module is keyed so that the air suspension control module cannot be plugged into an incorrect harness. There are two sides of the harness connection to the air suspension control module. Each is uniquely colored and keyed to prevent reversing the connections.

Having it hooked up to a factory scan tool would be your best bet . Check for DTC'S diagnostic trouble codes . Without testing ,code scan ,we'd only be guessing .
Very complex , the untrained person hasn't got a pray of fixing this . You have no idea what your dealing with . Vehicle Dynamic Suspension The vehicle dynamic suspension consists of the following components:

• Rear air suspension control (RAS) module (5A919)
• Snorkel
• Drier
• Air compressor (5319)
• Air suspension switch (5K761)
• Solenoid valve (5311)
• Air spring (5560)
• Air suspension height sensor (5359)
• Air line
• Rear Air Suspension Control Module
  A microprocessor controls the air suspension system. The microprocessor and its supporting hardware are contained in the rear air suspension control module. The rear air suspension control module responds to signals from various sensors in the vehicle to maintain the programmed ride height while the vehicle is either moving or stopped. The rear air suspension control module accomplishes this by opening and closing solenoid valves to control the amount of air in the air spring(s). The rear air suspension control module turns on the compressor by applying voltage through the compressor relay to inflate the air spring(s) and raise the vehicle. The rear air suspension control module opens the vent solenoid to lower the vehicle by releasing air from the air spring(s) in response to signal inputs from the air suspension height sensor(s).
• Rear Air Suspension Control Module Diagnostic Trouble Code (DTC) Index DTC Description Source Action B1317 Battery Voltage High Rear Air Suspension Control Module GO to Pinpoint Test C . B1318 Battery Voltage Low Rear Air Suspension Control Module GO to Pinpoint Test C . B1342 ECU Is Defective Rear Air Suspension Control Module INSTALL a new rear air suspension control module. REFER to Module-Air Suspension Control . TEST the system for normal operation. C1441 Steering Sensor Channel A Circuit Failure Rear Air Suspension Control Module REFER to Section 211-00 . C1442 Steering Sensor Channel B Circuit Failure Rear Air Suspension Control Module REFER to Section 211-00 . C1722 Air Suspension Height Sensor Power Circuit Short to Power Rear Air Suspension Control Module GO to Pinpoint Test D . C1723 Air Suspension Height Sensor Power Circuit Short to Ground Rear Air Suspension Control Module GO to Pinpoint Test E . C1760 Air Suspension Rear Height Sensor High Signal Circuit Failure Rear Air Suspension Control Module GO to Pinpoint Test F . C1763 Air Suspension Rear Height Sensor High Signal Circuit Short to Ground Rear Air Suspension Control Module GO to Pinpoint Test G . C1765 Air Suspension Rear Height Sensor Low Signal Circuit Failure Rear Air Suspension Control Module GO to Pinpoint Test F . C1768 Air Suspension Rear Height Sensor Low Signal Circuit Short to Ground Rear Air Suspension Control Module GO to Pinpoint Test H . C1770 Air Suspension Vent Solenoid Output Circuit Failure Rear Air Suspension Control Module GO to Pinpoint Test I . C1773 Air Suspension Vent Solenoid Output Circuit Short to Ground Rear Air Suspension Control Module GO to Pinpoint Test J . C1790 Air Suspension LR Air Spring Solenoid Output Circuit Failure Rear Air Suspension Control Module GO to Pinpoint Test K . C1793 Air Suspension LR Air Spring Solenoid Output Circuit Short to Ground Rear Air Suspension Control Module GO to Pinpoint Test L . C1795 Air Suspension RR Air Spring Solenoid Output Circuit Failure Rear Air Suspension Control Module GO to Pinpoint Test M . C1798 Air Suspension RR Air Spring Solenoid Output Circuit Short to Ground Rear Air Suspension Control Module GO to Pinpoint Test N . C1813 Air Suspension Vent Request Exceeded Max Timing Rear Air Suspension Control Module GO to Pinpoint Test O . C1818 Air Suspension Air Compressor Request Exceeded Max Timing Rear Air Suspension Control Module GO to Pinpoint Test P . C1830 Air Compressor Relay Circuit Failure Rear Air Suspension Control Module GO to Pinpoint Test Q . C1832 Air Compressor Relay Circuit Short to Power Rear Air Suspension Control Module GO to Pinpoint Test R . C1840 Air Suspension Switch Circuit Failure Rear Air Suspension Control Module GO to Pinpoint Test S . C1842 Air Suspension Switch Circuit Short to Power Rear Air Suspension Control Module GO to Pinpoint Test D . C1897 Steering VAPS Circuit Loop Failure Rear Air Suspension Control Module REFER to Section 211-00 . U1041 SPC Invalid or Missing Data for Vehicle Speed

Hi Jose:
The first place to start is to have Ride Control Module scanned for trouble codes, this requires a high end scan tool. Most common problem is the air compressor in the rear or a height sensor. Here is how the system works.

Automatic Level Control Description and Operation
The RTD system is bi-state real time damping system. The Suspension Control module controls the suspension damper solenoids and suspension position sensors, along with parts of the automatic level control (ALC) system and electronic variable orifice (EVO) power steering system.

The Automatic Level Control system consists of the following:
• Suspension Control Module
• Compressor/Leveling Module
- Air Pressure Sensor
- Exhaust Solenoid
• Compressor Motor Relay

The objective of the Automatic Level Control System is to provide constant ride height at all load conditions. The Suspension Control module monitors body-to-wheel height, and vehicle speed.

The Suspension Control module will use the rear body-to-wheel displacements and vehicle speed inputs to keep the rear trim height of the vehicle at its desired level.

The electronic suspension control (ESC) system is bi-state real time damping system. The ESC module controls the suspension damper solenoids and suspension position sensors, along with parts of the automatic level control (ALC) system, if 1500 series.

The ESC system consists of the following:
• The ESC module
• The compressor/leveling module, if 1500 series
- The air pressure sensor, if 1500 series
- The exhaust solenoid, if 1500 series
• The compressor motor relay, if 1500 series
• The steering handwheel speed/position sensor
• The suspension damper solenoids
• The suspension position sensors

Hope this helps; also keep in mind that your feedback is important and I'll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using Fixya, and have a nice day.

Vehicle Dynamic Suspension The vehicle dynamic suspension consists of the following components:

• Rear air suspension control (RAS) module (5A919)
• Snorkel
• Drier
• Air compressor (5319)
• Air suspension switch (5K761)
• Solenoid valve (5311)
• Air spring (5560)
• Air suspension height sensor (5359)
• Air line

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Visual Inspection Chart Mechanical Electrical

• Restricted suspension movement
• Excessive vehicle load
• Cut, severed, or crimped air line(s)
• Damaged air spring(s)
• Height sensor damage
• Height sensor mounted incorrectly, disconnected, or damaged

• Central junction box (CJB):
  • Fuse 5 (15A)
• Battery junction box (BJB):
  • Fuse 8 (30A)
• Loose or corroded connectors
• Air suspension switch OFF

The air suspension control module is diagnosed using Super Star II Tester 418-F045 (007-0041B) or equivalent.
The test connector used to communicate with the air suspension control module is located on the RH side of the luggage compartment.
When the tester is connected, the engine is started and the HOLD/TEST button is latched down, the air suspension control module will respond sending a code 10 to the Super Star II Tester which represents "Diagnostics mode entered." If diagnostic trouble code (DTC) 10 is not displayed, go to Pinpoint Test A.
Air Suspension Control Module Diagnostic Trouble Code (DTC) Index
Condition Possible Sources Action

• No communication with the air suspension control module

• CJB Fuse 5 (15A).
• BJB Fuse 8 (30A).
• Circuitry.
• Air suspension control module.

• GO to Pinpoint Test A .

• Unable to enter auto test

• Air suspension control module.
• Circuitry.

• GO to Pinpoint Test B .

• Rear air suspension does not respond to load changes

• Circuitry.
• Air compressor.
• Air compressor inlet tube.
• Air compressor drier.
• Air suspension height sensor.
• Air suspension control module.

• GO to Pinpoint Test C .

• Rear rides low/high

• Circuitry.
• Air spring solenoid.
• Air suspension height sensor.
• Air suspension control module.

• GO to Pinpoint Test C .

• Poor ride quality

• Circuitry.
• Air springs.

• GO to Pinpoint Test C .

• Air suspension warning indicator ON

• Air suspension switch OFF.

• Place the air suspension switch in the ON position.

• Air suspension control module.
• Circuitry.

• GO to Auto Test.

• Instrument cluster (conventional cluster) or lamp warning module (electronic cluster).

• REFER to Section 413-01A (conventional cluster) or REFER to Section 413-01B (electronic cluster), or REFER to Section 413-01C (natural gas cluster).

Air Suspension Compressor Motor/Vent Solenoid : Lower RH front corner of engine compartment C134
Air Suspension Switch : Rear side of trunk C458
Air Suspension/EVO Steering Module : Behind RH cowl panel, above connector bracket C204, C205
Air Suspension/EVO Test Connector : RH side of engine compartment, top of wheel well C117 Soft Ride Relay : Under center front of package tray C403Hard Ride Relay : Under center rear of package tray C404 sorry could not find compressor rely listed, good luck

It has a cut off switch because you need to cut it off before jacking up the car or putting it on a lift.This keeps the air suspension from over inflating when jacking or lifting the car.Turn it back on . refer to owners manual

here's some info. Do you have a warning light on or does it say "Check Susp"?

Control Module
NOTE: The 4-wheel air suspension (4WAS) control module is also used for the rear air suspension (RAS) system. The internal processor recognizes external circuitry to determine if it is installed in a 4WAS or a RAS system.
NOTE: The air suspension control module is calibrated with information from the air suspension height sensors. A new or swapped air suspension control module requires the ride height adjustment calibration process to be performed.
A microcontroller-based electronic air suspension control module controls the air compressor motor (through a solid state relay), and all system solenoids. The air suspension control module also provides power to front and rear height sensors. The air suspension control module controls vehicle height adjustments by monitoring the two height sensors, vehicle speed, a steering sensor, acceleration input, the door ajar signal, transfer case signals, and the brake pedal position (BPP) switch. The air suspension control module also conducts all fail-safe and diagnostic strategies and contains self-test and communication software for testing of the vehicle and related components.
The air suspension control module is mounted in the passenger compartment inside the instrument panel, above the radio and temperature controls. The air suspension control module is interchangeable between the RAS and 4WAS system.
The air suspension control module monitors and controls the system through a 32-pin two-way connector. The air suspension control module is keyed so that it cannot be plugged into an incorrect harness. There are two sides of the harness connection to the air suspension control module. Each is uniquely colored and keyed to prevent reversing the connections.
Solenoid, Air Spring
WARNING: Never rotate an air spring solenoid valve to the release slot in the end cap fitting until all pressurized air has escaped from the spring to prevent damage or injury.
The air spring solenoid:

• Allows air to enter and exit the air spring during leveling operations.
• Is electrically operated and controlled by the air suspension control module.
• Is only replaced as a unit.

Air Suspension Diagnostic Connector
The air suspension diagnostic connector is used to aid the technician in diagnosing the air suspension system. It is also used to vent the system of compressed air when air suspension system components need to be repaired or replaced. The air suspension diagnostic connector is located under the steering column.
Steering Sensor
The steering sensor is mounted inside the passenger compartment on the steering column. It provides steering rate and position to the air suspension control module through two signals.
Pressure Relief Valve
The pressure relief valve (PRV) protects the rear air suspension components by venting the system to a specific pressure in the case of a system malfunction. The system will decrease the pressure to an acceptable level to maintain vehicle height. In the normal operation mode with normal system pressure the PRV is constantly closed and does not have any effect on the system performance or function. The PRV is replaceable without any air lines.
The PRV is located in the rear of the vehicle on the middle of crossmember #5 as a part of the rear air line assembly.

Experienced problem after problem with my suspension on my 1990 LSC. Finally contacted "Strut Masters" online and replaced my entire system with a conversion for less than 400 and an afternoon. Installation was simple.