Question about 1998 Cadillac DeVille

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Ttrying to fine out where to put the air for the airshock

They said that i could put air in my airshocks like i do my tires but i dont know where it goes. Can you please help me

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Vehicles: Cadillacs with ALC-controlled rear shock absorbers

Each rear shock absorber has an ALC (air) port. One may disconnect the ALC air line and try to add air, but this is unlikely to work, since there is no spring-loaded valve to close the port off immediately (like a tire).

A better method for inflating the rear shocks to see if they hold air is to supply 12V DC (from the battery) directly to the ALC system (air) compressor.

Debugging your Cadillac's ALC system can be a challenge. Here are a few basics.

Here's a depiction of the ALC port on the rear shock - found at the end of the ALC air tube.


ttrying to fine out where to put the air for the a - 12_2_2011_12_54_42_am.jpg

Fig. 1 The ALC connection on the rear shock absorber

Here's a close-up of the Cadillac ALC port on the rear shock


12_2_2011_12_59_49_am.jpg

Fig.2 Cadillac ALC air line fitting

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Automatic Level Control System - General Description
Vehicles Without Road Sensing Suspension

The Automatic Level Control (ALC) system automatically adjusts the rear height of the vehicle in response to changes in vehicle loading.

The ALC system consists of a height sensor, an air compressor assembly, an ALC compressor relay, an intake hose and filter, an air tube, and two rear shock absorbers . The air compressor assembly consists of an air compressor and an air dryer mounted on a bracket. The air compressor head is a replaceable part of the air compressor. The (air) exhaust solenoid is a non-replaceable part of the air compressor head.

The compressor is activated when the ignition is on, and weight is added to the vehicle. The exhaust solenoid is connected directly to the battery (+), enabling the system to exhaust with the ignition on or off when excess weight is removed.

Vehicles With Road Sensing Suspension
The Automatic Level Control (ALC) system automatically adjusts the rear height of the vehicle in response to changes in vehicle loading.

The ALC system consists of the CVRSS control module, two CVRSS position sensors, an air compressor assembly, an ALC compressor relay, an intake hose and filter, an air tube, and two rear shock absorbers. The air compressor assembly consists of an air compressor and an air dryer mounted on a bracket. The air compressor head is a replaceable part of the air compressor. The exhaust solenoid is a non-replaceable part of the air compressor head.

The vehicles rear vertical height is measured by the two CVRSS position sensors. These two position sensors convert this rear height measurement into an analog voltage (0 to 5 volts DC) which is read by the CVRSS control module. The control module then determines what action (exhaust, compress, or no action) shall take place. To compress, the CVRSS control module switches the low-side of the ELC compressor relay to ground.

The air compressor is enabled (switched to battery only when the ignition is on. The air compressor is activated when a sufficient amount of weight has been added to the vehicle.

The exhaust solenoid is enabled at all times. The exhaust solenoid is activated when weight is removed from the vehicle.

Automatic Level Control System Operation w/o F45

Raising the Vehicle
When a load is added to the vehicle, the vehicle body moves down causing the sensor actuating arm to rotate upward. The upward arm movement activates an internal timing circuit and, after an initial fixed delay of 17 to 27 seconds, the sensor provides a ground to complete the compressor relay circuit. The 12V (+) circuit to the compressor is then complete and the compressor runs, sending pressurized air to the shock absorbers through the air tubes.

As the shock absorbers inflate, the vehicle body moves upward rotating the actuating arm towards its original position. Once the body reaches its original height, +/- 25 mm (+/- 1 in), the sensor opens the compressor relay circuit, and the compressor is turned off.

Air Compressor Head Relief Sequence
In order to reduce current draw during air compressor starting, the height sensor performs an air compressor head relief sequence before air compressor operation. This sequence reduces the air pressure in the air compressor cylinder during start-up. The air compressor head relief sequence occurs as follows:

Exhaust solenoid is energized.
Air compressor is activated 1.3 seconds after the exhaust solenoid is energized.
Exhaust solenoid is de-energized 0.5 seconds after the air compressor is activated.
Lowering the Vehicle
When a load is removed from the rear of the vehicle, the body rises, causing the sensor actuating arm to rotate downward. This again activates the internal timing circuit. After the initial fixed delay, the sensor provides a ground to complete the exhaust solenoid circuit, energizing the solenoid. Now, air starts exhausting out of the shock absorbers, back through the air dryer and exhaust solenoid valve, and into the atmosphere.

As the vehicle body lowers, the actuating arm rotates to its original position. When the vehicle body reaches its original height, +/- 25 mm (+/- 1 in), the sensor opens the exhaust solenoid circuit, which closes the exhaust solenoid and prevents air from escaping.

Air Replenishment Cycle
The sensor actuating arm position is checked when the ignition is turned on. If the sensor indicates that no height adjustment is needed, an internal timer circuit is activated. After about 35 to 55 seconds, the compressor is turned on for 3 to 5 seconds. This ensures that the shock absorbers are filled with the proper residual pressure. If weight is added to or removed from the vehicle during the time delay, the air replenishment cycle is overridden, and the vehicle rises or lowers after the normal delay.

Automatic Level Control System Operation w/ F45

Raising the Vehicle
When a load is added to the vehicle, the vehicle body moves down causing the sensor actuating arm to rotate upward. The upward arm movement activates an internal timing circuit and, after an initial fixed delay, the CVRSS control module provides a ground to complete the compressor relay circuit. The 12V (+) circuit to the compressor is then complete and the compressor runs, sending pressurized air to the shock absorbers through the air tubes.

As the shock absorbers inflate, the vehicle body moves upward rotating the actuating arm towards its original position. Once the body reaches its original height, +/- 25 mm (+/- 1 in), the compressor relay circuit is opened and the compressor is turned off.

Air Compressor Head Relief Sequence
In order to reduce current draw during air compressor starting, the CVRSS control module performs an air compressor head relief sequence before air compressor operation. This sequence reduces the air pressure in the air compressor cylinder during start-up. The air compressor head relief sequence occurs as follows:

Exhaust solenoid is energized.
Air compressor is activated 1.3 seconds after the exhaust solenoid is energized.
Exhaust solenoid is de-energized 0.5 seconds after the air compressor is activated.

Lowering the Vehicle
When a load is removed from the rear of the vehicle, the body rises, causing the sensor actuating arm to rotate downward. This again activates the internal timing circuit. After the initial fixed delay, the CVRSS control module provides a ground to complete the exhaust solenoid circuit, energizing the solenoid. Now, air starts exhausting out of the shock absorbers, back through the air dryer and exhaust solenoid valve, and into the atmosphere.

As the vehicle body lowers, the actuating arm rotates to its original position. When the vehicle body reaches its original height, +/- 25 mm (+/- 1 in), the exhaust solenoid circuit is opened, which closes the exhaust solenoid and prevents air from escaping.

Air Replenishment Cycle
An air replenishment cycle (ARC) is commanded after each ignition-ON cycle. The purpose of the ARC is to ensure that the ALC system is operating at or above minimum air pressure (residual air pressure). The ARC occurs as follows:

The EXHAUST SOLENOID IS ENERGIZED 20 seconds after the ignition has been turned on.
The AIR COMPRESSOR IS ACTIVATED 1.3 seconds after the exhaust solenoid is energized.
The EXHAUST SOLENOID IS DE-ENERGIZED 0.5 seconds after the air compressor is activated.
The AIR COMPRESSOR IS DEACTIVATED 3.2 seconds after the exhaust solenoid is de-energized.

Posted on Dec 02, 2011

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