Bonneville Automatic Load-Leveling System

[bholthaus]

Hey,

I have a 96 SSE and the air pump in the load leveing system won't turn on. I have looked all over for a wiring schematic etc and have found nothing. I want to troubleshoot the system, but have nowhere to start. I was thinking of starting at the air pump, but don't know which wires to supply voltage to. Please help if anybody can. The system dosen't work, I have checked and found 2 fuses in the driver side box and a relay clicks when I press the on button for the air in the trunk, but thats all.

Thanks in advance for any help

Brad

[randman1]

First, some technical information:

Description and Operation

CIRCUIT OPERATION

The electronic level control (ELC) keeps the rear of the vehicle at a constant height. If weight is added to the vehicle, the ELC height sensor turns on the ELC compressor. Air is pumped into the rear struts until the vehicle is level.

An actuator arm is connected between the rear axle control and the ELC height sensor, which is mounted on the body. It turns as the vehicle height changes. A solid state unit detects this motion and operates switches to control the air flow into and out of the rear struts.

Voltage is applied at all times to the ELC height sensor, ELC relay, ELC compressor assembly vent solenoid and inflator timer-relay. This allows the ELC system to lower the vehicle height with the ignition switch in OFF. Voltage is applied to terminal D of the ELC height sensor only with the ignition switch in RUN. The compressor, after an initial delay, will run for a few seconds to charge the system when the ignition switch is turned to RUN.

The ELC height sensor delays 17 to 27 seconds after a change in vehicle height before closing switch C in the ELC height sensor. This prevents system operation during normal ride motions. In addition, the ELC height sensor limits compressor run time or vent solenoid energized time to a maximum of 10 minutes.

This time limit is necessary to prevent continuous compressor operation in case of a severe system leak or continuous vent. Turning the ignition switch OFF and ON resets the 10 minutes maximum run time.

Raising the Vehicle
When a load is added to the vehicle, the vehicle body is moved downward and the actuator arm rotates upward. Switch B closes in the ELC height sensor. After a 17-27 second delay, switch C closes. The coil in the ELC relay is energized and the relay contacts close. Battery voltage is applied to the compressor motor. The compressor operates and pumps air into the adjustable rear struts. As the struts inflate, the vehicle body moves upward. When the actuator arm rotates back to its original position (plus or minus 1 inch), switch B opens, the relay is no longer energized and the compressor stops.

Lowering the Vehicle
When a load is removed from the vehicle, the vehicle body is moved upward and the actuator arm rotates downward. After a 17 to 27 second delay, switch C closes, the vent solenoid is energized and air is exhausted from the rear struts. As the vehicle body moves downward, the actuator arm is rotated back to its original position (plus or minus 1 inch), switch A opens and the vent is no longer energized.

Inflator
When air is needed to fill a tire, connecting the inflator hose and then turning the inflator switch to ON activates the inflator solenoid valve and ELC compressor. The ELC compressor pumps and air is diverted from the ELC system to the inflator system by the inflator solenoid valve.
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To answer your specific question, DK GRN (pin B) is the +12v from the ELC relay and BLK (pin D) is the ground. WHI (pin C) is the exhaust signal and ORN (pin A) is +12v for the exhaust solenoid. This info is from my 93 so the colors may be different. The pin locations may be more accurate.

The ELC relay and the exhaust solenoid are supplied by IP fuse #12. The ELC sensor is supplied by IP fuse #17

[bholthaus]

Okay,

I checked and have voltage at the orange wire just like you said. I tried to turn on the trunk inflator and voltage at orange was constant, and there was no voltage at the dark green wire. I unhooked the ELC sensor from the frame and manipulated it to max load waited for at least 1 minute and there was no change in voltage for either orange or dk green wire. I had the same results with the min load situation. I guess the next step is to troubleshoot the ELC height sensor to see if it is functioning properly. I would really appreicate any advise on that. Thanks so much for the information that you have provided me thus far. Also if you know what amperage the air pump operates at I could run an alternate power source to the pump just to see if it operates properly. I don't want to overload the pump with a non-fused source.

Thanks again in advance.

Brad

[randman1]

Constant voltage on the orange wire indicates that the fuse is good and we can assume that the voltage to the ELC relay is OK cause it's the came circuit. The compressor is protected with a 20 amp fuse. For your testing, I'd suggest a 15 or even 10 amp because that will be the only draw.

According to the 93 diagram, there is a yellow wire (pin B) from the height sensor that activates the ELC relay. Ground this wire and verify +12v at the DK GRN wire. The compressor should start. If it does, the height sensor is suspect.

It might be easier for you to peek at what I'm looking at. Send me a Private Message with your email address.

[BONZD67]

I realize this is an old thread. However, I am having some issues with my wife's Bonneville. My issue seems to be the complete opposite of everything I have found.

I cannot get the ELC to move the vehicle DOWN. I have removed both fuses from the box underneath the rear seat, and even tried removing both independently from each other. The compressor does not run whatsoever, but the vehicle remains "jacked up" in the back.

I have tried putting weight on the rear suspension and removing it numerous times, but to no avail. Any ideas?