WHERE IS THE REAR HEIGHT SENSOR ON 2004 LINCOLN NAVIGATOR

Have to restart what ? Vehicle ? Did you have the system check for code's ?
The four wheel air suspension system is comprised of the following components:

• Service switch
• Control module
• Two front height sensors
• One rear height sensor
• Compressor and drier assembly (includes vent solenoid)
• Air lines
• Front and rear air spring and shock absorber assemblies
• Four air spring solenoids
• Compressor relay
• Vehicle Dynamic Module (VDM) Diagnostic Trouble Code (DTC) Index NOTE: Repair all other DTCs before C1725 and C1726. Repair DTCs C1990 and C1991 last. DTCs Description Source Action B1317 Battery voltage high VDM Go To Pinpoint Test C . B1318 Battery voltage low VDM Go To Pinpoint Test C . B1342 ECU is defective VDM INSTALL a new VDM. REFER to Air Suspension Control Module in this section. SET the ride height. REFER to Ride Height Adjustments in this section. CARRY OUT the pneumatic test. TEST the system for normal operation. B2477 VAPS II steering assist curve not complete VDM REFER to Section 211-00 . C1445 Vehicle speed signal circuit failure VDM GO to Symptom Chart . C1724 Air suspension height sensor power circuit failure VDM Go To Pinpoint Test D . C1725 Air suspension front pneumatic failure VDM Go To Pinpoint Test E . C1726 Air suspension rear pneumatic failure VDM Go To Pinpoint Test E . C1760 Air suspension rear height sensor signal circuit failure VDM Go To Pinpoint Test F . C1770 Air suspension vent solenoid output circuit failure VDM Go To Pinpoint Test G . C1790 Air suspension LR air spring/shock solenoid output circuit failure VDM Go To Pinpoint Test H . C1795 Air suspension RR air spring/shock solenoid output circuit failure VDM Go To Pinpoint Test H . C1830 Air suspension compressor relay circuit failure VDM Go To Pinpoint Test I . C1840 Air suspension disable switch circuit failure VDM Go To Pinpoint Test J . C1873 Air suspension RF air spring solenoid output circuit failure VDM Go To Pinpoint Test H . C1877 Air suspension LF air spring solenoid output circuit failure VDM Go To Pinpoint Test H . C1881 Air suspension RF height sensor circuit failure VDM Go To Pinpoint Test F . C1889 Air suspension LF height sensor circuit failure VDM Go To Pinpoint Test F . C1897 Steering VAPS circuit loop failure VDM REFER to Section 211-00 . C1964 Air suspension compressor actual run time exceeded allowed run time VDM Allow the air compressor to cool down. CLEAR the DTC. REPEAT the self-test. C1990 New control module initialization (requires ride height calibration and pneumatic test pass) VDM REFER to "Clearing DTC C1990 or C1991". C1991 Plant ride height setting and/or tests incomplete VDM REFER to "Clearing DTC C1990 or C1991".

Ford Air Ride Rear Suspension Down Diagnosis & Fix ...

? 9:57
https://www.youtube.com/watch?v=wfh7n17hvN8
Feb 24, 2014 - Uploaded by FordTechMakuloco
Ford Air Ride Rear Suspension Down Diagnosis & Fix ... why theair ride compressor is not turning on and pumping up the air ridesuspension on your truck. ... Ford Expedition & Lincoln Navigator Air Ride C1725 Common Faults ... 2000 Ford Expedition - Replacing the rear shocks with load leveling shocks ...

2003 Lincoln Navigator air suspension fix(3) - YouTube

? 3:41
https://www.youtube.com/watch?v=MhWlcYycny4

If it is easy to remove the sensor and the plugs are the same. I would try that. That will tell you if the sensor is bad(the rear will inflate). Or if it is the module. (It won't inflate).

Have you checked the height sensor ?

Bad height sensor or air suspension compressor has died? If you hear the pump, then it might be the sensors. If there's nothing, could be a blown fuse or the system was swtiched off (switch in the trunk)

Try this.... My 2003 Lincoln Navigator was manufactured May 22, 2003 so it's the late model that came with the Intec 5.4 Liter DOHC V-8 (not the Triton engine). I replaced the two front ride height sensors (one for each air strut) and replaced the one rear ride height sensor (passenger side) that controls the ride height for BOTH rear air struts. That solved the problem for a few months during warm weather, until the weather started cooling off. Then back to the same issue. The front passenger air strut started releasing air from the solenoid (air block) making a "hissing sound." Replaced BOTH front air strut solenoids (connected at the top of each air strut). That also resolved the problem for a few days. After going all around the world, I discovered it's the Air Ride Control Module (ASM) that was the problem all along.

This is most likely the culprit for your air ride suspension problem.

Vehicle Dynamic Suspension The four wheel air suspension system is comprised of the following components:

• service switch
• control module
• two front height sensors
• one rear height sensor
• compressor and drier assembly (includes vent solenoid)
• air lines
• front and rear air spring and shock absorber assemblies
• four air spring solenoids

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Visual Inspection Chart Mechanical Electrical

• Restricted suspension movement
• Excessive vehicle load
• Cut, severed, crimped air line(s)
• Unmounted height sensor(s)
• Damaged front air spring(s)
• Damaged rear air spring(s)

• Battery junction box (BJB) fuses 20 (30A), fuse 27 (5A), and fuse 111 (50A)
• Loose, corroded, or disconnected connectors
• Air suspension service switch is in the OFF position
• Damaged solenoid valve(s)

1. If the inspection reveals an obvious concern that can be readily repaired, correct the concern before continuing with Inspection and Verification.

1. If the concern remains after the inspection, use the scan tool connected to the data link connector (DLC) to retrieve continuous diagnostic trouble codes (DTCs) and to execute On-Demand Self-Test diagnostics for the 4WAS module.
   • If the On-Demand Self-Test is passed and no DTCs are retrieved, GO to Symptom Chart to continue diagnostics.
   • If DTCs are retrieved, go to the 4WAS Module Diagnostic Trouble Code (DTC) Index in this section.
   • If the 4WAS module cannot be accessed by the scan tool, Go To Pinpoint Test A .

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It will only process a "down command" if it thinks all the doors are closed. If you have a bad door switch, it won't lower. Any courtesy lights on with doors closed?
The dealer can conduct a diagnostic scan test and retrieve any codes that will help identify the bad circuit. Did they do that?

Do you have 4 wheel air suspension or just rear?

Assuming rear only:
The system consists of unique rear air springs, the air compressor, air lines, air spring solenoids, height sensor, air suspension control module, attachments and associated signals derived from both driver and road inputs. With these components and signals, the air suspension control module commands changes in vehicle height that are necessary for the load leveling features.
The load leveling feature rear air suspension (RAS) systems shall automatically make adjustments in vehicle height so that the vehicle is always at trim height and constant front-to-rear vehicle attitudes are maintained over the expected load range of the vehicle. Adjustments in height that are necessary to correct height differences between the vehicle's left and right sides for the RAS system shall be restricted to what can be reliably achieved with one air suspension height sensor.
The system uses one air suspension height sensor, a steering sensor, generic electronic module (GEM) and other vehicle sensors to measure driver and road inputs. The system changes vehicle height using an air compressor, two air lines and the use of air springs with air spring solenoids.

Note this section.
The air suspension system holds vehicle height when the rear hatch or any door is opened. The system stores rear vehicle height the moment any open door is detected. The system then maintains this height regardless of the addition or removal of a load. The system will return to its commanded height when all doors are closed or the vehicle speed exceeds 16 km/h (10 mph).

Air Suspension Switch
The air suspension switch supplies power to the air suspension control module. Without the air suspension control module receiving this power, the load leveling system is inoperative and will not react when the rear of the vehicle is raised or lowered. If the air suspension system is disabled by turning off the air suspension switch, a "CHECK SUSP" will appear in the RH corner of the instrument cluster with the ignition in the run position.
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The vent solenoid:

• allows air to escape from the system during venting actions.
• is part of the air compressor cylinder head.
• has a 1,103 kPa (160 psi) internal relief valve.
• shares a common electrical connector with the air compressor motor.
• is enclosed in the cylinder head casting, which forms an integral valve housing that allows the valve tip to enter the pressurized side of the system.
• has an O-ring seal that prevents air leakage past the valve tip.
• opens when the air suspension control module determines lowering is required.
• provides an escape route for pressurized air that opens when system pressures exceed safe operating levels.
• is replaced with the air compressor as a unit.

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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).
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.
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May be a bad module too.

can you hear the pump come on when the vehicle starts? Check the rear height sensor at the rear axle it might have come off

There are level control sensors they look like little arms (with joints like your elbows) mountesd on lower control arms. They may be at fault they control the height and turn the pump off when the height is reached. try adjust height first before you replace, they can be adjusted. Good Luck