Air suspension

As much as I hate to say it, it have to be ajusted at the dealership the tool to do the job is about 6000.00 so its best to have dealer do the job

See pic it may be easier to see from bottom

Was told by a car dealer that the air suspension in navigators have a tendency to go out around the 125,000 mark, would this be true or just a salesman being a salesman?

It could be a bit of both. Yes, he sells stuff, that's his job. The term "go out" seems vaguely scary. Worn is possible.

The rubber air bags probably would dry rot and start leaking about that time which would be understandable and repairable with new bags. They are rubber and rubber doesn't last forever.

Frank there is a technical bulliten about your suspension, read this:
AIR SUSPENSION PERFORMANCE - HEIGHT SENSOR LINKAGE ARM DISENGAGING TECHNICAL SERVICE BULLETIN Reference Number(s): 06-15-10, Â Date of Issue: Â August 7, 2006 Related Ref Number(s): 06-15-10 ARTICLE BEGINNING ISSUE Some 2003-2006 Expedition and Navigator vehicles equipped with an air suspension may exhibit an air suspension height sensor linkage arm disengaging from the suspension ball stud or height sensor rotating arm. This concern typically occurs with the rear sensor ( Fig. 1 ) but may occur with the front sensors as well. If this occurs, the symptom will typically be the vehicle leaning to one side, the vehicle sitting too low/high, a harsh ride, and/or an inoperative air suspension. In addition, this concern may result in diagnostic trouble code (DTC) C1725 (air suspension front pneumatic failure) or C1726 (air suspension rear pneumatic failure). ACTION When a linkage arm becomes disengaged, do not re-attach the arm and do not replace the sensor unless broken. Instead, install a revised linkage arm on all three (3) sensor assemblies, even if they have not detached from the ball stud. Refer to the following Service Procedure. Fig. 1: Disengaged Linkage Arm SERVICE PROCEDURE Fig. 2: Old Style Link Fig. 3: New Style Link 1. Replace linkage arms on all three (3) sensor assemblies following Workshop Manual (WSM), Section 204-05. FORD: 2003-2006 Expedition LINCOLN: 2003-2006 Navigator NOTE: LINKAGE ARMS USED AS ORIGINAL EQUIPMENT ARE SHOWN IN Fig. 2 . REVISED LINKAGE ARMS (Fig. 3 ) HAVE A NEW DESIGN THAT MAKES IT MORE DIFFICULT TO DISENGAGE FROM THE BALL STUDS. NOTE: IF THE SENSOR ASSEMBLY NEEDS TO BE REPLACED FOR ANY DAMAGE/FAILURE OTHER THAN THE ONE DESCRIBED IN THIS TSB, THE REPLACEMENT ASSEMBLY IS SUPPLIED WITH A NEW STYLE LINKAGE ARM, SO THERE IS NO NEED TO ORDER ADDITIONAL LINKAGES FOR THE SERVICE REPAIR.2. Discard the old linkage arms. PARTS INFORMATION

Disconnect it as shown here.

Start by reading the guide below on wiring testing and relay testing, they will help you figure out what is stopping the compressor from turning on

https://www.2carpros.com/articles/how-to-check-wiring

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Attached below are the wiring diagrams for the air suspension system