So the rear air suspension on my 2001 Navigator if fully deflated. I have tested the suspension/compressor relay and it is good. If I take a jumper wire and jump the two large wires on the relay plug the compressor kicks on. This leads me to believe that the rear ride height sensor is the culprit. If I completely extend or shorten the rod on the RHS nothing changes.

1. Is there any way to test the RHS with an ohmmeter or something of the sort?
2. What step by step process should I take to ensure that I have ruled everything else?
3. Where is the best/cheapest place to purchase the RHS if I am in need of one (looks to be a dealer only part)?

Any help is really appreciated!

 

Before you buy parts you need to air up your suspension and check all of the connections of the airlines. A fairly common cause is the airline union on the driver side over the steering shaft. They crack and leak for some time and then they break entirely. Another point to check is the vent valve in the rearmost line between both airsprings. It looks like a common "T" type of fitting with only 2 of the 3 branches being used, mine leaked and caused the same symptoms as yours. There is also a "Y" type fitting near the L.R. air spring that is where the air enters to supply both rear airsprings. A soapy water mix will help in the search, just go slow and check every connection.
I doubt that the ride height sensor is the problem.

 

How do I air up the suspension... when I jumper-wire the relay connection it causes the compressor to come one, but it doesn't air up the lines? I will check all of the fittings that you mentioned, thanks for ideas.
If it's not the RHS why does adjusting the length of the sensor rod have no effect on the compressor? That's what I can't figure out???

 

I have been blessed(?) with having to aquire a number of spares over the years so I had most of the parts needed to do the following.
Parts needed:
2@ 1/8" compression type Tee fittings with nylon ferrels and brass inserts to support the plastic tubing. A Shrader valve was in the center of each Tee.
1@ electrical connector to plug into the solenoid valve at the air spring with enough wire lead to reach a 12v source of power to open the valve.

I cut the supply air line at a point near each air spring where I could access it without too much trouble and installed the Tee fitting, one on each side.

When I needed to air up the suspension I would get under the car and unplug the factory electrical connector and install the made up one. I would then get power from a 12v source and open the solenoid. Then with air from my at home or at work compressor I would air the suspension up while leaving the "Air Ride" switch off. If you turn the air ride switch back on you may lose the air you just installed. What I have described was overriding the system as the solenoids will not release the air or open until it gets an electronic signal. After airing each side up you remove the made up electrical connector asnd reinstall the original to keep it clean. Also you should use a valve stem cap on the shrader valves to keep dirt out of the system.

You can get the Tees at a hydraulic supply shop or a truck parts supply house, The electrical connector needed is from nearly any Ford, Lincoln or Mercury from the mid '90s and newer and available from most U-Pick type salvage yards.
This is not a true fix! It will make your truck useable again for a while and allow you to check all of your air connections. In order to check the connections for leaks under pressure you will have to turn the air ride back on. I suggest that you have jack stands under the frame and the wheels on the ground when checking as well as having a helper to turn it on while you are under the truck as well as to be able to listen at the front for a sudden rush of air leaking. The stands are there to prevent it from pinning you under the truck if it should leak pretty fast.
Good luck with it and keep us posted on your progress.