If the vehicle is indeed late production, the entire electrical circuit is changed because one relay is solid state and the other is mechanical. Here's an excerpt from the TSB on that.
F: COMPRESSOR RELAY CHANGE - VEHICLES BUILT AFTER FEBRUARY 3, 2003
Navigator vehicles built prior to February 3, 2003 use a solid-state relay for the air suspension compressor motor. The control line from the module is grounded to energize the relay. The relay is located on the radiator support on the right side just behind the headlamp assembly.
Both Navigator and Expedition vehicles equipped with air suspension built since February 3, 2003 utilize a mechanical relay for the compressor motor. The control line from the module is grounded to energize the relay. The relay is located on the compressor bracket just above the compressor attachment to the radiator support on the right side.
In addition, there are important wiring differences between the two relays. Early production vehicle relays have one power feed, where late production relays have two (both are hot at all times). The solid-state relay also employs an external full-time ground, where the mechanical relay does not. See Figure 2 for more details.
Friday, January 11th, 2013 AT 3:35 PM
