Where is the GEM located on a 1999 lincoln navigator

Behind the center of the instrument panel . Take out radio an HVAC panel

heres your manual
1999 Lincoln Navigator Manuals

This model doesn't use a GEM module.

All this comes from the GEM module,You will need to repair the driver door lamp switch located in the door lock assemble.

I have a 1999 vehicle and the connection is under the dash by the Drivers right leg.

go to the ford lincoln mercury website and enter you year, make, model of your vehicle. It will let you download a pdf version to your computer. then open the document and go to page 135. this is free don't pay for something you shouldn't, you already got the vehicle. this is just information. Fuse Location,Fuse Amp,Description
1) 25A Audio
2) 5A Clock, Overhead Trip Computer, Electronic
Automatic Temperature Control (EATC),
Powertrain Control Module (PCM), Cluster
3) 20A Cigar Lighter, OBD-II Scan Tool Connector
4) 15A Autolamp Module, Remote Entry Module,
Mirrors, Memory Module, Adjustable
Pedals, Air Suspension Switch
5) 15A AC Clutch Relay, Speed Control Module,
Reverse Lamp, EVO Module, Climate Mode
6 5A Cluster, Overhead Trip Computer, Compass,
Steering Sensor, Brake Shift Interlock
Solenoid, Air Suspension Module, GEM
Module
7 5A Aux A/C Blower Relay, Console Blower
8 5A Radio, Remote Entry Module, Cell Phone,
Clock, GEM Module
9 — Not Used
10 — Not Used
11 30A Front Washer Pump Relay, Wiper Run/Park
Relay, Wiper Hi/LO Relay, Windshield Wiper
Motor, Rear Washer Pump Relay
12 — Not Used
13 20A Stop Lamp Switch (Lamps), Turn/Hazard
Flasher, Speed Control Module
14 15A Rear Wipers, Running Board Lamps,
Battery Saver Relay, Interior Lamp Relay,
Accessory Delay Relay (Power Windows,
Flip Windows, Audio)
15 5A Stop Lamp Switch, (Speed Control, Brake
Shift Interlock, ABS, PCM Module Inputs),
GEM Module
16 20A Headlamps (Hi Beams), Cluster (Hi Beam
Indicator)
17 10A Heated Mirrors/Rear Window Defroster
Indicator
18 5A Instrument Illumination (Dimmer Switch
Power), Clock (Dimmer)
19 — Not Used
20 5A Audio, Four Wheel Air Suspension (4WAS)
Module, Memory Module, GEM Module,
Digital Transmission Range Selector
21 15A Starter Relay, Fuse 20
22 10A Air Bag Module
23 10A Electrochromic Mirror, Aux A/C, Heated
Seats, Trailer Tow Battery Charge,
Turn/Hazard Flasher, Console Blower Door
Actuator
24 10A Climate Mode Switch (Blower Relay),
EATC (via fuse 7), EATC Blower Relay
25 5A 4 Wheel Anti-Lock Brake System (4WABS)
Module
26 10A Right Side Low Beam Headlamp
27 5A Foglamp Relay and Foglamp Indicator
28 10A Left Side Low Beam Headlamp
29 5A Autolamp Module, Transmission Overdrive
Control Switch
30 30A Passive Anti Theft Transceiver, Cluster,
Ignition Coils, Powertrain Control Module
Relay
31 10A Rear Integrated Control Panel (Audio), CD
Player, Cell Phone
Relay 1 — Interior Lamp Relay
Relay 2 — Battery Saver Relay
Relay 3 — Rear Window Defroster Relay
Relay 4 — One Touch Down Window Relay
Relay 5 — ACC Delay Relay

hope this helps.

Under the coil covers,on the valve covers.
One to Four ,on pass side,front to back
Five to Eight,on driver side,front to back

its located in the r/f of the engine compartment near the washer fluid reservoir.

There is a Technical Service Bulletin which indicates that moisture on or in certain wiring harnesses and electrical components will cause the GEM (Generic Electronic Module) to FAIL. Look up: Gem problem on Navigators.

your problem is in you gem moduel and only a dealer can check that.