The 20a fuse in the interior fuse panel for the 1b spot= SIG/B/U LPS/BTSI/LCM keeps blowing when I put the car into gear. Not sure whether it is because of a shortage or what?

Turn Lamps
With the ignition switch in the RUN position, battery positive voltage (B+) is supplied from the IP fuse block T/SIG/BU LP/BTSI fuse 1B via CKT 539 (PNK) through the turn signal flasher to the normally closed switch in the turn/hazard switch via CKT 16 (PPL). With the turn switch in the left turn position, battery positive voltage (B+) is applied through the turn switch and two paths to the turn lamps. One path is to the left front park/turn lamps and the side marker lamps via CKT 14 (LT BLU). The second path is supplied to the left tail/stop/turn lamps via CKT 18 (YEL). The lamps go on immediately. The lights begin to flash when the current heats up the timing element in the flasher, and the flasher repeatedly opens and closes the circuit. A similar procedure is followed when the turn switch is in the right turn position. Battery positive voltage (B+) is supplied to the right front park/turn lamps and the side marker lamps via CKT 15 (DK BLU). Battery positive voltage (B+) is supplied to the right tail/stop/turn lamps via CKT 19 (DK GRN).
Hazard Lamps
Battery positive voltage (B+) is supplied at all times from the IP fuse block BRK/HZRD LPS fuse 6B via 140 (ORN). The current flows through the hazard flasher to the normally open switch in the turn/hazard switch. With the hazard switch in the ON position, battery positive voltage (B+) is applied through the turn/hazard switch to all four paths used by the left and right turn lamps. The following components flash on and off:
• All turn lamps
• Both indicators
With the hazard switch in the ON position, the turn circuit is always open, and the hazard flasher controls the lamps.

Check the courtesy lamps relay . The fuse that blows ,just to make sure we have the right one , INT LPS fuse 10amp ,located in the underhood fuse box.
The relay is located in the rear compartment relay center 2

Does your Grand Marquis have head lamps with auto lamps ? Which fuse keeps blowing ? Could be a shorted LCM - lighting control module ?

Lighting Control Module (LCM)
The LCM eliminates the electronic interference and heat associated with the thermoelectric devices used previously. The LCM is a microprocessor-based module that controls several vehicle subsystems. It responds to electrical input signals from various switches, sensors, and external modules..

Visual Inspection Chart Mechanical Electrical

• Headlamp switch

• Central junction box (CJB) fuse(s).
  • 1 (15A)
  • 9 (20A)
  • 26 (10A)
  • 15 (7.5A)
  • 7 (10A)
• Headlamp bulb
• Circuitry
• Headlamp switch
• Lighting control module (LCM)
• Underhood power distribution box (PDB)
  • F104 (40A)
  • F01 (20A)
  • F02 (25A)

Disconnect the cigar lighter and see if the short goes away, I will bet it does.

my 1998 jeep grand cherokee electrical system started shutting down while driving. i heard ticking sounds coming out from by the interor fuse box. after checking each fuse the fuse in the #16 slot (the fuse for the CTSY LPS 10A) is causing the ticking sound while putting the fuse in and out.whats next? please help.

your car has a dead short/bring to garage to find short/do not upgrade fuse it will burn wires

Soldering the new bulbs in may have done something to the LH DIMMER MODULE ! The 10amp INT LPS fuse located in the I/P fuse box is good ? Is the dimmer switch at full bright ?
When the park lamps are on, battery positive voltage (B+) is supplied through the instrument panel (IP) fuse block INT LPS fuse via CKT 32 (YEL) to the dimming switch. The dimming switch supplies a variably controlled voltage to the dimmer module(s). The potentiometer in the panel dimming control cannot provide enough current in order to operate the panel lamps. The dimmer module(s) amplifies the current, supplying the variable voltage to the panel lights. As the amount of the current increases, the lamps become brighter. As the amount of the current decreases, the lamps become dimmer.
Buick
There is only 1 dimmer module that supplies current to the panel lights. The left dimmer module supplies current via CKT 8 (GRY) to the following components:
• The headlamp switch
• The door switch flood lamps
• The heater and A/C control
• The door handle flood lamps
• The passenger temperature control
• The ashtray lamp
• The shift select switch lamp
• The instrument cluster
• The steering wheel controls
• The reset switch
• The trip odometer
• The radio
Parade Dimming
The parade dimming feature prevents the dimming of the VF displays when daylight is sensed by the lamp control module (LCM) and the park lamps are turned on manually. If the LCM senses night time conditions and the park lamps are on, the LCM allows the VF displays to be dimmed.
All of the modules with the VF displays receive the dimming level from an input on CKT 8 (GRY) or CKT 1244 (BRN). When the LCM determines that the above conditions are met, the LCM sends a signal to the instrument cluster and the radio via CKT 390 (YEL). For Buick, the radio then relays this information to the heater and A/C programmer and passenger temperature control via CKT 724 (PPL/WHT). The modules with the VF displays then adjust the dimming level of their VF displays to match the level of the incandescent lights.
LH Dimmer Module
Under the left side of the IP, on the left side of the steering column brace

The 1999 Fuse Box Diagram is as follows:

Column 1 (Top to Bottom)
Driver Window Relay
Interior Lamp Relay
Driver Unlock Relay
Battery Saver Relay
Hazard Lamps (15A)
Diagnos (10A)
Cigar (20A)
Front Wipers (30A)
Air Bag (5A)
ABS (10A)
Shift Interlock (5A)
Blank

Column 2 (Top to Bottom)
High Beams (15A)
Deck Lid Release (15A)
Mirrors/Antenna (5A)
Head Lamp Illumenation (5A)
Light Out Module (5A)
EEC Ignition Coil (20A)
Brake Lamps/ A/C (15A)
Instrument Illumenation (5A)

Column 3 (Top to Bottom)
Accessorty Delay Relay
Rear Defrost Relay
Tail Lamps (5A)
Battery Saver (10A)
Wiper and Vaps (5A)
Rear Wiper (15A)
Turn Signal (10A)
Air bag/ Alt LPS (A)
Starter Relay (10A)
Left Low Beams (10A)

Column 4 (Top to Bottom)
Switch Illumenation (5A)
Def Sw Illumenation (10A)
Stop Lamps (15A)
Radio (5A)
Radio Memory (5A)
Right Hand Power Locks (20A)
Gauges/ Warning Lamps (5A)
Radio Mute (5A)
Right Low Beam (10A)

Hope this helps.

Your fuse panel is located by the emergency brake.Depress the two tabs and the fuse box will swing down, the panel diagram is written on the panel door.