I have a 1990 Big Bronco and the main dome light works fine, but not the ights on each side of the main dome light. Does anyone know or have a wiring diagram for the dome lights?

 

I have a 90 also with the same problem and haven't been able to figure it out either...If I find it first I will fill you in...

 

 

If you find out please let me know as well, my 1990 F150 has a similar issue that the dome doesnt work but the two spots on the sides of the center dome does. The bulb is good but door switches and the headlight switch have no control.

 

The map lights have their own switches in the dome light assembly. That is the ONLY control there is for them. If the dome light works, then the negative (ground) for the map lights is fine. the power feed for the map lights is the LT. GREEN/YELLOW wire from fuse #8 in the dashboard fuse block feeds the map lights. Fuse #8 feeds ALL of the interior lighting circuits so if you have dome lights then its NOT a blown fuse.

 

Here's the schematic for a 88 Bronco. Appears the wiring should be the same for a 90.

2nd diagram left side Figure 2 shows where a 3 wire Gray colored connector is.
You can test for 12 volts at that connector.

Black/Pink 12 volts for Dome and Cargo bulbs when headlight dome light switch
is turned on.
Light Green/Yellow 12 volts for the two map bulbs. Hot all the time.
Black/Light Blue 12 volts for Dome lamp when either LH, RH door is open.

The wires run along the driverside rocker panel then up the B pillar.
You might find a break in the Light Green/Yellow wire where it turns up at the B pillar.

 

Don't forget to check to make sure that A) there's a bulb in the socket, never know what the previous owner did. and B) that its a good bulb. That's where I'd start before checking wires and such.