I think you might have fried your dimmer dial circuit. There is a test procedure in the service manual on page: 9-18-25
The dimmer doesn't reduce the voltage to get dimmer lighting, it instead pulses out full power with shorter and shorter intervals. I'm pretty sure a regular voltmeter would show that and I'm almost positive an old school meter with a moving needle would work to test it. The mechanical needle would absorb the bouncing pulses of voltage and give a steady reading. I don't think an oscilloscope is needed like they say in the manual.
I'm pretty sure you could 'bypass' the dial with a jumper but I'm not sure which terminals get shorted,... that way you'd have dash lights but at full brightness. (I'm having a hard time following the circuit diagram)
You may of course just have a blown fuse somewhere,... they mention the TAIL 15 A fuse.
OK,.. I stared at the circuit diagram again and I'm around 90-95% sure that if you disconnect the dimmer dial and jumper the B+ to the C terminal (light green with a black stripe wire, with the white with a blue stripe wire,... that's the two middle terminals,... one side of the plug is empty and the other is ground,... don't jump anything to ground.), it will give full brightness on all your dash lights. You would do that at the connector not at the dimmer dial. If your dash lights come on then you know it's the dimmer dial and you've got lights until you get a new dial,... perhaps at a junker for a few bucks.
I just noticed your post about the "recirculate" light dimming,... if you disconnect the dimmer dial and your "recirculate" light goes back to full brightness then it's almost for sure that the problem is your dimmer dial.
PANEL LIGHT CONTROL SWITCH REMOVAL/INSTALLATION
1. Disconnect the negative battery cable.
2. Remove the driver-side side panel.
3. Remove in the order indicated in the table.
4. Install in the reverse order of removal.
Panel Light Control Switch Removal Note
1. Insert your hand into the hole in the driver-side side panel, grasp the tabs of the panel light control switch and
pull it forward to remove.
1 Screw
2 Connector
3 Door switch
1 Panel light control switch
(See 09–18–25 Panel Light Control Switch Removal Note)
2 Connector
LIGHTING SYSTEMS
09–18–26
PANEL LIGHT CONTROL SWITCH INSPECTION
1. Remove the panel light control switch. (See 09–18–25 PANEL LIGHT CONTROL SWITCH REMOVAL/INSTALLATION.)
2. Connect the negative battery cable.
3. Connect the connector to the panel light control switch.
4. Measure the voltage at the panel light control switch as indicated below.
5. Disconnect the panel light control switch connector before inspecting for continuity at terminal D.
• If not as specified, inspect the parts listed under “Action.”
• If the parts and wiring harnesses are okay but the system still does not work properly, replace the panel light control switch.
Terminal Voltage List (Reference)
Terminal C inspection
1. Measure the wave pattern of the C terminal on the panel light control switch using an oscilloscope.
2. Set the headlight switch to either the TNS or headlight position.
3. Set the panel light control switch to the brightest position.
4. Verify that the pattern on the screen is as shown in the figure.
Terminal Signal Connected to Test condition Voltage (V)/Continuity Action
A — — — — —
B TNS TNS relay
Headlight switch at TNS or headlight position B+ • Inspect TNS relay
• Inspect combination switch
• Inspect TAIL 15 A fuse
• Inspect related harness
Other Below 1.0
C Illumination Each illumination Inspect using an oscilloscope
(See 09–18–26 Terminal C inspection) —
• Inspect each illumination
• Inspect related harness
D Ground GND Constant: inspect for continuity to ground Yes • Inspect GND
LIGHTING SYSTEMS
09–18–27
5. Verify that the pattern on the screen matches the pattern shown in the figure as the panel light control switch is gradually turned to the darkest position.