There are four two-watt light bulbs in the center panel of the DeLorean interior. These are to illuminate the HVAC controls. There is a similar bulb, on the same circuit, in the shift quadrant plate on automatic transmission equipped cars (the shift indicator bulb does not dim).
The lights come on brightly with the ignition and are dimmed by a resistor when the headlights are turned on. In this normal mode, the heat from these incandescent bulbs will often fade the AC panel decal and is thought to contribute to early failure of the radio. One way to alleviate this is to make a simple modification that will cause the four lights to come on with the headlights only, and then at the reduced intensity.
Locate the panel illumination relay (#29 in the Service Manual page M:07:02). The center pin of this relay socket has a light green/white wire that connects to the resistor. Either clip off the wire or pull the terminal out of the socket. This will disable the direct feed from the auxiliary relay that bypasses the resistor. The AC panel lights will now only light up at the lower intensity when the headlights are turned on, and will be dark at all other times.
Revised 6/30/2016 DAS [revised wiring mod]