Is there any cheap way to rewire an 1988 Honda Accord so that the cigarette lighter works when the key is not in the ignition?

Answer 1

The radio and cigarette lighter are supplied by the same 15A relay-switched bus. The wire may be red/white from the fuse block and white/red after the relay, although the color code may vary over a span of model years. The relay is located behind the front console, so be prepared to perform extensive disassembly to reach it; it will be easier if both front seats are removed from the car. It is recommended that the existing wire to the cigarette lighter be left as-is, in the event that you might want to return the wiring configuration to as-built condition. Just disconnect the wire from the cigarette lighter and make sure that the end is insulated with tape or shrink tubing so that it can't inadvertently short to any grounded metal. Tap into the unswitched side of the 15A bus at the relay connector and run a new

14 AWG stranded, insulated copper wire wire to the cigarette lighter. This alternate wire to the lighter socket will still be protected by the 15A fuse that supplies power to the radio/lighter relay, so it is not necessary, or even desirable, to add another fuse in the line.

After this modification is performed, the radio should shut off when the ignition switch is off, but the cigarette lighter should be always on.

If you replace the relay with a shunt, instead of rewiring the cigarette lighter socket, both the radio and lighter socket will be on all the time. This may be convenient if one wants to listen to the radio while the ignition key is removed, but one must always be vigilant to turn the radio off before the engine is shut off and turn the radio on after the engine is started. The relay has two purposes:

1. Keep the radio off the +12V bus during startup and shutdown to protect it from "load dump" surges.
2. Disconnect the radio and cigarette lighter circuits when the engine is off to prevent the battery from being inadvertently drained.