DIY: Rewiring the cigar lighter to only run in accessory mode

[edbods]

Unfortunately for me, the cigar lighter wire is crimped directly to the fuse holder terminal in the fuse box. Fortunately, it was easy enough to add a relay in, and have it activate when the key is turned to accessory mode.

Stock cigar lighter socket, with a pink and red wire going into it. A 0.156/4mm male bullet terminal fits perfectly.

Red goes to the relay. Had a toyota one lying around:

The cigar lighter terminal pointed out below, as well as the relay trigger/signal circuit. The piggyback will be for the head unit that I'm going to install under the dash, it has its own fuse which was the reason for using the piggyback.

Signal circuit ground point:

Factory wiring diagram:

Modified:

I like that I didn't have to cut the factory harness or anything like that. If the next owner after me wanted to return everything to stock it's just a matter of pulling the wires out.

 

[UGW]

This is a nice setup! I also try to design all my changes so that they can be easily returned to stock; it's more complicated this way, but it's also a fun challenge.

I did something similar when I added a few gauges. I wanted the gauges to illuminate at the same time as the stock instruments, but the new gauges are LED and not dimmable. I couldn't directly connect them to stock circuit - they would only work when the dash was on "full brightness". I fixed it by adding a relay triggered off the "instrument lighting" fuse on my fuse block. (In 1963, the fuse is downstream of the switch, so it only sees current when the lights are on. Weird, but convenient?) With this setup, even the lowest amount of current on the lighting circuit makes my gauges light up by triggering the relay. As an added bonus, I wired the "power" for the relay to a different circuit, so I wouldn't put any more load on that tiny, 2A fuse used by stock the instruments.


I'm also a HUGE fan of these "FlexFuse" for reversible wiring - no tools needed, and they can be undone in minutes. They let you use modern fuses, and you can tap from the front of the block instead of the back.
https://www.cjponyparts.com/flexfuse-fuse-converter-standard-glass-with-auxiliary-connector/p/FFC2/

 

[edbods]

Nice, I've been keeping an eye on those flexfuse adapters for a while now, I do want to get that but wow the price of them...