How To Add Accessory Power Outlets To Your Classic

When our classics were new, many of them boasted just two accessories, items often added by the dealer: an ashtray and a cigarette lighter. Times have changed, and ashtrays are seen less and less often. 

Cigarette lighters, however, have kept up with the times. Just as celebrities and politicians reinvent themselves, so have these contraptions. Now they’re called accessory outlets, and they’ve become ubiquitous. Even though they rarely house a lighter element, these power ports are practically standard equipment in today’s new cars.

Why the need? Look at all of the stuff we take with us on the road. We use these outlets to charge and power our cell phones, iPods, navigation systems, air compressors, camera batteries, USB devices, CB radios and so much more. 

Fortunately, just as the dealers easily installed these outlets in the past, so can we. Before taking our Modern Midget project car on the road, we performed a quick tweak to induct the car into the age of pocket-sized electronics. 

Step 1

We wanted to take our modern conveniences on the road when traveling in our MG Midget, so we first needed to do some wiring. We found this three-outlet “extension cord” at the local auto parts store for about $15. It’s intended to be plugged into an existing lighter socket/accessory outlet. Our plan was to permanently wire it into the car instead of simply plugging it in.

Step 2

After doing a trial placement and taking some quick measurements, we cut off the power plug and excess wire. Since we’re installing the outlet into a car with Lucas electrics, we used some Lucas terminals and a specialized crimping tool to terminate the wire—both available from British Wiring. If this were a different make of car, we’d have used the appropriate wire and terminals to provide a clean, factory-style installation.

Step 3

We drilled two small holes and mounted the outlets with two sheet metal screws. We put it below the dash in the passenger footwell, where it was fairly concealed but still easy to reach.

Step 4

When adding an accessory like this, too often people just run a set of wires directly to the battery or to the first live circuit they find. That’s not a good strategy. 

First, we looked at the load requirements of the accessories we’re planning to run—less than 5 amps. Then, we determined the load that the wiring and outlets could handle to be sure we wouldn’t exceed it with our accessories; the wiring could handle 25 amps, so no problems there. 

Then we decided whether we wanted the power to remain on or to be switched on and off with the key—we picked always on. Finally, we found a circuit that was appropriate and could handle the load. In our case, as is the norm for most Lucas-equipped cars, this was the purple circuit. This circuit is always on and fused at 35 amps. In our car, this circuit runs the horns and the dome light, which together use no more than about 25 amps, leaving us enough capacity for our accessories. We plugged our accessory socket into the nearest set of Lucas connectors. 

We chose not to use an additional fuse, as we felt our loads on this circuit wouldn’t cause any additional risk. The purple wire is the 12V+, while the black wire is the ground (12V-).

Step 5

After about 15 minutes of work, we had a functional place to plug in our toys that didn’t look too conspicuous. Now we can travel in style. 

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View comments on the CMS forums
californiamilleghia SuperDork
10/14/20 10:05 a.m.

some of them have USB plugs too , thats what I have......

wspohn Dork
10/14/20 11:50 a.m.

Yup - that's what I did on the Jamaican-MGA so I'd be able to run a GPS and radar detector. On a trip it looks like a bundle of snakes under there.

10/15/20 12:48 p.m.

In reply to wspohn : Don’t forget some cars are positive ground  


300zxfreak Reader
10/15/20 4:44 p.m.

What the hell is a CB radio ??


Breaker, breaker............anybody there ?

RadBarchetta New Reader
10/30/21 8:40 a.m.

This article is from 2011... as an update, you might consider skipping the "cigarette lighter" and just wire in a couple USB ports. All depends on what you plan to plug in, of course, but it's now 2021. My phone does everything.

Bardan New Reader
10/30/21 12:20 p.m.

Older Brit cars have a 12 amp 20 pound generator built by the Prince of Darkness. With headlights on, wipers working, radio playing and a little wire resistance thrown in, the battery will discharge. Now add more of a load from electronic toys and soon the whole drive experience will stop.

Mike (Forum Supporter)
Mike (Forum Supporter) UltraDork
10/30/21 1:44 p.m.

Photo of usb adapter in situ.

I opted for the USB route, using a 12v water-resistant unit designed for motorcycle use. I wanted it hidden out of the way, so it's far forward in the passenger footwell, mounted with a nut on top of an existing screw. 

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