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MG MGA - Cigarette lighter/charger

With winter coming I thought it would be an idea to fit a cigar lighter so that I can plug in my smart charger quickly and easily. Just a few simple questions on which I would appreciate some help/tips

1. Any recommendations on best place to locate it? I was thinking behind passenger seat and connecting direct to battery or maybe better up front and connect to horn fuse.
2. I am still on positive earth , and happy to keep it that way for the time, so will obviously need to be careful about isolating it from the metalwork.
3. I would also like to use it to charge up phone etc when using the car. Does this mean I need to ensure the phone doesn't touch earth either?
4. I guess I should put in a line fuse. I am thinking one fuse should be sufficient, and that one in each lead would not add any extra protection?
4.any recommendations on supplier of cigar lighter that is suitable for isolating from earth?

Graham M V

I have a coupe and a roadster and bought small sockets from an electronics store and placed each on the board behind the driver's seat. At the same time I installed in-line fuses. I also bought suitable two-pin plugs and attach the charger leads to them. I use automatic chargers and keep them "on" all of the time. I have not bought new batteries since I did all of this some years ago.
Barry Bahnisch


I mounted a 2-pin Whale socket on to the non-conductive wooden backboard and connected the terminals directly to the battery. I attached the plug to the charger, taking care to attach the wires to suite the polarity.

You could run a second set of wires from the socket to a cigarette lighter also mounted on the wooden panel. Alternatively just use the cigarette lighter socket to suit all needs. If it's on the wooden board you don't have the earthing issue through the frame and you can wire it up conventionally as if negative earth (Cigarette lighter body to negative battery terminal and central positive terminal to the battery positive terminal. The only problem may be mounting the socket on the thick board. Will there be enough thread on the socket body to screw on its securing nut? My Whale socket attached fine as it has attachment holes and you just need 2 suitable bolts to suit.

Steve Gyles

Is there a compelling reason for you to stay with Positive ground? If not, converting to Negitive ground is easy and eliminates all chances of having issues with accidently grounding something that is plugged into your power socket. I mounted mine on the bottom of the heater shelf forward of the heater controls and powered it from the starter switch through a fuse. It is easily reached but is not visable unless you lean down and look under the dash.
Ed Bell

I did the same as Barry and Steve fitting a small period two pin socket behind the passenger seat. The cables run under the carpet and directly to the battery terminals with an in line fuse on the live. I have one plug on my battery conditioner connector and another on a charger (lighter) socket on a longer wire. This can run along the and onto the top of the transmission tunnel. I thought about making a removable bracket of some kind, but have not done so yet.

N McGurk

Im with Steve on this, fit the socket on the plywood bulkhead to the rear of the seats.

Position it between the seats so that you can get to it with the seat back raised. There isnt a lot of space there but it is really handy to be able to plug into it there whilst you are driving.

You can wire it directly to the battery with an in-line fuse and it can be in either polarity as the socket is fitted through the plywood with no chance of any accidental short circuit. I used a Maplins marine cigar lighter type socket, this is of all plastic construction and has a built-in water proof cover that is great for my roadster.

DONT fit it through the bulkhead immediately behind the centre of the passenger seat like I did.

What I didnt take into account was that the plug when inserted into the socket, protrudes 2 to 3 inches out into the cockpit.
So when I plugged it into the socket and put the seat back into the upright position, it just smashed the plug through the back of the socket and wrecked it!

I use the socket to plug my battery conditioner into when the battery isolator is switched off, a 3 amp fuse is fine for this.
When I am driving I plug a small multi socket into it which has two cigar lighter socket and also a USB port that I can use for my iphone or camera charger.


Colyn Firth

Colin, I thought about putting mine between the seats, but the side curtains rest there. If you stay near the tunnel there is plenty of room even with the seat fully back. A plug and cable to the top of the tunnel under the dash with a lighter socket gives access to the power supply while driving.

If you use a CTEK battery conditioner then you can kill two birds with one stone:
It plugs into the connector that is left attached to the batteries to provide a power source when driving!
N McGurk

Neil, I should have mentioned that I squeezed the socket down in-between the passenger seat and the transmission tunnel, well below the the top of the tunnel and so the sidescreen bag doesnt interfere with any plug you use.
Colyn Firth

Thanks thats really helpful. As I mentioned, I am still positve earth, and if I change, it means scrapping my petronix, as mine only works on + earth.
My only question now, if someone knows, having wired my socket and cigarette lighter "in reverse" which is not a problem, do I need to make sure my phone doesn't touch earth?
Graham M V

Photos of layout of isolation switch and 12v outlet on my negative earth MGA - passenger side (components are Narava ) - outlet is isolated when the isolator switch is turned off! Isolator switch is on the earth side.

Mike Ellsmore


I have a similar set up to that of Steve Gyles, on the wooden backboard, for keeping my (positive-earth twin 12-Volt) batteries fully charged. The socket is connected direct to the batteries via a single in-line fuse.

While you are doing wiring tasks, you might consider adding a cigar socket up front. My MGA is mainly used for Continental trips, so I have fitted a cigar lighter socket under the dash on the passenger's side to allow a GPS navigator (or other accessory) to be connected. The socket is plastic and mounted, using existing holes, on the top of the steady bracket for the dash. It is out of sight, but easy to reach.

M D Card

Thanks. Yes I am happy about fitting this up. Nice easy job to do in the garage on a wet day. I am just a bit uncertain whether the mobile phone holds negative charge on its own "chassis". But it will be easy enough to check when I buy a new charger, which I need to do anyway, having just changed phones.
Graham M V

Question for Neil M unrelated to the socket. Where did you get the seal rubber for the edge of the floorboard which the battery cover sits on. It looks a good soft sealing strip in your photos.

John Francis

I just got a cigarette lighter socket in Halfords, which has a plastic mounting, so no worries with my +ve earth. I then made a sheet aluminium bracket and screwed it to the top of the for & aft dashboard support strip on the passenger side, such that the socket is positioned horizontally facing the driver's side. A short wire with a five amp in-line fuse goes neatly through to the nearby fuses so that it is live with igntion off. I use it for charging, sat nav and phone.
P N Tipping

John, it's from Todd Clarke.
N McGurk

Thats exactly what I am now planning. Connected to the "horn fuse". Its ok for your phone to touch the bodywork of car I assume?
Graham M V

I checked which one was live all the time and connected up to that, same as the Kenlowe and the bilge blower.
My phone's plastic, hadn't even thought of that...
P N Tipping

This thread was discussed between 06/10/2012 and 13/10/2012

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