Cig Lighter socket polarity

[doug748]

I have wired the cigerette lighter sockets on my boat in line with what I thought to be auto standard practice - centre earth (negative). Taking apart the plug of my Garmin GPSMAP 76, I discovered that the centre is wired red and the manual confirms this as the Positive feed.
What is going on here? I have been running on reverse polarity, yet the set has worked fine.

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[oldharry]

Standard auto practice has the centre pin live (+) and the case return. It is quite possible the Garmin has a 4 way diode rectifier in its power supply which allows it to work on reverse polarity.

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[doug748]

Electrical genius or what. I just went out to check in the car and fused the circuit! I must investigate this properly. The portable VHF and phone charger both work OK as well......

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[snowleopard]

lucky you. polarity was reversed on a friend's boat and blew my mobile phone charger.

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[floatything]

You think that is a problem? I ended up reversing the polarity of my entire dear old (+ve earth) Landrover so that I could run things off the ciggy lighter and have a modern radio. Oddly it was quite an easy process - flip the battery terminals; swap leads on the ammeter, and spark a wire across the dynamo to reverse the polarity of the coil windings.

Next thing is to swap the landrover.......



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[doug748]

As you were gentlemen. I now find I had wired up the thing correctly all along. Obviously suffering from pre-Christmas fatigue syndrome.

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[Piere]

I bought a garmin chartplotter a few years ago with a ciggy plug on the wire
cost at £ 800 from jos boone chandler at middleburg , holland
I needed to change this to my own choice of 12 volt power on the boat
with some trepidation I changed the plug scrapping the ciggy socket and fitting my own system.

centre wire on the ciggy unit was to positive and changed as found.

The plotter has worked without fault for 3 years .

If your plotter has worked with no problem then either the unit can work on both polarity or you have made an error , you baffle me as i was told to be very careful to make sure the polarity was right when i rewired the power lead .
RSVP if you can as i am intrigueged


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