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[bigbadee]

hi all hope to pick up my new car this weekend thing is think it is positive earth . its a 1960 rover p4 .The thing is that as the car is positive earth ? and doesn't have a 12v accessory point cant plug in the sat nav ,don't want to go back to the old map book so could I just run two wires from the battery to spare cig lighter that I have lying around and plug the sat nav into this .I know that this is a bodge but its just to get me home and can be sorted better when I have the time thoughts please.

[I_want_an_Omega]

You can, but it's important that you:

a) get the polarity right
b) fit a fuse in the circuit

The fuse should be quite a low value, say 3 or 5 amps, and as close to the battery as possible to provide protection to the cable in the event of any short circuit that may occur.

HTH - Rob

[Andy B]

Oh no!! ..... What will Mark say?           

[TheBoy]

Oh no!! ..... What will Mark say?           

He'll blow a fuse

[Andy B]

Oh no!! ..... What will Mark say?           

He'll blow a fuse

No guesses as to which one you'd want to blow! 

[Lizzie_Zoom]

hi all hope to pick up my new car this weekend thing is think it is positive earth . its a 1960 rover p4 .

Yes, I remember positive earths; whatever happened to them and why?

Takes me back though and reminds me of the need then (in the early 70s) to check the earth of any car.

[Keith ABS]

  One line of thought was that changing to earth polarity to negative speeded up the rusting process on the old cars
Keith B

[Kevin Wood]

Oh no!! ..... What will Mark say?           

Depends which one..

The DTM one will have kittens.

The Tunnie one will probably share his experiences. Then again, the Sennie "modification" wasn't so bad. rust isn't that great a conductor, after all. 

[Kevin Wood]

Just to say, for a temporary solution I would take a jump start pack along and power the sat nav from that.

For a permanent solution, no reason why you can't install a normal (properly installed and fused) cigarette lighter, just make sure that no metalwork on the car can contact the outside of the lighter socket or any devices you are in the process of inserting.

[MR MISTER]

Just to say, for a temporary solution I would take a jump start pack along and power the sat nav from that.

For a permanent solution, no reason why you can't install a normal (properly installed and fused) cigarette lighter, just make sure that no metalwork on the car can contact the outside of the lighter socket or any devices you are in the process of inserting.

Pardon?

[Kevin Wood]

Just to say, for a temporary solution I would take a jump start pack along and power the sat nav from that.

For a permanent solution, no reason why you can't install a normal (properly installed and fused) cigarette lighter, just make sure that no metalwork on the car can contact the outside of the lighter socket or any devices you are in the process of inserting.

Pardon?

Can you get those for in-car use now? No wonder driving standards are slipping.

[zirk]

Ah, Positive Earth, I remember them, PNP Transistors, 240 V live TV Chassis, when the world thought that electricity flows from Negative to Positive, which it does in theory.

Its all that Alexander Graham Bell's fault, the early Telephone Exchanges used Positive Earth (and still do World Wide) to reduce Corrosion on Equipment and Lines and reduce the risk of Lighting Strikes.

Actually Thomas Edison was on course for inventing the Telephone, but that Bell bloke nicked His Carbon Mic idea and beat Him to it.