Positive or negative earth; LEDs, USBs and airbeds.

[Bob Falfa]

I've just discovered that my car is positive earth. Never having owned a positive earth car before, I find myself wondering if I should change it to negative earth? The main reason for doing so would be so I can to switch to LED lights, have a USB charger for my phone and sat nav, and a cigarette lighter that will provide electricity for my (negatively earthed) tyre / airbed pump.

So do I go to all the trouble of converting a perfectly reliable and beautiful car to -ve earth, or figure a way to plug in all my accessories?

Thoughts, discussions, answers on a postcard would be appreciated

 

[Bill Eisinger]

LED's only allow current flow in one direction so you would need to wire them with the connections swapped...I believe you would do the same with the cigarette lighter to accommodate a phone charger. Converting to negative ground may be just as easy and will make things more simple going forward...depending on how stock your car is you basically just need to swap the battery cables, ammeter connections, tach connections (if tach is electric), and clock (if you have one)...if your car still has a generator then you have to repolarize it but that's not difficult either. This link has been posted before but its a simple explanation on what to do for a conversion. https://www.askthemechanic.co.uk/classic-cars/sunbeam-alpine/negative-earth

 

[hartmandm]

Joe Parlanti does sell positive earth LED bulbs - http://velocesolutionsllc.com/, but I see you are in the UK. You can probably find them in the UK, too.

Stock cigar lighter wire is a bit thin and no separate fuse. You might need at least 15 amps capacity for the pumps? I'd probably just add another cigar lighter connector on its own fused circuit (or you could re-wire the existing dash lighter), with beefier gauge wires, always hot, and wired up the same as a negative earth car. Allows you to use standard lighter powered stuff with minimal effort.

Mike

 

[beamdream]

Truly not a big deal to swap over to negative earth, makes it much easier to operate modern accessories. Plenty of online articles on how to do.

Then as others have said, swap necessary wires, tach, amp, battery earth and you're done.

 

[loose_electron]

The USB plug and LEDs in the running lights can all be set up for either negative or positive earth.
There are LED bulbs of both + and - polarity. Also, modern light sockets are plastic, and have 2 wires, so those can be substituted as well if you want.

My personal preference would be swap to negative earth so that you can go to a single wire alternator and get rid of the unreliable generator and regulator setups that were in the original car.