Three questions:

1. Do all cars nowadays have the same earth or do they still vary?

2. Why would a manufacturer choose one over the other?

3. Do modern cars still use the bodywork as the earth return? Seems to me that CANBus might want a slightly more reliable return than 1/2 ton of steel.

Thanks in advance.

SR

1. I was talking to someone about positive earths the other day. Only early cars used positive earths and the change over to negative earth happened between 1966-1972.

I've not heard of any cars nowadays with positive earth.

2. There are no advantages or disadvantages between negative and positive earth, they were changed to negative earth to use alternators instead of dynamos because they were better

Three questions:

1. Do all cars nowadays have the same earth or do they still vary?

YES, ALL MODERN CARS NOW USE NEGATIVE EARTH. IT CAME IN WITH THE INTRODUCTION OF ALTERNATORS.

2. Why would a manufacturer choose one over the other?

THEY DON'T NOW.

3. Do modern cars still use the bodywork as the earth return? Seems to me that CANBus might want a slightly more reliable return than 1/2 ton of steel.

BODY WORK IS USED AS IT IS EASIER TO GET TO AND DOESN'T REQUIRE THE EXTRA WEIGHT OF THE "EARTH" WIRE.

Thanks in advance.

SR

AND TO BE ACCURATE IT SHOULD BE THE GROUND RETURN, NOT EARTH, BUT EVERYONE CALLS IT EARTH RETURN.

Back in the '60's, when I swapped the earth on my Mk1 Hillman Imp from positive to negative, there was talk of negatively grounded vehicles being less prone to corrosion. IIRC the cathode was considered less prone to corrosion than the anode :wonder:

Whatever........the swap made no difference to mine. It still continued to rot the sills out every couple of years.

Robjon is part-right; the issue was with the return strap connector rotting out of the shell on positive return cars rather than offering better protection to entire unitary body.