Tips on converting to negative ground

September 1, 2009 | By Richard Prince


I am a subscriber to Auto Restorer and want to commend you for going back to full color editions. It is much easier to follow and understand the photos of restoration projects, particularly those that include wiring.

On that subject, I have a question that I hope you might be able to answer. I have a 1962 Austin-Healey 3000 MK II that I restored. The car, as you may know, has a positive ground. I would like to install a modern radio in the car and would like to know how to go about this without burning up the radio or damaging the car’s electrical system.


There are several ways to solve your problem but the most sensible may be to convert your Austin-Healey to a negative ground setup. Besides accommodating a new stereo, converting to negative ground would also enable you to utilize other modern electronics, such as a charger for your mobile phone, etc.

Converting to a negative ground is relatively simple. After disconnecting the battery, reverse the wires on the ammeter and ignition coil. Reconnect the battery cables on the opposite terminals so that the negative post is the ground, and then polarize the generator for negative ground. The polarity of the generator is determined by the direction of the most recent current through its field windings. To polarize your generator, use a jumper wire to momentarily connect the battery connection to the generator connection on the voltage regulator.