by Ed Esslinger in the May 1998 RootesReview

At the SOS Roundup last year, I was asked how to change an Alpine to negative ground. I have a series III Alpine I wanted to change polarity on, so I decided to come up with a step-by-step procedure that only applies to Sunbeams Series I, II, Ill and IV.

Some things that must be investigated before you start:

  • Do you have a positive ground tach (Series IV)?
  • Do you have a positive ground radio?
  • Do you have any other positive ground devices in your car?

Step by Step

  • Disconnect and remove battery. On Series IV disconnect and remove tach.
  • Replace the original negative connector with a good battery connector of the universal type.
  • Replace the original positive cable with a good braided type ground cable, 9 inches long
  • Replace battery, connect negative side to ground cable, connect positive side to new universal connector.
  • Disconnect the field wire from the regulator (yellow/ green) on Series I and II (brown/ green) Series Ill and IV
  • Momentarily (2-3 seconds) touch the disconnected field wire to the battery side of the starter solenoid. This polarizes the generator to negative ground.
  • Reconnect the field wire to the regulator.
  • On the ignition coil, reverse the primary wires. + or CB should now be hot, with the ignition switch on; – or SW should now be connected to the distributor.
  • If an ammeter is installed, the connections will need to be reversed at the meter or elsewhere.
  • The first nine steps are all you really need to do on a Series I, II, Ill, but see note on regulator polarity.
  • On a Series IV, the tach polarity must be changed or a Series V unit can be used.
  • On a Series V, the tach pick up loop must be wound in the opposite direction.
  • Information on steps 11 and 12 can be found in other sections of the Sunbeam Survivor

Notes:

While I was researching this project, I found that regulators are polarity sensitive.

Regulator polarity: Most regulators are designed for use with systems having the negative terminal grounded. Using the wrong polarity regulator on a system will cause the regulator contacts to pit badly and shorten its life. It also states that transfer of metal and arcing of the contacts will be greatly increased, resulting in shorter contact life.

Armatures and stationary contact brackets of all positive ground units are cadmium plated. Armature and stationary contact brackets of negative units are copper plated. (From Goodheart Willcox Automotive Encyclopedia). I have used Lucas regulators in the past with the car changed to negative ground without problems, but after reading the above, I decided to use a regulator for a ’64 Ford. As the Lucas generator and Ford generator both have their field grounded internally, the negative ground Ford regulator should work fine. If you decide to use a Ford regulator, you will need to make an adapter plate to mount it. Also, the spade type connectors will have to be changed to mate with the Ford regulator. The connections for Series I and II are: brown and brown/ blue to battery; yellow/green to field; two yellow wires to armature. The connections for Series Ill and IV are: brown/ green to field; brown/ yellow wires to armature. Discard black wire; make sure that regulator has a good ground on the car.

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