Vintage Cars: Positive Gounding - Austin Healey, healey, electrics

Question
Dear Jo,

I am a long time owner (40 years) of a 1960 Austin Healey 3000.  I have had extensive experience with repairs, rebuilds, and maintenance of this auto.  However, it has recently come to my attention (after 40 years) that I may have been operated this car at times with a negative ground instead of the preferred positive.  There are many reasons that this could be possible but I will not bore you with the details.  My question---if in fact I did run it with neg vice pos what damage could have occurred?  I have had no problems with the electrical system or performance of the car.

Regards,

Jim

Answer
Hi Jim--

Congratulations on keeping it running this long. Same car as mine (except for my non-original Mk II 3-carb engine), 50th birthday coming up soon!

No 100% guarantee here, but I think I'm right... (any other more knowledgable experts reading?)

As long as you have no electronics (radio, or solid-state things like ignition, fuel pump, voltage regulator), I am pretty certain that the ground doesn't really matter: the basics of 1950-1960s electricity--generator, distributor, coil, condenser--generally work OK backwards. In fact, I ran mine for a few months the wrong way round after a body shop misconnected the battery after a rear fender job.

The main thing I don't know is why the voltage regulator or the starter solenoid would be able to work the wrong way around (solenoid movement), but I had no trouble over those couple of months. My generator has always been pretty feeble, but I don't think the brief excursion into wrong polarity had anything to do with that. (One of these days I'll have it rebuilt).

But if you're thinking of e.g. Pertronix ignition (I highly recommend it), I think you should make it positive like it ought to be. The long cable to the starter solenoid is then negative, and the ignition-switch wire to the coil goes to the negative coil terminal. The positive battery post (which will now be to the rear in the trunk) has just a short cable to the frame. If at some time you have maybe swapped the battery connectors, make them right: they're slightly different diameters for the two posts.

Hey, these are tough basic cars: keep motoring!

Jo

PS If you do have an add-on radio, it is very likely negative ground, in which case think twice about going back to positive ground. (I doubt you can find a positive ground radio these days.)