Identifying system polarity

[Toby]

Despite the high faluting title, my question is simple! It's been so long since the saloon was on the road I can't remember the polarity-positive or negative earth. I know all minors were negative earth but mine has an 8 dynamo conversion complete with regulator, the feed is marked N on the battery terminal whilst the earth has no marking so can't rely on that! I know I could connect it and see whether the ammeter reads correctly or wrongly when current is being used but I don't want to do any damage to the voltage regulator as that was one of the first problems that took the car off the road for fettling 2 years ago and it's not yet back in use! If I connected it up and just tried the starter, without using ignition, I assume it would not turn the engine if polarity was reversed as it would run backwards? Any thoughts? I hope to be at a point, soonish, to start her up.

[Trevor Wilkinson]

Hi Toby.
Everything would work normally whichever way the battery was connected other than the charging circuit (dynamo) If the system had previously been in operation with the polarity reversed the dynamo would not charge, but with the engine not running the dynamo could be re polarised by closing the cut out contacts for a couple of seconds and then pulling them open again. This would reverse the polarity in the field magnets in the dynamo.

[Toby]

So it's ok if the polarity is tried the wrong way round accidentally, to find out??? Sorry but electrics aren't my strong point, I'm not sure what is!

[Trevor Wilkinson]

Yes Toby, no problem at all.
You should not be able To get it wrong though, (famous last words ) as the battery posts, and therefore connectors on the battery cables are different sizes for neg and pos.

[Toby]

Thanks for your sage advice. with regard to the terminal sizes and not getting it wrong...
I refer you to my signature at the bottom of the post!