Neg to Post Earth & Back Again

[fastfrontier17]

Hi all,

Just wanted to ask a quick question.

When I got my car, the battery was hooked up such that it was positive earth, however, there was a note in the bottom of the tray that said the car had been converted to negative earth. I found this note when I went to replace the battery with a fresh one, and after finding it I hooked the new battery up to negative earth. My question is, are there any detrimental effects from converting positive earth to negative earth, returning it to positive earth, and then back to negative earth once again? I have no idea if the polarity of the generator was changed the original time or not, and not sure how to check at the moment without having researched.

 

[jumpinjan]

Only two things that I remembered: Re-polarize the voltage regulator and reverse the leads on the ammeter. Some vintage radios had a polarity switch too.
Jan

 

[doggone03]

Hi all,

Just wanted to ask a quick question.

When I got my car, the battery was hooked up such that it was positive earth, however, there was a note in the bottom of the tray that said the car had been converted to negative earth. I found this note when I went to replace the battery with a fresh one, and after finding it I hooked the new battery up to negative earth. My question is, are there any detrimental effects from converting positive earth to negative earth, returning it to positive earth, and then back to negative earth once again? I have no idea if the polarity of the generator was changed the original time or not, and not sure how to check at the moment without having researched.

I tried changing the polarity on my Series IV from positive earth to negative earth and found the impulse tach wouldn't work. Back to positive earth and the tach works again. While playing around, I did fry out my voltage regulator and bought a replacement at SS. I found a 1970's vintage radio with a negative/positive switch on the back and now I have a working radio. Most of the time the radio is off while I'm tuned into the engine sounds. If everything works while running positive ground, be happy and move on to the next Sunbeam quirk - it's all part of the fun.

 

[mxp01]

When I converted to negative earth on my SIV I had to have my impulse tachometer converted to negative earth. At the time I was also still running the generator with the external voltage regulator. This was many years ago when I converted, but I believe I had to repolarize the generator, convert the tach (as I stated above), and reverse the leads on the ammeter. I'm sure I have forgotten some steps, but there are previous threads with step by step directions.

It wasn't long after going to negative earth that I converted to an alternator.

 

[fastfrontier17]

So with my ammeter hooked up for positive Earth, if if I turn the lights on it should show it as charging, and if the car is running and generator is charging it should show it as discharging, correct? Trying to ensure that the polarity of the generator was reversed by the PO. It also has a pertronix ignitor, not sure how that wiring is supposed to be reversed.

 

[BEpine]

The Pertronix Ignitor is sold as positive or negative earth. It cannot be reversed. If it gets the wrong polarity, it's fried.

 

[hartmandm]

Jaguar clocks guy told me the original Smiths clocks that are positive ground will be fried if you reverse the polarity to the clock.

Mike

 

[mxp01]

This link will tell you how to re-polarize the generator. Also check how your coil is wired.

https://www.askthemechanic.co.uk/classic-cars/sunbeam-alpine/negative-earth

 

[fastfrontier17]

The Pertronix Ignitor is sold as positive or negative earth. It cannot be reversed. If it gets the wrong polarity, it's fried.

Still works after I swapped it back from positive to negative again