Subject: [TR] Positive Ground It Is!

From: Jeffrey Gayton <[email-masked]>
Date: Fri, 12 Sep 2014 10:59:29 -0700

Looks like I need a new multimeter. I followed everyone's instructions (and
the manual's as well) and couldn't get a reading of any kind. I wasn't able to
test the meter on my more modern car because the positive lead was sealed up
tight, I'm guessing for safety.

But at Dave's suggestion, I took a closer look at the battery and found
markings behind the posts. I've got a positive earth car! Thanks again for
everyone's help. Now I can order some LED tail lights. Any recommendations
about going with an electronic flasher or LED load resistor. I'm leaning
towards the latter....

** [email-masked] **

Archive: http://www.team.net/archive

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From: Randall <[email-masked]>
Date: Fri, 12 Sep 2014 22:35:50 +0000

---- Jeffrey Gayton <[email-masked]> wrote: 

> everyone's help. Now I can order some LED tail lights. 

Apologies if this is too obvious for words: Now would be the time to consider whether you want to stay opposite to the rest of the world or convert to negative ground.  We're fortunate to have Litezupp that makes positive ground LED bulbs; but the vast majority of aftermarket accessories are strictly negative ground.  Even just adding an outlet to charge your cell phone is extra hassle with positive ground.

I once saw a buddy burn up the wiring harness in his MGA, because it didn't occur to him that the CB radio he had borrowed had a (negative) ground path through the antenna clamp.  It worked at first, because the bumper bolts were too rusty to conduct.  So we were hundreds of miles from home when the one of the bolts rubbed through the rust and the cockpit filled with smoke rolling down the freeway.  You might say it made an impression on me!

The conversion from positive to negative ground is pretty trivial on the TR2-4.  Just swap the wires at the coil, ammeter and battery; then repolarize the generator.  If you forgot to swap at the coil, you'd probably never notice the difference.  And if you forget to swap at the ammeter, it just reads backwards.

Repolarizing the generator sounds scary, but it's trivial as well.  Just pull the wire off the 'F' terminal at the control box, and brush it against the 'A' terminal next to it.  You'll see some small sparks to tell you the connection was made.  Then put the wire back on 'F', close the hood and take a drive.

- Randall

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From: Jeffrey Gayton <[email-masked]>
Date: Mon, 15 Sep 2014 08:55:38 -0700

Thanks, Randall. As you've probably gathered from some of my posts, nothing is
too obvious for me at this stage!

> On 12 Sep 2014, at 3:35 PM, Randall <[email-masked]> wrote:
>
>
> Apologies if this is too obvious for words: Now would be the time to
consider whether you want to stay opposite to the rest of the world or convert
to negative ground.  We're fortunate to have Litezupp that makes positive
ground LED bulbs; but the vast majority of aftermarket accessories are
strictly negative ground.  Even just adding an outlet to charge your cell
phone is extra hassle with positive ground.
>
> I once saw a buddy burn up the wiring harness in his MGA, because it didn't
occur to him that the CB radio he had borrowed had a (negative) ground path
through the antenna clamp.  It worked at first, because the bumper bolts were
too rusty to conduct.  So we were hundreds of miles from home when the one of
the bolts rubbed through the rust and the cockpit filled with smoke rolling
down the freeway.  You might say it made an impression on me!
>
> The conversion from positive to negative ground is pretty trivial on the
TR2-4.  Just swap the wires at the coil, ammeter and battery; then repolarize
the generator.  If you forgot to swap at the coil, you'd probably never notice
the difference.  And if you forget to swap at the ammeter, it just reads
backwards.
>
> Repolarizing the generator sounds scary, but it's trivial as well.  Just
pull the wire off the 'F' terminal at the control box, and brush it against
the 'A' terminal next to it.  You'll see some small sparks to tell you the
connection was made.  Then put the wire back on 'F', close the hood and take a
drive.
> - Randall

-- Jeff