• From: Ventura, CA
  • Registered: 2010-12-10
  • Posts: 32

Topic: What to do about a positive ground electrical system?

In doing research on our Lemons car that we go to pick up saturday I was delighted to see the old crap bucket uses a 12v electrical system (as far as the internets lead me to believe), but then found out it is listed as a positive ground electrical system. I immediately went to the rules and rule 3.14.1 says all "hot" terminals must be insulated. Just so we don't have to worry about this when we're in tech, the negative terminals would be the "hot" terminals on a positive ground system?

I hope someone is less confused than me about this.

And yes, I am thinking about converting the thing to negative ground, but then we will have to make the starter and distributor do crazy things.

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  • From: Aumsville, Oregon (Near Salem)
  • Registered: 2010-08-22
  • Posts: 1,913

Re: What to do about a positive ground electrical system?

Markstre302 wrote:

In doing research on our Lemons car that we go to pick up saturday I was delighted to see the old crap bucket uses a 12v electrical system (as far as the internets lead me to believe), but then found out it is listed as a positive ground electrical system. I immediately went to the rules and rule 3.14.1 says all "hot" terminals must be insulated. Just so we don't have to worry about this when we're in tech, the negative terminals would be the "hot" terminals on a positive ground system?

You are absolutely correct.

Markstre302 wrote:

I hope someone is less confused than me about this.

You are not confused at all.

Markstre302 wrote:

And yes, I am thinking about converting the thing to negative ground, but then we will have to make the starter and distributor do crazy things.

Why would you want to convert to negative ground?   The only reason to do so would be if you were adding equipment that required a negative ground system.   Examples might be: electronic ignition, some radio systems, tachometer, etc.   If you are not using something that requires negative ground, leave it alone but label it clearly and make sure everyone working on the car knows it.

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  • Serj
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  • From: Cincinnati, OH
  • Registered: 2009-05-02
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Re: What to do about a positive ground electrical system?

just make sure you coat all the sheetmetal in rubber. big_smile

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  • From: Douglas Flat, CA
  • Registered: 2010-01-08
  • Posts: 172

Re: What to do about a positive ground electrical system?

Markstre302 wrote:

...And yes, I am thinking about converting the thing to negative ground, but then we will have to make the starter and distributor do crazy things.

You should call that Geordie guy over from Star Trek. He seems to reverse the polarity on everything he touches.

But seriously, when I converted my Spitfire to negative ground, it took about 20 minutes to just move a bunch of wires around. That is, besides the time it took to install the internally-regulated GM alternator. The starter didn't care since it had an electromagnet field, and not a permanent magnet field. The distributor had mechanical points and never knew the difference.

  • From: Redwood Estates, CA
  • Registered: 2010-08-10
  • Posts: 201

Re: What to do about a positive ground electrical system?

I don't think it is as hard as you think, I converted a 12v Morris Minor to negative ground, all it took was to run the generator like a motor to reverse the polarity. Now, maybe you car has an alternator? Then I don't know, but otherwise, the rest of the car doesn't care.

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  • From: Boulder, CO
  • Registered: 2010-11-12
  • Posts: 602

Re: What to do about a positive ground electrical system?

If it has a positive ground then it likely has a generator, not an alternator.

If you end up wanting/needing to convert over to an alternator (cheaper to replace, more common, more reliable) you'll likely have to convert to negative ground as positive ground alternators are rare and expensive.

As others have said, it's easy to do.  I did it on my Amphicar and the only hard part is rewiring/recalibrating the stock fuel gauge - which you likely won't need to worry about (particularly if you use a fuel cell).

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  • From: Columbus, OH
  • Registered: 2009-05-26
  • Posts: 2,839

Re: What to do about a positive ground electrical system?

sublimate wrote:

I did it on my Amphicar

This is not something you will read in most forums.  Alvis bless Lemons.

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  • From: The other side of the fence
  • Registered: 2009-06-17
  • Posts: 388

Re: What to do about a positive ground electrical system?

To do a conversion on a early car is not that hard if you are not using interior and dash lights. Disconnect your generator charge wire and your starter main power wire then reverse the battery cables. Then strike the generator charge pole with your charge wire and make it spark a few times. this will polarize your generator to positive. hook the starter back up. If it is a point distributor it wont care either way and should work fine. You may have to adjust your voltage regulator to make it put out the correct voltage but that is about it.

Pen

  • From: Columbus, OH
  • Registered: 2009-05-26
  • Posts: 2,839

Re: What to do about a positive ground electrical system?

Light bulbs don't typically care which end is positive and which is negative, do they?

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  • From: Gilbertsville, PA
  • Registered: 2009-12-22
  • Posts: 3,251

Re: What to do about a positive ground electrical system?

dculberson wrote:

Light bulbs don't typically care which end is positive and which is negative, do they?

negative

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  • From: Cincinnati, OH
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Re: What to do about a positive ground electrical system?

positive?

  • From: Boulder, CO
  • Registered: 2010-11-12
  • Posts: 602

Re: What to do about a positive ground electrical system?

I think they care, they just don't show it.
Inside they're crying while outside they're shining just as bright as ever.

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  • From: Sacramento
  • Registered: 2010-08-09
  • Posts: 1,665

Re: What to do about a positive ground electrical system?

When you switch from plus to minus there is one commonly overlooked, but usually not functional in Lemons item that kinda cares: the heater blower. If hooked up backwards it still spins but little-to-no air comes out 'cause the fan is going the wrong way.

Remember, if one item of your car is going the wrong way, many other parts will follow shortly. This is part of the self-righting sticker law.

~in the case of BazAckwardz, almost all items are wrong way in a complete subset of parts (Chassis vs Coach) so it's less likely to be self-wrong way generating, about normal percentages...

  • From: Houston (Spring) Texas
  • Registered: 2010-02-22
  • Posts: 1,624

Re: What to do about a positive ground electrical system?

dculberson wrote:

Light bulbs don't typically care which end is positive and which is negative, do they?

Filiment, no
LED, yes (but your car probably didnt have any LEDs from the factory)

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  • From: Columbus, OH
  • Registered: 2009-05-26
  • Posts: 2,839

Re: What to do about a positive ground electrical system?

Especially not if it's old enough to have a positive ground.

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  • From: Land Of Subarus, Colorado
  • Registered: 2009-04-30
  • Posts: 9,416

Re: What to do about a positive ground electrical system?

Just the fact that we're going to have a positive-ground car in Lemons is enough to make me happy.

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