How to convert from positive to negative ground?

[Magyar]

Is there a thread or write-up regarding how to convert from a positive ground to a negative ground Spridget? I have a 62 MKII Sprite and would like to do the conversion but I am out of my comfort zone when it comes to electrical work. As said by several, the purpose of owning the Sprite, aside from the fun of it, is the educational value. My first question on this venture is why were they set up with a positive ground in the first place?

Thanks, Magyar

 

[Billm]

Try this one:
https://www.britishcarforum.com/bcforum/u...rsio#Post559997

Bill

 

[jvandyke]

I just converted my '63. Reason for + ground in the first place? No reason I don't think, makes no difference. - ground has become the standard so that's the way they are just for uniformity. Most all devices are set up for - ground now a days so if you want a stereo or any newer gadgetry -ground makes life simpler.
Conversion is easy really, re-doing the tach is probably the hard part, unless you've still got the mechanical one running off the dynamo yet? I think that was BE only thing. I think if you search here you'll see my tach conversion pictures somewhere, or I'll post 'em again if you want.

More links for fun
https://mgaguru.com/mgtech/electric/et202.htm
https://www.mgcars.org.uk/midgetspriteclub/MascNew/TechTips/PosNeg.html

And here's the tach convert picture anyway.

Do that, switch the wires at the loop on the back and tach is done.

 

[Sarastro]

Do an internet search; there are lots of descriptions on doing this, some better than others.

Good question about how the positive-ground standard originated. I suspect it simply came from a time when there really was no consensus on this, and no good reason to go one way or the other. So, it was largely a case of doing what people nearby were doing. Today, there are good reasons for negative ground, related to the fact that this is essential for modern transistor electronics. Back in the days of tubes and early transistors, it wasn't so important. I can get into the details of why this is, if you wish.

 

[Roger]

Remembering, as I do, when the change to positive ground was much discussed in the UK, I believe the manufacturers did it to reduce battery terminal corrosion.
That, at the same time, they increased body corrosion was of little apparent interest.

 

[AUSMHLY]

Hello Magyar,

Here's a link to Hendrix Wire Wheel, who shows in detail how to convert a positive to negative.

Good luck,
Roger

 

[ichthos]

I was interested in converting to a negative ground also - I remember asking the same question a while back. This type of work is out of my comfort zone too. Besides the reasons mentioned, one of the reasons I didn't see listed is that if one were to get a jump start, it could make it confusing and dangerous if both parties involved do not readily see it is a positive ground. I am still considering the conversion once I get my car back together. It would be great if you could post your results when you finish.

Kevin

 

[jlaird]

Instruction on how to polarize a Generator:


In all the years I have been in business, I have heard many versions on how to polarize a generator and voltage regulator. Some versions are correct, others are totally wrong.
Polarization is a procedure which matches the polarity for the generator and the voltage regulator. The majority of the vehicles are manufactured negative ground although some of the older vehicles were manufactured positive ground. The generator has to be set up for either polarity. The generator will charge either way, however the voltage regulator has only one polarity. Whenever the battery is disconnected from the vehicle for any reason the polarization procedure should be performed.
The recommendation on how to polarize a charging system is the following: After the installation of a battery, generator or voltage regulator follow these procedures. The terminals on the voltage regulator are labeled with letters and this is where you will do the polarizing procedure. Both of the components will have battery power so do not start the vehicle or turn on the ignition switch before polarizing them. You will need a small piece of wire fourteen or sixteen gauge with alligator clips on the ends. Find the "B" terminal on the regulator and attach one of the alligator clips, find the "D" terminal and touch the terminal with the other alligator clip. You can touch the terminals a few times and it will produce a soft light spark. Under no circumstances touch the "F" terminal or any other part of the regulator or you could damage the regulator.
For the Lucas voltage regulators that have the teminals labeled A1, A, F, D, E, the polarization procedure is the same however the terminals that will be used are the "D" terminal and either the "A" or "A1" depending on which teminal is used on the vehicle. Either terminal can be used if wires are going to both terminals.
Start the vehicle and you should see the red generator light go off on the instrument panel, you may have to rev the engine up a few RPM, generators have a tendency not to charge at idle speed. If you have a gauge on the instrument panel the gauge will respond accordingly.
Look for more technical information in the future on these page.

Sincerely,
Mike Martinez


https://www.starautoelectric.com/Technical.htm

 

[Hairyone]

It's all explained here: https://www.mgcars.org.uk/midgetspriteclub/MascNew/TechTips/PosNeg.html

 

[AUSMHLY]

Besides the reasons mentioned, one of the reasons I didn't see listed is that if one were to get a jump start, it could make it confusing and dangerous if both parties involved do not readily see it is a positive ground.
Kevin

Hello Kevin,

It is up to the owners to inform that they have a postive car before jumping.

If one car is postive and the other is negative, just make sure the two cars do not touch each other.

Jumper cable clamps to:
Positive post of one battery to postive post of the other.
Negative to negative.

Cheers,
Roger

 

[Sarastro]

Problem is, there are a lot young of car-service people out there who don't know that positive ground ever existed. And, no matter what precautions you take, there is still a very real chance someone could hook it up wrong. There's a fundamental engineering principle here: the more you make things the way people expect them to be, the less chance of something getting done wrong and the resulting damage or accident.