Polarity change

Since i just bought an S-Type 3.4 -66 i have read a lot of forums around the net.
There áre many who want to change polarity and have negative earth.
I just wonder: Why?

HI Solbacken,Primarily the Polarity change is made to accommodate the most readily available electronics upgrades.The most common of which is the radio.---Fwiw---Keoke

I have a new radio/cd hidden in my car. With a separate system directly from the battery. So, for that reason a polarity change is overkill.... /ubbthreads/images/graemlins/driving.gif

Besides the radio there are other electrical improvements- I think the most significant may be an upgrade to an alternator with more power. /ubbthreads/images/graemlins/smile.gif

When the old generator dies a natural death this can be a reasonable alternative if you're more concerned with practicality that originality. Of course, it upsets the purists.... /ubbthreads/images/graemlins/frown.gif

But which is more important to you?

Hi James.
You got a point about the alternator. I just bought my S-Type in boxes /ubbthreads/images/graemlins/wink.gif so now i have a golden oportuneity to make thing, just the way i want from the beginning.
The first thing is conversion to Steering Rack.
Maybe polarity change is next.

You might want to think long and hard before you make either change. Everything I have read regarding the change over to Rack and pinion from the current P/S set-up is that it can be a nightmare. While there are a few out there that seem to be OK, there appear to be JUST as many that are having serious issues with camber adjustments, turning ratios and in the end chewing up tyres. Do a LOT of research before you jump into that decision.

As for polarity, I have yet to see any reason for the change over -- other than ease of finding parts. My S-Type came from the factory with a Lucas positive ground alternator which produces more than enough power. Should I need to replace it at some point, I will do like the Austin Healy guys do and get a negative ground alternator and reverse the diodes. In terms of radio and other equipment, they can easily be isolated using non conductive materials including plastic bolts that are obtained from any hardware store.

Webserve

Since most automotive parts these days use negative ground, one of the most beneficial upgrades for an older car is from generator/voltage regulator to alternator and all other factory electical equipment do not care if it is negative or positive (including the starter) I fail to see the aurgument for keeping the positive ground. Other than authenticity, can any one name an advantage? It certainly cannot be a negative ground radio or other accessory that needs ground isolation. If the isolation fails your car might burn up. I highly recommend the negative ground conversion.

/ubbthreads/images/graemlins/savewave.gif Don't wake em up John, let Maude kick em in the Arse.---Keoke-- /ubbthreads/images/graemlins/lol.gif

This is a PS to my previous message. The alternator is a great improvement but if you want to switch the diodes on a new unit to make it positive ground, you have just voided any warranty. Keep it simple.

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I will do like the Austin Healy guys do and get a negative ground alternator and reverse the diodes. In terms of radio and other equipment, they can easily be isolated using non conductive materials including plastic bolts that are obtained from any hardware store.







[/ QUOTE ]

Hmm, /ubbthreads/images/graemlins/nonod.gif I don't know of any Austin Healey people doing things like that and all of my Healeys have been converted to negative ground as well.---Keoke

I certainly did not mean to start a brush fire here BUT!!!!! Now that there seems to be offense taken to my comments, let me just say this.

I am keeping the positive earth on my S-Type because it is indeed of significant historic value. It is 1 of 280 made and 1 of 3 known (of those 280) to still exist. This a $1 will get me a cup of coffee -- but that said, there is a responsibility I feel to keep the car as original as possible -- including positive ground. The car came with a positive ground alternator and after much research, should the original go out on me, I can replace it with a marine alternator which is built positive ground or I can indeed take the advice of the local Healey club and reverse the polarity of a negative earth alternator. https://www.carolinahealeys.com/Technical%20Pages/Electrical/replace_that_lucas_genera.htm

These guys do it so much, I guess, that they put it on their website. I just happen to run into one of the Healey guys who told me it was a pretty easy fix and I was simply passing it along to the list.

Webserve

Thats ok Webserve, but I thought retaining authenticity require maintaining the original parts also. However, those other Healey people you are referring to are out of touch with reality.For example here they are busting their arses over a "35" Amp alternator when a Austin Healey CP42 generator puts out 35 amps and replacing a couple of bearings and the brushes IMOP is simpler than altering an alternator and the engine mounting brackets--- /ubbthreads/images/graemlins/confused.gifKeoke /ubbthreads/images/graemlins/rolleyes.gif

I decided to convert to Negative Ground for two reasons: First because I wanted a modern stereo in my 1965 S type, without having to use any gadgets to isolate it from the positive ground polarity. Second: nobody has mentioned jumping the battery as a reason to go Negative Ground. Let's say your battery died, how are you going to jump-start from one car to another? Chances are that anyone who stops to help will have a Negative Ground vehicle. That
alone is reason enough. But wait there's more: Since converting to Negative Ground, the lights are brighter, the ignition is peppier, the whole car feels energized. Why? I don't know, but it is.

I followed the polarity conversion instructions given by Mike Martinez at Star Auto Electric in California, he rebuilds Lucas generators and alternators. To put it simply, I would not go back to positive ground if you paid me. my only expense was a new battery on the advice of Mike.

Last: how do I make an Avatar?

Hello Exotexs,

there is no difference in using jump leads between differing polarity vehicles, just ensure that they don't touch bodies together.
Whatever made your car seem livlier is nothing to do with the polarity, it makes no difference.

Alec

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I followed the polarity conversion instructions given by Mike Martinez at Star Auto Electric in California,

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Can i find these instruction or similar somewhere on internet?

Solbacken yes, https://www.starautoelectric.com

There are other instructions written by other people in other sites, but they all say to cause a short at the F and B terminals at the generator, and that is not the correct procedure. The Polarity of the generator must be changed at the Voltage Regulator, nowhere else. It was actually very simple.

You will need to reverse the wires at the Coil, and the Ammeter gauge, nothing else assuming other equipment is the original equipment. If the fuel pumps are modern, solid-state pumps, you will have to reverse them too. If the Radio is Positive Ground, get rid of it, install a modern stereo. that's about it. You will need a new battery with the poles in the reversed positions so the original cables will reach. /ubbthreads/images/graemlins/nopity.gif

Piman hello: that's my point. I don't want to have to remember that one of my two Jags is Positive Ground, ('65 S type) and the other is Negative Ground, ('84 XJ-6). Then I would have to remind the mechanic if I ever leave the car with him/her, or anybody else. (but I don't like to). Too much trouble trying to jump a positive ground vehicle with a negative ground vehicle remembering this or that. What if it breaks down when the wife is driving it? She can't tell the difference. Too much room for errors and possible damage. So I decided on consistency and standardization. After all, 95% of cars on planet earth are Negative Ground, so why try to swim against the current?

At least for me, simplicity of maintenance is a priority.
Check this out: there is a company that sells aluminum plates for vintage Jaguar. One of those plates reads: "Warning - the polarity of this car is Negative Ground". I have learned that just like Jaguar made LHD cars along with RHD cars, they also made Negative Ground cars along with Positive Ground cars, depending on the destination market.

If converting to Negative Ground made no difference in the brightness of the lights, or the peppiness of the ignition system after converting, then it must be the new battery, or the fact that whenever the generator is re-polarized, it becomes re-energized.

Hello Exotexs,
your initial post seemed to imply that it was not possible rather than that caution is required. I agree that it can be hazardous if the vehicles are just connected up without looking, but unless I change to an alternator my MK 2 will remain positive earth.

Alec

hello again Piman; yes I implied that jump starting a Pos. Ground car with a Neg. Ground car was not possible, but back then I did not know that it could be done until you said it could, as long as the two cars do not touch. Right there is another good reason to standardize to Neg. Ground, the danger or causing damage to both cars if the cars should touch. Having said that, I understand why some people like you and Webserve prefer to stay with Pos. Ground. In the case of Webserve, his car is one of very few ever made, and there are good reasons to keep it original. In my case, my S type is a driver, (if it is not worth driving, it is not worth having), so converting to Neg. Ground was a necessity for all the reasons. But when you think about it, it makes little difference one way or the other, only at the Coil, the Generator, and the Battery. The rest of the electrical system does not, did not care about the conversion.

I can´t see the problem with positiv ground!
When things work well i don´t see the point.
For me it´s a nice summercar and not for daily use.
I always disconnect battery after a drive with a switch.
The car will not run different with neg, ground.
There are other change to do for that!
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