Hi to alls
My plan is to reverse the polarity of the electrical system on a 1962 Jaguar MK2 (changing from positive ground to negative ground)
The plan is also to change the dynamo by a more powerfull alternator (especially usefull when the engine is running at low RPMs)
What are the detailled steps for implementing this operation ?
Thanks in advance for your help
Gérard

 

I did this many years ago in the mid-80s when I rebuilt a Mark 2. My friend was an automobile electrician and it was so simple to do I was astonished. However I can't remember the exact process, sorry ! I kept the dynamo, so apart from some lead swapping at the instruments, all went OK

If I were you, I'd get the polarity swapped over first with the dynamo, then change to an alternator. The much higher amps generated by the alternator means you would be advised to not pass that current through the ammeter. A lot of people swap to a volt meter that later Jaguars with alternators have.

 

it is simple;
1) First step is to disconnect the battery cables.

this link to Star Auto Electric in California shows how to re-polarize system to Negative Ground.
​​​​​​https://starautoelectric.com/instruc...ing-generator/

As Mitchell says, do it first with the Dynamo / Generator and original Voltage Regulator.

Then, when you install the Alternator, the existing Voltage Regulator will be bypassed, not used, as the Alternator will have its own voltage regulator.

 

You may have to check/modify/swap the fuel pump, depending on which pump you have. Since SU pumps are probably not as reliable as modern Facet or Hardi, you might upgrade anyway. The ammeter will require the connections to be reversed or it will swing the wrong way. If you swap to an alternator, it may be a good time to add some extra fuses to the circuits. Most of this has been discussed in detail in older threads.

 

Peter,
when I converted my '65 S type to Negative Ground, all I did was to reverse the ammeter wires, nothing else other than changing to a modern, negative ground radio.

 

I never could understand what polarizing the generator meant or why it was even necessary ????
Here's a bit copied and pasted from the link above:

"Whenever the battery is disconnected from the vehicle for any reason the polarization procedure should be performed".

Why, I've disconnected and reconnected my battery countless times, and have never done this.

Why does this have to be done when converting from positive to negative ground ?

None of this is directed at you personally Jose, I'm just putting this out there.

Whenever the battery is disconnected from the vehicle for any reason the polarization procedure should be performed.
Whenever the battery is disconnected from the vehicle for any reason the polarization procedure should be performed.

 

Jeff,
no offense taken.

Here's another link to the JCNA website (Jaguar Clubs North America) about converting to Negative Ground / Earth:

https://www.jcna.com/positive-negati...d-conversion-0

essentially same thing as Star Auto Electric about re-polarizing with Dynamo / Generator, except done at the Voltage Regulator.

 

I don't see why it should be done every time the battery is disconnected. This is the first time I've heard it suggested. My guess is that when the polarisation is reversed, it avoids a surge of current on first start up.

 

Peter,
I don't know why either.

I don't like Generators anyway, I prefer Alternators. Not to mention the difficulty of removing the Lucas generator from the pivot bolts.

 

Changing polarity is extremely simple as Jose says.
Simply flash the generator field terminal to positive.
Reverse the wires to the back of the ammeter.
only "traps" are
if somebody has installed an electronic spark ignition system.
polarity conscious fuel pump?
If you have an electric windscreen washer pump you will need to reverse the power leads to the pump.

I have never needed to "refresh" the polarity of a generator. That is old wives tales and BS.
I also believe alternators are better and cheaper when compared to the cost of rebuilding an old generator

 

no question about it. Generators are obsolete.