positive to negative earth

[Timothy Keith-Lucas]

Is there discussion in any known location of the pros and cons of converting an early Seven from positive to negative earth? I keep struggling with finding positive earth parts for my 1962 S2, and keep being tempted to try it. Could work, and could be a very expensive failure. Thoughts?

[wdb]

I'm contemplating the same for a 1967 Lotus Elan. I've been told it's pretty straightforward. One tricky bit on that car is the tach, which is electronic and needs to be the correct ground. I would replace the generator altogether in my case. If originality is important they make alternators that look like generators.

[7Westfield]

Been 50 years ago, but I switched my Bugeye over. Not too much hassle

I used some japanese alternator, but it is possible to reverse the polarity of a generator

Got a tach from a Fiat    you can have them converted, but pricey

don't recall if fuel gauge  needed anything

I THINK the wiper motor was ok

switch coil wires around   electric fuel pump?

starter doesn't care

if you have one of the Lucas "voltage stabilizers" for the gauges, a neg ground unit is cheap from Moss

[Jbrueckh]

If you get a tach conversion kit from Spiyda in the UK, it’s easy to do. I did it this winter on my 67 Elan.  I did it because I switched to all LED lighting and a Suzuki samari alternator. 
https://spiyda.com/tachometer-electronics.html

[SENC]

The old se7ens.net mailserve is all but dead, but it is still out there and if you can join you can search old threads.  That would likely be the best source of specific information.  If you can't join and want, I can try to search for you.

[Timothy Keith-Lucas]

Thanks, SENC. I've found a few general guides, such as https://blog.simonbbc.com/classic-car-projects-and-tips/converting-a-vehicle-from-positive-earth-to-negative-earth-electronic-ignition/. I will try to learn to do searches on USA7s, because I should know how to answer some of my questions that way rather than asking knowledgeable members to repeat stuff they wrote years ago. If I fail, I hope you won't mind guiding me into it.

[wdb]

Here's information for a Lotus Cortina conversion, may be helpful.

 

https://www.lotus-cortina.com/electric/convert.htm

 

 

[SENC]

TLK - here are a couple threads from the se7ens.net mailing list that popped up when I searched the archives... you may find something useful.  So far I've kept mine positive earth, just haven't found any good reason to change it.

 

________________

 

I changed the polarity on my seven because the rev counter I was going to
use required it. All you have to do is repolarise the dynamo by just
touching 12 volts from the battery across the field coil in the opposite
direction.(and after you must connect the battery the other way round of
course) This changes the residual magnetism in the unit and means that the
current starts in the opposite direction when it just starts working. This
current energizes the field coil with the field reversed and the unit works
the other way. The field coil is between the small spade terminal on the
dynamo and the body (ground). The opposite direction means that whatever
ground you wish to have is connected to the body and the 'live' is touched
onto the spade terminal a couple of times -just flicked over the surface.
Job done! Since it is unbelievable is could be that simple, check it with
your voltmeter before connecting it back into the cars wiring.

-----Original Message-----
From: JF
Sent: Wednesday, September 17, 2003 5:28 PM
To: lotus at se7ens.net
Subject: [Lotus] Lucas electrics, alternator conversions and positive
ground


I have to agree with JWW. We should leave the electrics as original as 
possible.
While I understand the advantages of alternators, I enjoy watching the 
lights dim and brighten with the revs. It's further conformation that 
all is working correctly.

The only area I'm considering changing on my Series 2 Seven (1965) is 
reversing the positive ground. And, here's why.
A year ago I acquired an exhaust gas analyzer instrument which I've been 
told is the best route to figure the optimum jets on Webbers at various 
loads. Better than a rolling road I've been told. The problem is the 
instructions say it only works with a negative ground systems.

Has anyone else changed from positive to negative ground on a Series 2?
And if so, how did you do it and were there any problems?

Jeremy
SB2097


jww wrote:

><rant> I have two Sevens using all Lucas electrics. Both have 
>dynamos and regulators and thus far (in 3 years) I haven't 
>had a single problem. I use Lucas electics because that is 
>the original equipment for the car.
>
>IMHO I find that electrics in most restored Lotus Sevens 1957 
>to 1973 have been badly re-installed during the restoration 
>process. Wiring should be neat and tidy and not like a 
>plateful of spaghetti behind the dashboard. The taped loom 
>should pass along and the various tails should just neatly 
>bridge from the loom to the relevent connection, usually a 
>matter of two or three inches. With that done problems are 
>easier to locate.
>
>I find all the Lucas electrical products in my cars are 
>totally reliable with the possible exception of the dynamo to 
>engine bracket on my Series Two which is a Ford item anyway. 
>Lucas have made electrical components for a great number of 
>British car manufacturers for the best part of a century. All 
>these companies cannot possibly be wrong!!
>
>The relatively small amount of electrical equipment in early 
>Sevens causes a comparatively light load on the battery if 
>installed properly. Unless you're  planning the addition of 
>air conditioning, a 100 watt hi-fi and uprated headlights and 
>want these all on at the same time, you really don't need to 
>run an alternator. However, you would be prudent to regularly 
>check your battery levels and plug into a battery 
>conditioner. Remember most electrical problems on Sevens are 
>due to bad earthing.
>
>If you want a modern Seven, then get a Caterham, Westfield, 
>Locost, Robin Hood, or whatever. If you want the genuine 
>article, a Lotus Seven built in the 1960s, then why not run 
>it as they used to. As I've said, I've never had a problem. 
>Boy do you guys love 'improving' what are now 30 to 46 years 
>old and are after all classic sportscars. Be proud of them 
>and their idiosyncrasies!!!</rant>
>
>Cheers,
>
>JWW.      

_______________________

 

Hi all,

I agree with Flemming. Original Series Two had mechanical 
Water Temp and Oil Pressure, just leaving Tacho if electric, 
swapping the wires over on the Ammeter and the dynamo 
ofcourse. Series One and America models used mechanical tachos
which means just two jobs. Series Three and Four models were 
negative earth from the factory and I can't think of a single 
reason to change this! 

However one other thing: the earth side of the battery wants 
to be the forward post for clearance of the bonnet otherwise 
sparks will fly, so if you are changine polarity this should 
be remembered!

Just my penn'th!

JWW

(snip)
<<< There is no real good reason to convert back to a 
positive ground, unless you want your car to be as 'British' 
as it was when it left the factory.

However, it is not as difficult as it may seem.

Polarizing the generator is pretty simple, and can be done in 
about fifteen minutes, without even removing the generator 
from the car.

Voltage regulator is not affected by a polarity change.

Starter will turn the right direction with either polarity, 
so no rewiring is needed.

An electronic tachometer will need to have the internals 
rewired for the correct polarity, but a mechanical tachometer 
will never know the difference.

If you have an electrical temperature gauge, oil pressure 
gauge, or a fuel gauge, you will need to replace these, but 
mechanical gauges will not be affected.

Finally, if you have an ammeter, as originally fitted, you 
will need to switch the two wires on the back of the meter, 
or get used to the meter reading reverse of normal.

The rest of the electrical equipment, e.g. lighting, horn, 
coil and distributor, etc. will not require any rewiring, but 
if you have an electronic ignition system, it will have to be 
replaced or rewired for the correct polarity.

Electricity is pretty simple, if you know how it works, but 
if you don't, it is better to leave it alone, or to hand it 
off to someone who does.

And remember the old rule: "If it works, don't try to fix it."

-- Flemming >>>