Lotus Elan

Positive Earth vs. Negative Ground

PostPost by: dfysh » Sat Nov 26, 2005 2:13 pm

I am about to send my tach off to Nosinger to convert it to work with
electronic ignition. Is there any compelling reason to do the switch to
negative ground too? Other than the fact that the tach could be converted
at no additional cost why would I want to go to the trouble to convert the
rest of the electrical system? Everything else electrical is working well
right now.



Thanks,



Don

S3/5607
dfysh
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PostPost by: Benjamin Levy » Sat Nov 26, 2005 3:00 pm

On 11/26/05, Don Fysh <***@***.***> wrote:
I am about to send my tach off to Nosinger to convert it to work with
electronic ignition. Is there any compelling reason to do the switch to
negative ground too?

Does your electronic ignition work with positive ground?
---Ben Levy
Benjamin Levy
 

PostPost by: dfysh » Sat Nov 26, 2005 3:34 pm

The electronic ignition will work with positive ground but if I ever want to
switch to negative later I will have to modify the tach to suit.

Don
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PostPost by: TYPE45 at aol.com » Sat Nov 26, 2005 8:25 pm

Don,

If you ever decide to install/replace a radio in the car, your options will
be severely limited if you restrict yourself to positive ground radios.

Also, my experience with Nisonger is that they can fix all of the other
gauges, but they cannot convert a Smiths tach to work with an electronic ignition
system. After sending mine back twice with no luck, I gave up. Nisonger would
not voluntarily return my money, so I had to go to Visa in order to get my
money back.

They charge more than Nisonger, but APT Instruments (The Gauge Guys) can do
the job. Problem is, the guy who owns that company is not the kind of person
anyone would want to do business with.

I came up with a third alternative. I went to the junkyard and yanked a tach
from a modern Japanese car. The difficult part was that I had to make up two
adapter plates so that the original needle, housing, and face could be
retained. I am pleased with the results. Hope you can use this information.

Frank Howard
'71 S4 SE
Minnesota
TYPE45 at aol.com
 

PostPost by: Lincoln62 » Sun Nov 27, 2005 11:46 pm

I switched mine to neg earth 20 years ago so I could get the stereo to
work. My auto electrician told me how to do it and I did it myself, I
remember it being really easy but can't remember the exact details.
Pretty sure I didn't have to change polarity on any of the gauges.

Cheers
Peter 66S2

Don Fysh wrote:

I am about to send my tach off to Nosinger to convert it to work with
electronic ignition. Is there any compelling reason to do the switch to
negative ground too? Other than the fact that the tach could be converted
at no additional cost why would I want to go to the trouble to convert the
rest of the electrical system? Everything else electrical is working well
right now.
User avatar
Lincoln62
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Location: Sydney, Australia

PostPost by: dfysh » Mon Nov 28, 2005 2:04 am

Thanks for the input. I think I will go ahead with the switch. The radio
choices is a big factor. Right now I have a duff radio filling the slot in
the dash because I couldn't find a replacement with positive polarity.

Is there any place where I can find guidance on how to make the switch to
negative ground?

Don
dfysh
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Joined: 03 Jul 2005

PostPost by: c.beijersbergen » Mon Nov 28, 2005 8:52 am

Why bother with a switch from positive ground to negative ground if it is only for a radio set. Every radio set needs a plus and a minus power connection. The minus connection most often is connected to the metal housing of the radio. In a metal car with positive ground this can cause a problem, but an Elan consists of polyester and wood only in the dashboard area.
In the car a plus connection is available and a minus signal as well. The plus happens to be connected to the chassis.
So simply connect the plus and the minus of your radio to the plus and the minus of the car. As long as the radio housing does not touch the chassis or any other grounded part of the car it will work fine.

Cor Beijersbergen van Henegouwen
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PostPost by: "Brian Goodison" » Mon Nov 28, 2005 12:03 pm

Another reason to change to a negative ground would be if at some
stage you wanted to replace the generator with an alternator.
Brian
64Elan/72Sprint/Birkin T.C.Seven

In ***@***.***, "C. Beijersbergen"
<[email protected]> wrote:
Why bother with a switch from positive ground to negative ground if
it is only for a radio set.
"Brian Goodison"
 

PostPost by: TYPE45 at aol.com » Mon Nov 28, 2005 6:11 pm

Cor,

I hate to criticize, but I think an owner is making a big mistake simply
connecting the positive lead from the radio to ground and the radio chassis to
positive. The ground connections throughout the car are usually open to contact
and not insulated. On the other hand, the positive connections should be
completely insulated so that a direct short cannot be created if anything that is
grounded comes into contact with it.

I know you provided a disclaimer that said "As long as the radio housing does
not touch the chassis or any other grounded part of the car it will work
fine," but there is too great a chance of that happening. For instance, right
above the radio on my car are the cables for the heater and the choke. They are
both grounded to the engine and if they came into contact with a hot radio
housing, they would create a direct short. The radio housing, in your
application represents a big, uninsulated positive connection. As these cars already
have a reputation for spontaneous combustion, adding a hot uninsulated radio
housing cannot help. I just don't think this is a good idea. Just my opinion
though. Hope I wasn't too hard on you.

Frank Howard
'71 S4 SE
Minnesota
TYPE45 at aol.com
 

PostPost by: "Stan Aarhus" » Mon Nov 28, 2005 6:31 pm

I switched to negative ground years ago and since I didn't have a radio, my only concern was the tach. Since it was totally isolated, I swapped the ground and power lead and had no problems. I agree that the radio area has lots of possibilities for shorts, and would hesitate to try swapping the connections in that area. I plan to use a Mini-DIN format radio. which will fit if the main loom is flattened a bit to fit under the radio. I plan to use a sheet of thin nylon between the radio bottom and the wire flattened wire harness. As to the tach, I plan to do the polarity swap mod on it as well, just for consistency sake.

Stan
66 Elan Coupe' (will be done RSN)
64 Elan Roadster ( awaiting attention)
"Stan Aarhus"
 

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