Lotus Elan

1968 postive ground?

PostPost by: LotusNWT » Fri Jul 03, 2009 3:09 am

I have a 1968 plus two #644 I beleive and I have many electical gremlins. gauges that don't work, a non charging generator etc. A rather experienced retired volvo mechanic (who when in Britain worked on rovers) took a look at my car and thought the positive ground set up look odd. He though someone may have changed it to positive ground not knowing what they were doing. (The car had all these problems when I bought it and the last owner fully disclosed them). Does anyone know should it be positive or negative ground???

Thanks for any help
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PostPost by: RichC » Fri Jul 03, 2009 4:31 am

positive ground.
I had a similar problem which was solved by running a separate earth cable ( a decent cable probably abt 5mm outside diameter)from the positive terminal to the bunch of black wires (earth leads) which all interconnect under the dash, rather than relying on the troublesome earth connection to the chassis on top of the transmission tunnel just behind the dash.
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PostPost by: LotusNWT » Sat Jul 04, 2009 2:29 am

Thanks...so it should be positive ground, the ground may just be troublesome.

Glen
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PostPost by: bcmc33 » Sat Jul 04, 2009 9:45 am

Positive or negative ground (earth) is always a major issue with any plastic bodied vehicle.

Whenever there is an electrical problem - the first thing to check is the grounding continuity.

75% of all my electrical problems have been down to poor grounding.
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PostPost by: rgh0 » Sat Jul 04, 2009 10:29 am

I thought all Plus 2 from the beginning were negative earth.

regards
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PostPost by: monoposto » Sat Jul 04, 2009 6:24 pm

Mine was originally positive earth - it should be written on the bottom of the tacho face. Mind you, if it has been converted, the tacho would probably have been changed as well.

Lee

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PostPost by: paddy » Sat Jul 04, 2009 7:04 pm

monoposto wrote:Mine was originally positive earth - it should be written on the bottom of the tacho face. Mind you, if it has been converted, the tacho would probably have been changed as well.


According to Robinshaw and Ross, -ve earth was introduced at chassis no 0857 for Federal models and 1087 for all other models.

I think the tacho would typically be converted with a modiifcation to the internals without changing the unit.

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PostPost by: rgh0 » Sun Jul 05, 2009 12:20 am

Hi Paddy - I learn sometinhg new every day - where is it in Robinshaw and Ross - cant find it in my copy - in fact cant find anything on Plus 2's - was there a later edition with plus 2 information ?

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PostPost by: aussieelan » Sun Jul 05, 2009 5:13 am

The info Paddy posted (attributed to Robinshaw and Ross), correlates with the info on Trevor Sparrows excellent Plus 2 site.

Also correlates to #763 ... was originally positive earth, changed to negative at the same time the generator to alternator conversion was done.
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PostPost by: paddy » Sun Jul 05, 2009 7:01 pm

rgh0 wrote:Hi Paddy - I learn sometinhg new every day - where is it in Robinshaw and Ross - cant find it in my copy - in fact cant find anything on Plus 2's - was there a later edition with plus 2 information ?


Yes, there was a later edition with chapters added with the deltas for the Plus2:

Robinshaw, P. and Ross, C. 1995. Authentic Lotus Elan and Plus 2. Motor Racing Publications LTD. ISBN 0 947981 950.

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PostPost by: LotusNWT » Sun Jul 05, 2009 8:48 pm

Hi

Thanks to everyone for the very helpful information. Sure enough it is right on the TAC positive earth. So I suppose the best place to start is checking the conections and I think I may try running a line direct to the gauges as was suggested

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