Lotus Elan

polarity. what has been done?

PostPost by: john.houston » Fri May 28, 2010 1:10 pm

Hi While I am here could I ask a more detailed Question.
When I bought my car 69 +2 the P.O said He had changed polarity so he could fit an alternator ,this also stopped the Tacho working. That was it, not much more than that I thought nothing of it , but 3 yrs later and a total strip down I would like to know a bit more. Basically what has been done in the change ?
The battery had gone so no clues there. When I fitted the starter back i wondered if this is unafected by the change over- must be it started the car for him!! . Do I connect the black cable to the black terminal on the new battery ? Also can the tacho be fixed?

Thanks again John.
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PostPost by: bob_rich » Fri May 28, 2010 2:42 pm

Hi John

The starter and all other motors should not be effected by the change of polarity of the battery. from what you said you now have an alternator, fitted by the previous owner and that was fitted 3 years ago and should be OK. I assume the car has run with the polarity swop that was done. The tacho may be fixable it depends what type it is. There should be a number on the front dial some where along the lines RV1 2234 *** for example. with the number known it will be possible to see if it is a reversable polarity type in which case changing the supply leads over and perhaps changing the direction of the current pick up that triggers it it may be OK. Should be info on this on the web. possible running for a long period with supply back to front may have damaged it but it could also survive

hope this helps

best of luck

Bob
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PostPost by: rdssdi » Sun May 30, 2010 11:26 pm

It appears that the +2 was converted to negative earth at unit 1087. Earlier for U.S. bound cars.

What number is your car? I thought Lotus had changed to negative earth by 1969 MY.

I am restoring a 1963 Jaguar MK2 which is positive earth. I have yet to decide whether or not to change.

My 1969 +2 (2060)U.S. version and my 1968 TVR Vixen were factory negative earth.

Bob
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PostPost by: john.houston » Mon May 31, 2010 12:05 pm

Hi Bob .
My car is Jan 69 one of the last +2s with the "thin" seats so I think it was a possitive earth one and also the P.O said he paid a large ammout for the alternator bracket when he converted it.The thick battery feed wire to the solenoid is black as is the starter wire.
Really I would like someone to give a rough guide to what has been done in the conversion and would greatly appreciate how the new battery will be wired +to + or
+ to - . Thanks again John.
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PostPost by: nebogipfel » Mon May 31, 2010 2:43 pm

John,

Typically changing from positive to negative earth is simply a matter of repolarising the dynamo (not needed when an alternator is to be fitted), reversing the connections on the ignition coil and swapping the battery around. On some cars (Lotus included) the tacho will need changing or converting and some old radios were positive earth only.

This is a common mod' and no great drama is involved. If you intend to stay negative earth then simply make sure that your new battery -ve terminal is connected to chassis earth and the +ve terminal is connected to the starter solenoid.

Such things as starter motors are unaffected by polarity change. :wink:
John

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PostPost by: john.p.clegg » Mon May 31, 2010 4:15 pm

John

One clue,the battery connections are different sizes..are they still there?

John :wink:

P.S. The starter motor is unaffected and you can/should change your Tacho for the required type "neg earth"
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PostPost by: bob_rich » Mon May 31, 2010 7:05 pm

Hi John.

If I had a bit more info on the tacho type it may be possible to see if it can be reversed in polarity by external connections. A number of them were. Regarding the battery positive or negative earth means that the battery positive goes to the car chassis ( usually on older cars) terminal marked +on modern cars -- most after the mid 1960 when alternators came in then the negative terminal goes to the car chassis. Colour did not mean much as most battery leads tended to be black whether +ve or - terminals used. As the other post stated if there is a radio fitted this need to have the correct earth as well. Generally if you have an alternator fitted and disconnect the tacho then all should work fine when you connect the battery -ve terminal to the car chassis.

Hope this helps best of luck

Bob
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PostPost by: john.houston » Mon May 31, 2010 9:03 pm

Thanks to the 3 members for their answers I can now carry on. The PO fitted a modern radio so I will keep that in if an old one crops up I will see if that can go in. . Its a lot easier to work on the engine when its sat in the chassis. After 3 years hard work to misquote Robert Duval I dont love the smell of burning plastic in the morning.
I would love to get the Tacho working so when I get to that box I will ask your advice and I will list more details.
Many thanks John.
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