Positive or negative earth?

C

cas

New Member
Hello, does anyone know if there is a way to distinguish between negative and positive earth cars? I have read several things from "if it has a rev-counter, it is negative earth" and the workshop manual tells me that a car with B in the chassis number should be a positive earth car. Now my car is a 1966 series 1 2000, single carb, LHD, with a rev-counter, chassis number: 40304860B so it should be a positive. I bought the car with no battery, and watched the previous owner try to start it with a negative earth set-up (it does run with ether). I am fairly certain the petrol pump is bad, but since I understand that you can ruin one by hooking up the battery wrong, I don't want to order one and ruin it immediately. I know you can switch to a negative earth, but how can I tell how this car is set up? Are there any differences that are visible? Thanks in advance, Christian

If it helps: when the battery was connected (negative earth) the windscreen wipers did function as they were supposed to...
 
I guess the ignition coil is still wired, and it should have + and - signs on its teminals.
So you can use that one as a reference. See what terminal (+ or -) of the coil is wired with live, from the ignition switch. If it's the positive terminal, then the car is negative earth.
Also, the tacho should write somewhere on it's face positive or negative earth. Take a look at the back of it, and if everything seems OK (no reversed earths with lives) then the car should be wired as per what it says on the tacho.
Last but not least, does the car have an alternator or a generator (dynamo)? If it has an alternator fitted, especially the later Lucas ACR series, then it should be definately negative earth. If it has a generator fitted, it could be either positive or negative earth, if you cannot tell from anything else, but in this case it is time for you to decide to have a negative earth car! So, polarise the fields in the generator accordingly (you' ll find the procedure somewhere, it's very easy), take a look at the clock and tacho connections to be wired accordingly, connect the coil in the right way, finally the batery and off you go!
I hope that this helps,


Demetris
 
Thanks Demetris, That will be a big help. The face of my tach has no polarity marks but the coil is still hooked up so that will be the place for me to look. I just picked the car up and have not become very familiar with it, but I do believe it is a generator (much longer than any alternator i've seen?) This car has really humbled me, everything I have taken for granted working on american cars has been called into question... So I end up asking stupid questions like "how do I hook up my battery" haha thanks again, I will check it out in the morning.
 
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