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Bob Claffie

Bob Claffie

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My new to me 100/6 is finally coming home to roost Tuesday. First question is: How do I tell if it is a Pos or Neg system. The P.O. alluded to a possible change over years ago but since it doesn't have a battey or fuel pump, where do I start and how can I tell which it is? If I do connect it backwards what is the most damage I can incur? Thanks, Bob
 
HI Bob, do not hook it up until you are sure of the ground configuration.Here is a thought, take a good look at the wiring on the coil,if it is as original{Positive GND}the terminal on the coil marked "CB" wil be routed to the distributor lucar terminal.If the coil has been replaced with a more modern unit then the terminal marked " + " will be routed there.If the car has been converted to{NEG GND} then an original coil will have the terminal marked "SW" routed to the distributor or if a more modern coil is in place the terminal marked { - } will be routed there.---Fwiw---Keoke
 
Hello Bob,

the usual polarity sensitive components are some S.U. fuel pumps (but as you don't have one that is irrelevant), tachometer and accessories like a radio. I presume that it still has a dynamo rather than an alternator, so if that is connected reverse to it's last configuration it probably won't charge.
If your tachometer, which normally is marked as to it's polarity, has been reversed internally then you could blow some components in that.

Alec
 
[ QUOTE ]
My new to me 100/6 is finally coming home to roost Tuesday. First question is: How do I tell if it is a Pos or Neg system. The P.O. alluded to a possible change over years ago but since it doesn't have a battey or fuel pump, where do I start and how can I tell which it is? If I do connect it backwards what is the most damage I can incur? Thanks, Bob

[/ QUOTE ]

Disconnect the dynamo, connect it's field and output together, connect a voltmeter between these connections and its frame.

By hand (fanbelt off) spin the dynamo in the direction it would nomally turn. If the o/p volts are +ve then its -ve earth and vice versa.

Quod Erat Demonstrandum !

You may also get good clues examining the heavy bettery leads.

AWEM
 
Since your new acquisition doesn't have a fuel pump you're faced with your first decisions about originality vs. reliability/compatibility. You can follow Keoke's notes and connect the coil up for negative ground and install a negative ground fuel pump. For safety, repolarize the generator for negative ground, and install your new battery that way. This will allow you a lot of "modern" options (like radios) for your car that would otherwise be more difficult.
 
i would think the easiest way to find out would be to check the heavy battery terminals (+or- to ground)but i also have a guestion about this matter,can someone please explain what is probably obvious to others,what the heck are the advantages of switching over?is it because so many people are accustomed to working on neg. grounded autos?are the circuts or elect. components protected any better?is it because some owners want to change from a 'dynamo' to an altenator?the last time i checked it hadnt even been determained in what direction electrons travel!keoke,whip me if you must,but i just dont get it!i dont know maybe 'lucas'components should have been designed the other way around!thanks in advance,anthony7777 1963 bj7 M.K.II /ubbthreads/images/graemlins/confused.gif
 
NO, 7777 it simply adds the convience to upgrade the cars electrics to the most readily available electrical components. Stick with current flow and you won't be so befuddeled---Keoke /ubbthreads/images/graemlins/laugh.gif
 
The battery cables may help.
One of the battery terminals is larger than the other, so your cables may give you a clue; one will have a larger opening than the other.
 
"the last time i checked it hadnt even been determained in what direction electrons travel!"
I thought everyone knew that electrons flow from neg to positive and consequently the electrical " force " travels from positve to negative. /ubbthreads/images/graemlins/shocked.gif
 
Upon close inspection I determined that the wire from the neg term on the coil goes to the side of the distributor. Would that make the system Neg ground? Since there is a mechanical tach , that will not be a problem. How do I change or check the polarity of the generator? I am going with a solid state elec pump. Originality is nice but I am leaning toward making a good looking driver. If after the "restoration" the car drives well enough I may rethink that and go for a more correct car. Thanks, Bob
 
HI Bob, Yes if the "Neg" terminal on the coil goes to the Lucar terminal on the distributor it suggests that the car is Negative ground. Polarising the generator only requires that the field wire on the generator be disconnected and the unterminated field terminal on the generator be momentarily struck to the ungrounded terminal of the battery---Keoke
 
[ QUOTE ]

HI Bob, Yes if the "Neg" terminal on the coil goes to the Lucar terminal on the distributor it suggests that the car is Negative ground. ---Keoke

[/ QUOTE ]
Note the "suggests" part. It's possible that a previous owner connected the coil backward. The checking battery cable terminal size mentioned above would give a pretty good idea of how things were previously connected.
D
 
Yep Dave, but if the PO put some of those drug store type bolt on battery connectors in you just might still be on square one.---Keoke

Actually Dave,he can proceed using the negative ground concept,I had to go back and make sure he was not intending to install a Pertronics at this time too.All that is left is to polarize the generator and he is all set for other negative ground up grades if he chooses.Even the pertronics installation is somewhat simplified using the NEG ground system.
 
[ QUOTE ]
>>SNIP<< How do I change or check the polarity of the generator? >>SNIP<< Thanks, Bob

[/ QUOTE ]

Bob,

My previous post tells you how to check the generator!!!!!!

If you need to change it, the polarity depends on the residual magnetism of the ironwork. With the frame connected to ground flash the field coil terminal to battery +ve for a neg earth car, and to battery -ve for a pos earth car. This switches the magnetic domains to the way you want them.

AWEM
 
Bob, I guess what we are all saying is rather than trying to figure out which way it " was" , just make it the way you want it. It is just as easy to make it the way you want as it is to figure out which way it used to be. Simply hook up the desired battery polarity to ground and flash the oposite polarity of the battery to the field of the generator as Andrew has outlined. Your coil wires are already correct for neg ground so if that is what you want, just connect the neg. battery post to the frame ground and flash the field with a wire from the positive post. /ubbthreads/images/graemlins/cheers.gif
 
Thanks, all. Andrew, I didn't completely understand what you were telling me in the first post, now is all clarified. Unfortunately, the car does have those cheesy aftermarket terminals on both cables ie: same size, so no clue there. Once I have changed or confirmed that it is now Neg grd is there anything else that needs attention? I already have a spare "FACET" neg grd pump to go in , how about the starter connections, etc ? Thanks again, Bob
 
Well Bob, Ifin was me I would take that Facet pump right back where I got it and get me a Negative Ground Electronic SU fuel pump.But then again it ain't me. The starter and the rest of the electrics in the car could care less which ground system you choose to use, except the radio if one was included.---Keoke
 
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