positive or negative

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Lazy Landy

Lazy Landy

New Member
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Durham
been looking at the doozel lump that i just droped in my motor and the wiring is a bit odd, the No. 1 heater pulg has a wire comming from No. 2 and a wire going to earth on the timing case, all i know is the it was out of a 2A.​
 
The GOLDEN RULE

Dynamos in UK were invariably POSITIVE earth systems

Alternators are almost invariably NEGATIVE earth systems.

However, glow plugs don't care about polarity. They just need to be wired correctly, and if your Landy ever was a 2.25 diesel you could be heading for a wiring mess, as those engines connected glow plugs in SERIES, and through a ballast resistor.

If you fit a later diesel, chances are its plugs should be connected in parallel, and NOT though the ballast resistor.

CharlesY
 
CharlesY said:
The GOLDEN RULE

Dynamos in UK were invariably POSITIVE earth systems

Alternators are almost invariably NEGATIVE earth systems.

However, glow plugs don't care about polarity. They just need to be wired correctly, and if your Landy ever was a 2.25 diesel you could be heading for a wiring mess, as those engines connected glow plugs in SERIES, and through a ballast resistor.

If you fit a later diesel, chances are its plugs should be connected in parallel, and NOT though the ballast resistor.

CharlesY
Click to expand...
you do get neg earth dynamos but you don't get pos earth alts! so yer golden rule is more of a murky brown colour
 
slob said:
you do get neg earth dynamos but you don't get pos earth alts! so yer golden rule is more of a murky brown colour
Click to expand...

Not quite true on both counts.

ALL dynamos can easily be made to run either POSITIVE or NEGATIVE earth.
It is only a question of knowing how to "flash" them to get the polarity set to start with, or even later to change it. Once the residual magnetism in a dynamo is set up, it will self-excite only the right way.

Nothing much will go wrong anyway. The starter motor will NOT run backwards because it is .... well, it just won't - so there. Nor will fan-blowers and radiator fans either, so long as they are series-wound which is probable.

There ARE positive earth alternators to be had, for use when polarity matters but you want to dump the dynamo for an alternator. But they are rare.

Easy-Peasy to have a dynamo arranged for either system, but POSITIVE earth is almost always the rule, especially in UK. If anyone wants to argue, they can let me know of a UK make and model in the last 50 years that uses a negative earth dynamo system. I'm waiting ....

CharlesY
 
njust to save you a long wait ...triumph spitfires and vw beetles both had neg earth dynamos fitted at some time... probelly some other triumph models as well..and we know how easy it is to swap them from neg to pos. specially today wiff al the info available on the net.


oh we know VW int a brit make but am sure the likes of morris and austin had them aswell. just not so sure on them ..

can you supply a make that uses a pos earth alt??
 
CharlesY said:
ALL dynamos can easily be made to run either POSITIVE or NEGATIVE earth.
It is only a question of knowing how to "flash" them to get the polarity set to start with, or even later to change it. Once the residual magnetism in a dynamo is set up, it will self-excite only the right way.

CharlesY
Click to expand...

I "self-excite" myself quiet often and I dont need to be flashed for it to happen
 
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