Thread: 2A 2.25 Military polarity.

68 should be negative earth (change was 67), but if fitted with a generator, (as originally supplied) nothing will be damaged if incorrect polarity is used. If it has been converted to alternator, it will certainly be negative earth and the alternator and sundry wiring is likely to be fried if connected backwards.

John

Originally Posted by JDNSW

68 should be negative earth (change was 67), but if fitted with a generator, (as originally supplied) nothing will be damaged if incorrect polarity is used. If it has been converted to alternator, it will certainly be negative earth and the alternator and sundry wiring is likely to be fried if connected backwards.

John

Thanks John,
It has a Bosch 9 120 060 600 U-K1>14v 35A 20 alternator in it so I'll go with negative earth and see how it goes. Should tick over, motor winds with hand crank and compression seems ok. I'm sure you'll read more.
Ta,
Dave.

G'day Kodez23

The 67-onwards (keystart ignition) were all negative earth, that is when Lucas Ltd changed all their electric systems, so there will be no problems,all earlier series Landrovers with push solenoid start were POS earth originally, but may were converted, my 2a GS is a 68 model 4/68 ARN 272-484 has you alternator got an internal regulator?? (little black box on the back) if so, you can easily update with a higher amperage unit quite easily,to a 50/55 amp unit from a Datsun from memory,my old 40 amp unit has Dato internals in the old case, and is now 55amp, alows me to run driving lights if needed.



cheers

Hi all

I am a little confused with the 1967 onwards that Army Land Rovers were negative earth. the question is, if someone could help me here.
I have a 1970 FFT with a generator, not an alternator.
Going by the electrical drawings on the REMLR. wiring diagram for Land Rover-Army-12V-FFT Drawing No. 1101-3-005, Dated 1/7/68. the Battery is connected, Positive Earth. so I assume a 1970 FFT is connected Positive Earth. Is this correct.

Regards
Mike

1970 generator equipped came from the factory negative earth. I would guess, that although the document is dated 1968, it is correct for Landrovers up to 1967 - although it is quite possible that in July 1968 Landrovers actually built before the polarity change were still being delivered!

It may be worth noting the reasons for change. Prior to the 1930s, polarity was usually negative earth, this providing a slight reduction in corrosion of terminals. However, with the changeover to coil ignition rather than magneto ignition, it was found that better spark plug operation was obtained using positive earth, as for an "autotransformer wound" coil, this made the centre electrode negative, giving best spark performance. It probably never was a very significant advantage, however.

By the 1960s, another factor came into play. The introduction of transistors in 1948 led to the development of much improved car audio equipment, and by the 1960s it was obvious that increasingly transistor equipment was going to be fitted to or used in cars. Early transistors were PNP germanium types, and most circuits using them demanded negative earth. Although much equipment was made in the early days of transistors that could be switched to either polarity, this complicated design and invited expensive errors. As a result, there was a general move in the sixties to negative earth systems. As indicated above, Landrover made the change in 1967, probably pretty much dictated by their electrical supplier, Lucas. They would have been concerned to standardise on one polarity as alternators replaced generators; unlike the latter, alternators cannot be easily used with either polarity.

John

Thank you gentlemen..Unc H and JD as usual you are a wealth of information

Mrs hh

Thanks John for the detailed information and clearing up my confusion.

Regards
Mike

G'day Folks

All 2a vehicles from suffix "D" chassis onwardsand all Series 3's were manufactured as Neg Earth with Lucas C39 or C40 generators as standard equiment, the Lucas Alternator did not appear until the Series 3.

BUT,all military Ambulances were fitted with an "Email" brand alternator as standard,Neg earth from 62 onwards,these were sourced from the then current Chrysler Valiant range,external regulator type.



cheers