positive or negative?

Post by **mrpleasant** » Sun Apr 18, 2004 6:39 pm

hi all,from memory and workshop manual i presumed moggies have
positive earth.however after my battery died today i discovered said
powerpack was installed(not by me) with a negative earth.
3 questions,if u can help please.
1,is this normal practice?
2,if not,are there any problems/advantages/disadvantages with this?
i have.
i have temp battery now fitted and have followed manual and made positive terminal earth,seems to run ok but am wondering if some sort of conversion has been made in the past and if i should revert to negative earth,any ideas?
thanx in advance.
stay pleasant, mrp

Post by **salty_monk** » Sun Apr 18, 2004 6:56 pm

It's normal practice. Read the page in the technical tips section for more info. You have to re-polarize the coil to run negative earth so I think unless you have done this to re-polarize it for positive you may have problems.

Best bet is to go through the whole process as detailed properly.

The only thing you will find that runs any different on negative earth is the heater fan which may run backwards & not be anywhere near as efficient unless the polarity is switched on the connections (if this has already been done yours will now be running backwards as you have reversed the polarity....)
The main reasons people convert over is to either run a radio or to run an alternator as opposed to the standard dynamo. I hope you have neither as if you have you will have successfully have fried them!!

Post by **mrpleasant** » Sun Apr 18, 2004 8:35 pm

many thanx salty,
will revert back to the negative earth.
fortunately i have no alternator and took the precaution of
disconnecting the radio.
stay pleasant,mrp

Post by **Willie** » Mon Apr 19, 2004 7:55 am

ALSO if you have reverted to POSITIVE earth then check that
the coil contacts are correct i.e. if the coil is marked SW and CB
the CB lead should go to the side of the distributor. If the coil
is marked + and - then the + lead should go to the dizzy.
It will still work the other way but loses some efficiency.

Post by **rayofleamington** » Mon Apr 19, 2004 11:31 am

The coil runs more efficiently with the current flow in the correct direction, but the dynamo also has to be polarised. After you've swapped around a couple of times be careful to make sure the dynamo is still working.
It's hard to break them but it is possible to confuse them. I guess the article in tips section describes what to do to change the polarity of the dynamo (if it does give you trouble). If it charges ok, then don't worry.
Good luck

Post by **uclarge** » Tue May 11, 2004 12:00 pm

I personally believe its a good idea for the conversion, especially if you are wanting to install some sort of music system? like a modern cd player or something similar? I personally did my conversion myself, i got the "how to do it" from this site! it only took me about 20mins, and my moggie (Boris) has been running fine! and ive got a cd player in!, makes journeys alot more fun. go 4 a conversion!
charly

Post by **salty_monk** » Tue May 11, 2004 1:19 pm

Charly.... read all the thread before posting otherwise you just end up looking silly or making no sense or both... We've all done it I'm sure..