Converting to Negative Earth

Post by **MrA.Series** » Wed Dec 03, 2003 1:33 pm

Can anyone tell me all the pros' and cons' of changing over to negative earth? And how I go about doing so if I wanted to (not made up my mind yet...)

Cheers,

Rob

Post by **Kevin** » Wed Dec 03, 2003 1:36 pm

The easiest way Rob is to read section 16 of the technical tips its all in there

Post by **MrA.Series** » Wed Dec 03, 2003 1:38 pm

Thanks!

Post by **Willie** » Wed Dec 03, 2003 8:15 pm

The Pros....you can then fit a modern radio/CD, and an
Alternator if you wish. Cons? when you turn the battery
round as part of the mod then the retaining bar for the
battery is quite close to the contacts...solution, cut away
some of the metal opposite the terminals.

Post by **salty_monk** » Thu Dec 04, 2003 3:16 pm

Do you run the risk of the fuel pump contact giving up the ghost? I read this in Practical classics?? Also the distributor contacts if they're near the end of their life anyway...

If so I guess best to have a spare set when you do it.

Does it effect anything else?

Post by **Willie** » Thu Dec 04, 2003 5:17 pm

Yes, for maximum efficiency you should swop the two thin
leads on the coil over. I personally never had any trouble
from the fuel pump or the distributor points.

Post by **iwant1** » Mon Feb 16, 2004 10:34 pm

How can you tell if the car is already negative earth. I have the negative terminal connÍcted to the braided non-insulated wire and all is okay thus far, but i dont know the history of the car and therefore dont know if it has been converted. Its a 1968. If it is positive earth, would it still run with the battery in the wrong way?

Post by **Cam** » Mon Feb 16, 2004 10:52 pm

I have the negative terminal connected to the braided non-insulated wire

That wire should be bolted to the body, if so, then you are negative earth (like the modern cars) and can run modern stereo equipment.

The car will run with the battery the other way around IF you re-polarise the dynamo (5 min job) and swap the coil leads over. But it sounds like you don't need to as you are already set up!

I would imagine a lot of Minors (certainly later ones) have already been converted.

Post by **shymoggie** » Tue Feb 17, 2004 6:16 pm

This might be a silly question but:

If you reverse the polarity of the car's power supply (battery) won't all the electric motors.... fan blower, starter motor, spin backwards ?

Post by **Cam** » Tue Feb 17, 2004 6:29 pm

Nope!!

Actually some do but it does not matter, for example the late heater does spin backwards but it's a barrel type design so it still pushes air out, it's just that it's not as efficient.

Post by **salty_monk** » Wed Feb 18, 2004 4:08 pm

it's just that it's not as efficient

Hummmm, no change there then... 100% less efficient than zero is still zero...

Post by **rayofleamington** » Wed Feb 18, 2004 4:13 pm

Does it effect anything else?

I heard that positive earth can accelerate body corrosion, but I was never sure how much difference it makes.
Certainly you can now buy anti corrosion kits which put a charge to the bodywork (although not seen any independant test results...) so maybe there is some logic to the theory.

Post by **Cam** » Wed Feb 18, 2004 4:46 pm

Well after 30, 40 or 50 years of the Minors being positive earth I don't think it's that critical

Certainly not something I would loose sleep over!!

Post by **iwant1** » Wed Feb 18, 2004 9:04 pm

Cam, just to check for sure, which way around should the wires be on the coil i'm probably being paranoid but hey.

Post by **Cam** » Wed Feb 18, 2004 9:13 pm

Well, if it works then there's a good chance that it's the correct way round so don't change anything, but anyway:

For a NEGATIVE earth car with a POSITIVE earth coil (original type), it should have the white wire connected to the CB terminal and the white wire with a black tracer on it connected to the SW terminal. This is the opposite way around to normal (positive earth).

Post by **iwant1** » Wed Feb 18, 2004 9:25 pm

Okay cheers cam dont suppose you know anything about door repairs? also i think my coil wires are yellow!

Post by **Cam** » Wed Feb 18, 2004 9:31 pm

The coil wires are supposed to be white, but after 30 odd years of muck and heat I suppose a bit of yellowing is to be expected!

If you want to repair your door bottom (due to rust) then it's not too bad if you can weld as the repair panels are readily available to replace the door bottoms. If you can't weld then it's probably better to try and locate a 2nd hand door and just swap it over!

Post by **Willie** » Mon Feb 23, 2004 8:02 pm

Having just upgraded to a late type heater on a Negative
earth car I can state that if your car has been converted
WITHOUT the heater leads(outside,down the left hand side)
being swopped over the air output of the heater fan is
VERY much less than it should be.

Post by **57traveller** » Wed Feb 25, 2004 10:09 am

Willie - to save me lying on my side and upside down, are the heater motor supply wires accessible with the heater insitu? My '57 Traveller is also fitted with the later heater and never having one when built is on permanent recirc. It is -ve earth and I suspect the supply is possibly connected wrong way round and fan speed/air output could be better. I only have my '62 saloon to compare this with, it has the 2nd type variable speed and fresh air facility, the air seems to blast out of that, more so than the Traveller.

Post by **Willie** » Wed Feb 25, 2004 2:35 pm

YES, if you look down the left hand side of the heater you will see,
at the rear the 'bulge' of the end of the heater motor. There are
two leads to this motor(Lucar push on connectors) diametrically
opposite. If you wish to check for maximum fan power then
swop these two leads over(on my car I had to lengthen one
lead,you may be luckier) the difference is considerable.

Morris Minor Owners Club

Converting to Negative Earth

Converting to Negative Earth

Neg earth

converting

polarity

heater