15 replies to this topic

[Gcal]

OK folks I'm new to the forum and need a bit of help. I have a 1978 mini 850 and unsure whether it is positive or negative earth, Haynes have it listed from 1969 onwards as negative earth if anyone has a mini of a similar age that could help.

[RedRuby]

It should be negative earth, presuming you have a battery fitted the shorter connector, usually black coloured, is nearest the boot lid and connects to the terminal marked "-" on the battery, your battery clamp may also be marked "-". The battery cable further in that disappears through the boot floor may be coloured red, have a "+" mark on the battery clamp or a red plastic cover. Of course it all depends on whether anyone has changed cables or clamps and not done them correctly.

[slidehammer]

Should be negative earth at that year.

[Gcal]

I thought it was negative earth, would it cause any damage if the battery was connected wrong?

[Carlos W]

I thought it was negative earth, would it cause any damage if the battery was connected wrong?

Possibly. 

 

There are all sorts of diodes in the alternator that probably wont like it

[billy big skid]

I thought it was negative earth, would it cause any damage if the battery was connected wrong?

A bang, many sparks and a large lump on the back of your head from when you leapt backwards and rattled it on the parcel shelf.

[CityEPete]

Getting the magic smoke back in can take ages!

[panky]

If you've got a stereo fitted then it's probably fried

[Twincam]

Converting to negative earth is fairly simple - how-to guides can be found on the net.

Where are the connections on the coil hooked up to? You'll have to swap these over when converting (and other bits too)...

[Gcal]

Negative on coil to dizzy and positive on coil to solenoid

[tiger99]

If you have an alternator and have reversed the battery, the alternator will be ruined. It is unlikely to work at all, but if it does it will be for a very short and unpredictable time. The diodes and windings will have been grossly overheated.

[Gcal]

Been out and checked connections and it turns out that it is positive earth after all with an alternator,if I swap the battery terminals the ignition light stays on,how easy is it to convert it?

[Swift_General]

What makes you think it's positive earth? Not sure when the changeover was (I'm thinking possibly '69 with the Mk3?) but certainly long before '78. Also never heard of a positive earth alternator.

[Carlos W]

Been out and checked connections and it turns out that it is positive earth after all with an alternator,if I swap the battery terminals the ignition light stays on,how easy is it to convert it?

 

Please don't swap the battery connections around

[Gcal]

Red positive terminal cover on earth wire and battery cable has smaller connection and earth has the larger battery terminal