33 replies to this topic

[Mk1Ruby]

How big a job is it to convert a mk1 mini to negative earth so I can run an alternator

[mattbeddow]

Ive not done it myself but i imagine its a rather large job. Everything will need to be rewired.
if there is a kit out there then that will make things easier but if not then its gonna be a big job

[pdaykin]

Very easy job to convert from positive to negative.

• Disconnected battery. Turn the battery 180 degrees and place back into the tray so that it now sits in the opposite direction
• Attach the battery cable leading to the starter solenoid to the positive terminal of the battery.
• Do not connect the ground connector to the negative terminal of the battery
• Switched the low voltage leads on the coil. If required, disconnected leads, loosen the coil clamp and rotate the coil 180 degrees before reconnecting the wires to preserve the lead routing.
• Disconnected the smaller wire (brown/green) on the dynamo, labelled “F” or field.
• Connect the ground connector to the negative terminal of the battery
• Re-polarise the dynamo by connecting a short insulated wire (later referred to as a jumper wire) to the large brown terminal connection on the starter solenoid, making sure that you have good metal-to-metal contact. Lightly touch the other end of the jumper wire to the field (F) terminal of the dynamo a couple of times. This is likely to produce a spark. Removed the wire from the battery.
• Why re-polarise? If you not, you will be losing significant voltage at the spark plugs. The vehicle may still run, but it will run poorly.
• Reconnect the wire brown/green wire previously disconnected from the field (F) terminal of the dynamo

[Yoda]

Beat me to it! but as you can see, NO need to rewire everything.

[Mk1Ruby]

Cheers for the help people :)

[surfblue63]

When I converted my Mk2 Traveller from a +ve earth dynamoe to a -ve earth alternator I followed this method as found on the Mini Spares web site. It is quite simple to do and does not involve rewiring the whole car!

http://www.minispare...a8-64fccf15512e

Completing this change successfully, easily and neatly is pretty straightforward on a Mini. The alternator contains the regulator and cut out functions within it’s casing, so makes the regulator box used with a dynamo redundant.
Part No Applications: GEU205, GEU205MS, GEU207, GXE2297
However, it is useful to retain the box itself and it’s connectors. It acts as a terminal box to make the installation neat, avoiding the messy and awkward soldering/taping together bunches of wires. It also maintains a period look, plus makes reversal easy should this be needed in the future.
Disconnect the battery and remove the black regulator box from the car - taking care to make a note of or label each wire removed with it’s original terminal connection. Fit the alternator using the necessary rear support bracket (part no. 12G1053) as the alternator is shorter than the dynamo. The relevant belt (GCB10825) is also needed. The alternator has a smaller diameter pulley to drive it at a higher speed than a dynamo, giving better output and therefore battery charging at lower engine speeds.
Take the regulator box cover off and dismantle it. Remove all of the coils, contacts and connections to the blade terminals on the bottom of the unit, but retain the blade terminals. Double check that all connections to the terminals are removed, then using some heavy cable - 2.5mm or larger - solder links between terminals A, A1, and D, connecting all three together. Now solder a link between terminal F and E. Replace the box in the car and re-connect all the wires to their relevant terminals except the ignition warning light wire (brown/yellow) which must now be connected to terminal E. Connect the ex-dynamo wires to the alternator - large connector to the large terminal (output connection) and the small one to the small terminal next to it (sensing terminal).
If the car being converted was already negative earth, re-connect the battery and away you go! If the car was positive earth, you will need to reverse the connections to the battery and swap the connections on the ignition coil.
If there is a radio or cassette player fitted, check to see if these can be re-connected as negative earth. If not, then unfortunately they will need replacing. Everything else should work as normal.

Here's a pic of my Mk2 engine with the alternator in place

Edited by surfblue63, 16 July 2012 - 08:42 PM.

[mattbeddow]

Hmm, ok, i was 99% sure that anything electronic like fans in heaters and radios would need to be reversed to still work correctly. Obv bulbs will still work regardless.
Suppose there isnt that much in a mk1 tho

[dklawson]

There are no issues with motors requiring re-polarization or wiring reversed. The biggest challenges are if you have installed positive earth accessories in the distant past (radios, tachometers, etc). Otherwise the swap is exactly as described above and there is no re-wiring except for reversing the coil connections and the battery connections.

However, to clarify what PDaykin said...
8. Why re-polarise? If you not, you will be losing significant voltage at the spark plugs. The vehicle may still run, but it will run poorly.
Rewiring the coil is not the same as re-polarizing the dynamo. If you fail to swap the coil leads, you will have less spark energy as stated and the engine may run poorly. Re-polarizing is a term reserved for changing the residual magnetic field in the dynamo. Failure to "flash" re-polarize the dynamo when you switch the battery connections will result in white smoke coming out of places you do not want to see white smoke.

[mattbeddow]

Electric motors would defiantly need rewiring else theyd spin the wrong way!

[dklawson]

That all depends on whether they are permanent magnet or have wound field coils. For example, you do not have to change the wiring of wiper motors.

There are many online guides for things to do when changing a Lucas wired car's polarity. None I have seen discuss or mention rewiring any of the motors.

[mattbeddow]

The motors still spin the other way
Its the mechanism itself that makes the wipers work regardless of which way the motors spin.
The only one i can think you would need to change would be the heater fan if fitted

[surfblue63]

The motors still spin the other way
Its the mechanism itself that makes the wipers work regardless of which way the motors spin.
The only one i can think you would need to change would be the heater fan if fitted

They didn't spin the wrong what when I did mine, but I guess you know more about car electrics than Kieth Calver, who wrote the article I quoted!

You do not need to rewire any parts of the electrica system other than those mentioned in the article.

Edited by surfblue63, 18 July 2012 - 09:02 PM.

[dklawson]

The motors still spin the other way

Not so. If the motor has wound field coils (not permanent magnets) it will spin the same direction as before because the current is flowing the opposite direction through the field coils when you switch the (+) and (-) wires. The biggest example of this is not the wiper motor or the fan motor... it is the starter motor. Your engine is not going to turn backwards when you change the car's polarity.

[mattbeddow]

Ok, ill yield on the wound field one now i know what you mean by wound field motors, (i was previously thinking you ment brush-less motors where the windings are in the stator not the rotor) but I know how arguments on forums get after a few posts so im just going to leave this here because you obviously think i dont have a clue. i mean its not like i have an engineering degree or anything that teaches you all about electricity and such... oh wait... i do


to be honest, if i was that bothered id draw lots of pretty pictures that showed how the wiper mechanism works regardless of which way you spin the motor but im not so i wont.

[dklawson]

I never suggested you didn't know anything and for the record, I am also an engineer. Sorry if my terminology was unclear regarding motors with wound fields as opposed to permanent magnets.