changing to negative earth

[aupickup]

well i know how to do it
but do i have to change over any wiring to fuel pump, heater, wiper motor etc

[Trickydicky]

Here is the clubs write uo about it.

http://www.mmoc.org.uk/index.php?page=322

[IslipMinor]

As above, the wiper runs in reverse, but it has been doing it in ours for ~40 years and was still going strong until yesterday, when I replaced it with a 2-spd version.

You may need to make a small adjustment to the park position, as now it will come into the insulated sector, under the cover marked with the red arrow, from the opposite direction. Normally you only need to undo the 2 screws on the left hand end of the cover to allow the park cover to rotate slightly.
[frame][/frame]

[aupickup]

TA GUYS

[bmcecosse]

The Minor wiper motor DOES NOT run in reverse! When the polarity is reversed, both the field and armature currents are reversed and so the direction remains the same......... To reverse a motor you change only ONE of the two current flows. There have been suggestions that the heater motor runs backwards - this may well be so - IF it is a permanent magnet motor, which it may be - I have never stripped one down. My own motor is ex late Mini and was designed for -ve earth in the first place. The fuel pump contacts should be cleaned, and the coil connections reversed.

[Declan_Burns]

The heater Motor does run the opposite way to the arrow on the rotor regardless of the polarity.
Regards
Declan

[bmcecosse]

Regardless of the polarity????

[Declan_Burns]

I mean whether the car is positive or negative earth the heater motor turns in the opposite direction to the arrow on the rotor. I have bench tested it several times.
Regards
Declan[frame][/frame]

[IslipMinor]

the wiper runs in reverse

No, it does not! That's a myth well and truly busted! Like a number of, maybe many other people, I had accepted the very common wisdom the wiper motor rotation direction was a function of polarity. Since both armature and field are wound I should have known better, so have just tested our old original 1958 wiper motor connected to the battery charger and sure enough it goes round in the same direction, irrespective of connection polarity. Interestingly it 'sounds' slightly different, one polarity is quieter than the other, but the direction is constant!

The things you learn on this forum.

P.S. Tech Tips needs to be updated!

[bmcecosse]

The later 'round can' wiper motors from Minis (and TR7s !) etc may well be permanent magnet motors (I don't know - have never had to strip one) - and are designed for negative earth running (since that was the 'rule' when they were introduced) - it's entirely possible they would (try to) run backwards if connected +ve earth. I don't recommend it - would maybe smash the parking switch. Your heater motor is interesting Declan! Must therefore be a field + armature motor - but it's strange it always appears to run 'wrong direction'. I wonder if at some point the field connections have been reversed internally in a mistaken belief this would be necessary when the car's polarity was reversed.
Mind you - some years ago I installed a new cooling tower (size of a typical living room..) at work (large fans very much like your heater fan Declan), electrician wired it all up to rotate as per the arrows on the casings.......when the equipment came on line after the shutdown it wouldn't cool worth a damn...... The arrows were wrong! Reversed the motors and all well...... The manufacturers refused to accept the arrows were wrong - and refused to pay for the emergency electrical call out to reverse the motors.

[Declan_Burns]

Funny that you mention that Roy. I had a similar incedent yesterday on a 1900kW process filter fan for a coal gasification plant we are building in South Korea. It's easy to reverse the direction on a three phase motor. The problem starts when it is fitted with a uni-directional cooling fan for optimized noise emission reduction. Luckily it was still in the factory and not on site when it was discovered.
Regards
Declan

[bmcecosse]

Unfortunately my cooling tower was left for me to find the problem........

[Declan_Burns]

Same in my case!
Regards
Declan