Mk 1 Heater Fan Direction Odd Polarity Problem

[Tds76]

A while back i bought the following heater. Last weekend I finally got round to fitting it to my 1970 K (Aussie Mini 1100 Mk2).
I assumed this heater was designed for a +ve earth car and also that it is a normal DC motor. My K is -ve so before installing the heater I checked which way round to connect it.

There are two wires from the motor - both white. I sat the heater on the boot lid and connected one wire each to the battery terminals - heater spun anti-clockwise (i believe it should spin clockwise). No problem I thought, just switch the wires around on the battery and all should be fine. Strangely the motor/fan still spun anti-clockwise. Assuming i'd made a mistake with my initial connections I reversed again - still anti-clockwise.

My fan will only spin one way regardless of the polarity. A quick Google followed...

So, questions:
1. Perhaps most important as it means I could avoid Q3: Which way should the fan spin when viewed from the fan side? CW or ACW?
2. Is the motor a 'brushed' DC - field windings in the stator as well as the armature?
3. If so, is the connection between the two fields easily accessed so that I can reverse it?


Cheers, Paul.

[Oneball]

I’ve wired one up incorrectly on a Land Rover and it spun the wrong way.

Perhaps it’s not a Smiths motor, take the side of the case off and see if there any markings.

[Tds76]

It’s actually installed and a bit of a pain get it in - esp the fresh air duct connection, so I was looking for answers to see if I needed to remove or not. Bill on the AusMini forum showed a photo of his heater with original labels and it shows only one direction. This is the same way mine rotates so all is good.

I had noticed in my googling that a number of the Smiths heaters show two different direction arrows to indicate how to connect for +ve or -ve cars. So maybe they used two different types of motor - permanent magnet DC or DC brushed depending on application.

Cheers, Paul.

[surfblue63]

The heater fan is a forward curved centrifugal fan so it needs to turn in the right direction as shown in the picture

Fan.jpg

[LarryLebel]

The motor has electromagnets rather than permanent magnets. When you change polarity the polarity of the electromagnets also changes so rotation direction stays the same.

[nick rogers]

Reversing the polarity of DC motors such as heater, wiper, starter will NEVER alter the direction of rotation. Anyone remember school physics ?