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PostPosted: Tue Feb 11, 2020 11:52 am 
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848cc
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A while back i bought the following heater from a forum member. Last weekend I finally got round to fitting it to my 1970 K.
I assume 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?

And another on my install method - please confirm
Connect one white wire to the black wire from the switch, green/yellow trace back to fuse A4, the other white wire earth to body.

Cheers, Paul.


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PostPosted: Tue Feb 11, 2020 12:00 pm 
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1275cc
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Joined: Wed Oct 03, 2007 9:04 pm
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Location: Melbourne, VIC
Hi Paul,

An interesting dilemma.

I can't answer your questions but in case it helps in the diagnosis I just checked the motor in my plastic 1970 Cooper S heater and the rotation reverses when I swap positive and negative leads.

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PostPosted: Wed Feb 12, 2020 10:28 am 
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1098cc
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Location: Camden
I seem to remember the motor turning the same way regardless of polarity in the wires on one of these some years ago.
This is what the factory put on them. I masked up the writing when I painted this one.


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PostPosted: Wed Feb 12, 2020 10:57 am 
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848cc
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Thanks Bill - clears up my questions nicely.

Cheers, Paul.


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PostPosted: Wed Feb 12, 2020 11:12 am 
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1098cc
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Location: Camden
Re your wiring questions:
Don't know much about electric motors - but starter motors also only turn one way regardless of earth.

The heater in my post does not have a green/yellow lead at all.
Yes. one of the 2 white wires connects to one of the black wires to the switch under the heater.
The other white wire from the motor goes to earth.
The Aust manual shows Power-in being picked up at Number 2 terminal on the ignition switch; the UK manual has it coming from the light switch terminal 7. Either way, it is a short distance.


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PostPosted: Wed Feb 12, 2020 11:28 am 
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1275cc
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Location: Melbourne, VIC
I asked the question on the Mk1 Forum in the UK. Thought someone on there may know.

http://mk1-forum.net/viewtopic.php?f=5&t=27733

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PostPosted: Wed Feb 12, 2020 8:38 pm 
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848cc
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Thanks for putting it out there Winabbey. Appreciate the help.

My heater motor spins the same way as that shown on Bill’s photo, so all is good for now though I would like to know the answer still.


Cheers, Paul.


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PostPosted: Mon Feb 17, 2020 11:44 am 
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998cc
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Joined: Wed Sep 22, 2004 5:46 pm
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Location: Melbourne
The fan should turn ACW at the fan end/CW at the motor end. The fan acts the same way as a centrifuge. It flings air out at the edge of the fan towards the air directional flap - Off - Screen - Car. That's why the fan housing is shaped like a spiral.
The DC motor has a field winding and an armature and if you reverse the polarity of the wiring it makes no difference to the direction of rotation of the fan. You are reversing both the magnetic field direction in the field winding and the direction of current flow in the armature so the fan spins in the same direction.
To reverse the direction of rotation you need to reverse the field connections without reversing the connections to the armature.
The MK 2 plastic bodied fan is probaly a permanent magnet motor. If you reverse the polarity of the wiring you are only reversing the direction of current flow in the armature as the permanent magnet field is not reversed so the motor spins in the opposite direction.
It's all to do with the reaction between the magnetic field in the field winding and the magnetic field in the armature.
(Current/amps flowing through a wire produces a magnetic field around the wire)

Hope this helps
RonR

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PostPosted: Mon Feb 17, 2020 5:30 pm 
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848cc
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Thanks Ron. All clear now.

Cheers, Paul


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