ausmini
https://www.ausmini.com/forums/

Converting early SQUARE wiper motor to 2 speed
https://www.ausmini.com/forums/viewtopic.php?f=5&t=40567		 Page 1 of 1
Author:  drmini in aust [ Sat Mar 29, 2008 6:15 pm ]
Post subject:  Converting early SQUARE wiper motor to 2 speed
I had another play with my spare 850 wiper motor and a multimeter today, to see what speed I could get from it.
I have an ex-Fiat 124 Sport wipers 0-68 ohm variable resistor wired into the field circuit.
0 ohms gave standard speed, increasing it up to 22-27 ohms gave more than a 2x speed increase.
At 35 ohms it was no faster than at 27 but had insufficient torque to start. :cry:

So....
If you want 2 speed wipers here's what to do:
1. cut one of the field wires and solder some 2 core flex to the 2 cut ends.
2. run the flex out to an on/off switch.
3. wire a 22 or 27 ohm, wire wound 10W resistor across the switch too.

With the switch ON you will have standard speed, with the switch OFF you will have approx 2x standard speed.

BTW I didn't just make this circuit up, I copied it back in 1967 from a Popular Mechanics? magazine, it worked in my 850 back then too. :wink:
Image

Why does it work? I'm not an electronics guru so I don't know, but it does. :lol:

<edit> typos- I had ON and OFF arse about. :!:
Author:  jasonf [ Sat Mar 29, 2008 7:42 pm ]
Post subject: 
Thats awesome Doc, just what ive been looking for and saves having to do a conversion, very handy howto :wink:
Author:  gafmo [ Sun Mar 30, 2008 6:32 pm ]
Post subject: 
we'll do a little more work on this and make it into a "How to"
:wink:
Author:  Harley [ Sun Mar 30, 2008 6:37 pm ]
Post subject: 
Why the resistor would make the motor twice as fast I don't know (Would suggest a relay in the circuit so the factory switch doesn't take twice as much current), but when the switch is ON the circuit takes the path of least resistance, so thats why things are normal again.
Author:  drmini in aust [ Sun Mar 30, 2008 6:42 pm ]
Post subject: 
Harley wrote:
Why the resistor would make the motor twice as fast I don't know (Would suggest a relay in the circuit so the factory switch doesn't take twice as much current), but when the switch is ON the circuit takes the path of least resistance, so thats why things are normal again.

The current draw is actually less when the motor is running fast.
I know how the switch works (it shorts the resistor), what I don't know is why adding field resistance speeds the motor up. :?
Mick, where are ya buddy... :lol:
Author:  Harley [ Sun Mar 30, 2008 7:02 pm ]
Post subject: 
Adding resistance to the field would send more power to the armature, so it spins faster, but if the current is less, then there should be less torque as a result, or something. I'll shut up now and wait for a sparky.
:D
Author:  slo_firo [ Mon Mar 31, 2008 5:39 am ]
Post subject: 
your right - more resistance = higher speed,

i cant explain right now as im sleepy lol..... and would have to read through some of last years notes
Page 1 of 1 All times are UTC + 10 hours
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/