[TR] TR] 2-speed wiper wiring diagram

[Ed Woods]

Anyone that's still interested,

Spent the evening trying to figure out how the 2 speed wiper worked. Finally 
figured out the that second "winding" isn't a field winding at all. It's 
just a resistance wire that, when it's in series with the field winding, 
limits the current through it, weakening the field and producing the high 
speed mode. This high speed mode is produced by grounding only the red/light 
green wire. When both the brown/light green and red/light green are 
connected to ground simultaneously, the resistance wire is shorted, the 
shunt field current is increased because it now has a full 12 volts across 
it, and the motor runs at slow speed.  Another clue to the function of the 
resistance wire and proof that it is not a field winding is that it cannot 
in itself cause the motor to turn, even w/o a load. This condition is 
produced by connecting only the brown/light green wire to ground. When you 
do so, nothing happens. Well, it does hum, draws a few amps, but doesn't 
turn.

Took me a while, but age has something to do with not being able "think 
outside the box". I kept trying to make sense out of my observations based 
on the supposition the both windings were field windings. They're not.

I have tested 3 of these motors. All work in the same manner.

If you check out the dash switch on a TR4A or a TR250, I'll bet that the 
first position, the "slow" position, connects both the N/LG and R/LG wires 
to ground. The second position, "fast", only the R/LG to ground.

Ed


----- Original Message ----- 
From: "carlsereda" <carlsereda at aol.com>
To: "Geo Hahn" <ahwahnee18 at gmail.com>
Cc: <triumphs at autox.team.net>
Sent: Monday, September 28, 2009 10:23 PM
Subject: Re: [TR] TR] 2-speed wiper wiring diagram


>I don't know if you have a field winding with pos/neg going one way, and 
>you
> overlay it with minor secondary winding with the opposite polarity - what
> happens.. does the magnetic force field gets stronger or weaker?
> I took a peek inside the 2-speed and it actually has only 10 loops of
> overlaying winding, not 50 like I thought, but I can't tell the 
> polarities.
> A few years ago I was wondering how could a mere 10 additional loops of 
> wire
> (thread insulation) on top of  about 100 standard loops (lacquer 
> insulated),
> could speed this motor up - but ahah, after Tony's info today - I'm 
> thinking
> it may slow it down!
> Please, somebody tell us the answer!
> Regards,
> Carl
> '63 TR4 since '74
>
> I think I liked your first explanation better (that the additional
> windings increased the strength of the field and the motor's speed).
> Since the 1-speed motor has it's hot lead always on and the switch
> controls a ground it would not surprise me if on a 2-speed motor both
> windings were always connected to a hot lead and the switch controlled
> whether one or both were grounded.
>
> Interesting & mysterious.
>
> Geo
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