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TR250 wiper motor wiring

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Aphyle2012 Avatar
Aphyle2012 Silver Member Eric Pyle
Shenandoah Valley, VA, USA   USA
The Clear Hooters switch for the TR250 should have three terminals, F, S, and the center one.

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Fictioneer Avatar
Fictioneer Doug Hirt
Colorado Springs, CO, USA   USA
I think Randall has it right. The motor looks to be assembled from two different motors. The motor part itself a single speed unit and the gear section, or at least the top plate, from a later motor.



"Mr. Filby, do you think he'll ever return?"
"One cannot choose but wonder. You see . . . he has all the time in the world!"

TR250Guy Avatar
TR250Guy Tim Moore
Dayton, Ohio, USA   USA
1968 Triumph TR250 "TRminator"
This is what the back of a TR250 wiper motor looks like. The 4 prong switch is a TR6 switch which they sell as a replacement since the 3 prong are unobtanium. However I have no idea how to wire it to a TR250 wiper or if its even possible.



1968 TR250 "TRminator"
Owned since 1980
Frame off rotisserie restoration completed in 11-2014 by myself and my brother

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Aphyle2012 Avatar
Aphyle2012 Silver Member Eric Pyle
Shenandoah Valley, VA, USA   USA
Agreed. I tried it without success, but then that is not my strong area. There may be a way, but I just don't know it yet. I found that I could disassemble and repair my existing 3-prong switch, and then found I had a spare. I was working up a 3D print model to make a replacement, but no one else showed an interest, so the project went on the back burner. The nice thing is that the Clear Hooters switch body halves, while complex, are identical, not mirror images.

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
In reply to # 1449037 by TR250Guy However I have no idea how to wire it to a TR250 wiper or if its even possible.
Offhand I can think of 3 ways to make it work, but all involve some added components. Probably the simplest is adding just a big diode, but it would have to be big enough to handle the armature current under all conditions. 15 amps might do, but I'd feel safer with 20. One of these http://www.ebay.com/itm/like/181829236483?lpid=82&chn=ps&ul_noapp=true might do, or an old alternator diode if you happen to have one lying around.

A common SPST relay and two smaller diodes would work also. 2 amp diodes should do (or one could be even smaller if you want).

Or, I believe the starter/bulb test relay from a late TR6 could be used without the diodes.

The problem is that the 2-speed version of the DR3A requires that two terminals be grounded for operation on low speed; while the TR6 wiper switch only connects one terminal at a time. So the extra circuitry is to ground the other terminal when the switch is in the low speed position.



Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild



Edited 1 time(s). Last edit at 2017-04-12 12:13 AM by TR3driver.

Aphyle2012 Avatar
Aphyle2012 Silver Member Eric Pyle
Shenandoah Valley, VA, USA   USA
Randall,

I knew someone would have a solution. Part of the problem, as you rightly point out, is the grounding of both terminals for slow.

This is counter-intuitive, if you read the thing that I shared in Post #4, it becomes more clear, and for On the surface, one would think that you just shove more electricity in to make the motor spin faster. But really, it is about shoving less electricity through the field coil that makes the armature spin faster. More electricity through the field coil makes it go slower, IIRC. Hence the resistor wire inside the motor for two-speed motors, or the external solution that I devised. Incidentally, had I not found a proper two-speed motor to rebuild, my plan was to use the converted two-speed with external resistor. The resistor would have been mounted out of sight with no modifications to the wiring loom.

I'm convinced that my one-speed motor was a replacement, as the car was made in late 1967/early 1968, but had 7/64 on the motor cover plate.

Best of luck!

MonAndrew77 Avatar
MonAndrew77 Andrew M
Northern, Virginia, USA   USA
Oh brother. Well at least I know what I need. Thanks everyone.



So I'm assuming this would solve all my problems and then I'd just have to find a switch..... sad smiley

http://www.ebay.com/itm/RARE-TRIUMPH-TR4A-TR250-1966-69-TWO-SPEED-LUCAS-75568-WIPER-MOTOR-REBUILT-EXCH-/382015263316?hash=item58f1e25254:g:5FcAAOSwgQ9VjWU4&vxp=mtr

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Fictioneer Avatar
Fictioneer Doug Hirt
Colorado Springs, CO, USA   USA
Andrew, the auction says it requires a core of the same type of motor. I'd contact them to see if they'd take yours in exchange, but they sound pretty adamant.
Doug



"Mr. Filby, do you think he'll ever return?"
"One cannot choose but wonder. You see . . . he has all the time in the world!"

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
In reply to # 1449095 by Aphyle2012 This is counter-intuitive, if you read the thing that I shared in Post #4, it becomes more clear, and for On the surface, one would think that you just shove more electricity in to make the motor spin faster. But really, it is about shoving less electricity through the field coil that makes the armature spin faster. More electricity through the field coil makes it go slower, IIRC.
This motor is what is known as a parallel (or shunt) wound motor; meaning the field winding gets fed directly from the input rather than being in series with the armature. Parallel wound motors have a self-regulating speed characteristic, caused by a thing known as "Back EMF". Basically, even though it is running as a motor, it also acts like a generator and generates a bit of voltage that opposes current flow through the armature. The faster the motor spins (for a given field current), the more voltage it generates and the less current flows through the armature. (If you spin it fast enough, the current will reverse and it will become a generator.) Less current through the armature means less magnetic field, and less torque generated, hence the self-regulating speed characteristic.

So, cutting down on the field current reduces the Back EMF that is generated and raises the natural (no load) speed. As long as the motor can still make enough power to overcome the drag in the wipers, that also raises the loaded speed. But you aren't getting something for nothing, the armature current also goes up.



Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

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