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TR4A Wiper switch Terminals.


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I am now at the stage of connecting up everything behind the dash. While I know that I have a black, Brown/LG & Red/LG to connect I do not know which terminals on the 2-speed switch to connect them to. The switch has terminal 1, 3/4, 5/6 , 7 & 8. None of my books/wiring diagrams  show the terminal numbers. Any help would be appreciated.

cheers,

Allan

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AlanT will doubtless be along to give you the definitive answer.  There’s an image on the forum somewhere. 

Edited by peejay4A
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There are several ways to wire the switch which kind of work but really are wrong.

One has you parking at FAST speed which as mentioned above can mean that it jumps over the gap in the parker and goes off again or just parks past where it should do.

Another little variation has the motor behave perfectly but even in the PARK position current continues to run through the field-coil.  It stops of course when you turn off the ignition but otherwise your motor is kept warm all the time.

You can also get it so that the switch gives PARK-FAST-SLOW rather than PARK-SLOW-FAST.  This just means that you are starting the motor at reduced torque.  A bit like pulling away in 3rd gear. Sometimes they stall if you do this.

If they stall and you don't get power off quite quickly you will get a "black-wire" armature.

 

 

 

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  • 1 year later...
On 4/5/2020 at 8:56 AM, AlanT said:

I got the RED and BROWN wires in the wrong place in that copy of the pdf.

Anyway the photo shows where the wires go.

I've posted this photo several times on here.  But somehow it never gets found.  Maybe it will now.

 

34477-3.jpg

Hi Alan, having done searches on UK and US TR sites I am thoroughly confused as to which is the correct set up for the 4a wiper switch, I have found at least 4 different recommendations. In your pic above could you confirm that your red=Red/LtGr and brown=Brown/Lt Gr and black is earth?

One of the alternative suggestions was Black to 1 or 7, Red/LtGr to 4 and Brown/Lt Gr to 6....confusing

Many thanks

David

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Hi David,

 if in doubt use a multimeter or bulb to see the pattern of the switch positions.

 

With pin 4 as earth and the knob pulled to the first click pins 6 & 7 should be be shorted to pin 4  (fast speed)

In the second click position  Either pin 6 will be shorted to pin 4 or pin 7 will be shorted t pin 4 (Slow speed)  but not both.

In which case the other wire will be open circuit.

I'm sure that Green/Red is for slow and will be shorted to pin 4

This information can be transferred to the motor

 

Roger

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Thanks Roger, electrics not my strongest suit, but I guess what I'm struggling with is why there isn't one straight answer to this; there must have been a std red wire to terminal X etc when built, but every time the question is asked there is another slight variation on the answer. Does that mean there is a better way of doing it, or a number of ways of doing it? 

Confused

David

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Hi Roger and Alan

Now I am confused. For 30 years the wipers on my 4A are Park, Fast, Slow but Alan says It should be Park, Slow, Fast and Roger you say opposite. So is it first pull position Slow or Fast?

Just consulted the Triumph 4A handbook. On page 7 it is first position fast speed and second position slow (as I have it).

Keith

 

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Hi Keith,

the first click is FAST. This is not ideal as this also has the lowest torque

The second pull is slow - this gives the highest torque and allows the wipers to move across a dry screen (just)

This is not intuitive.

I'm sure I had my wipers going slow on the first pull and fast on the second.

I'll have a look at my drawings tomorrow and see what  I've done.

 

Roger 

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Mine’s not like that Roger. I followed Alan’s advice and it’s first pull for slow, second pull for fast. This also means that you start on full torque and don’t overrun the park position when you switch off.  It might not be as the handbook states but it’s preferable. 

Edited by peejay4A
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Hi Roger and Alan again

Don't understand the torque argument. More power = faster speed. More power = more torque? The gearing on the motor is the same whatever speed. As you say on slow speed the wipers can struggle to wipe a dry screen. Has anyone measured the torque on both speeds at the wiper arm? Just wondering why Triumph should have wired the switch with first pull being fast if it wasn't preferable?

I had a dodgy connection on the wiper fuse that resulted in less power to the motor and it ran slower and eventually stopped as a result.

Keith

Edited by keith1948
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Hi Folks,

I have found an excellent write-up on the two speed motor Lucas DR3

It explains about how to increase the speed by reducing the field current

Why Lucas designed it to turn on FAST (first click)

The dangers of turning it on in the slow speed.

If you want it to turn on slow then using the standard switch I had the following wiring - 

Black - pin 1

Green/Red - Pin 6

Green/Brown - Pin 7

But this could burn out the fast speed field resistor.

I do not know who the author is but i think he did a good job.

Roger

two-speed xx.pdf

Edited by RogerH
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The force which makes the motor armature turn is magnetic, some is generated by the windings in the armature, & that force "pushes" against a mgnetic force generated by the field windings. The speed of the motor is governed by something called "back EMF" which is the voltage  generated by the action of the armature spinning within the magnetic field of the field winding. the faster it goes the higher the back EMF. when the back EMF is equal to the DC voltage being applied to the motor, the current drops, & the speed stabilises. When you select the fast speed, you are reducing the current in the field winding, thus reducing the magnetic force, & so the speed has to increase to bring the back EMF up to the applied voltage. but because of the reduced field the torque is lower.

Hope that makes sense.

Bob.

Edited by Lebro
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Hi Folks,

an interesting annoyance caused by the original switching is if you install  intermittent wipers.

These are normally connected to the slow speed. :o  Should the blades get stuck then you could  burn out the resistance wire.

Where will it end

 

Roger

 

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