• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

TR4/4A Wiper 2-speed switch wiring 4a

Share this page

H

HarryL

Jedi Trainee
Offline
Another wiring question for the 2 speed switch.
Have 3 wires black, red/lt green, & brown/lt green.
The back of the switch is a rectangle with spades numbered 1,4,6,7,8.
There are other numbers but with no spades. Number 1 is on one end of the
rectangle with 7 & 8 opposite side. 4&5 are in a cube extended away from the base
of the switch. Trying to figure where those 3 wires go. Any help would be greatly appreciated.
Harry
 
I'm pretty sure it's black on 1, R/LG on 4 and N/LG on 8. The other tabs are unused.
 
By normal Lucas standards black = ground, red/lt green is low speed to motor, brown/lt green is park, also to motor.

You seem to be short a few wires! Typically, blue/lt green high speed to motor, and you also need a live in to the switch.

There should be 5 terminals on the motor, arranged:

.....................................Black Ground

High Speed Blue/lt green................................Park Brown/lt green

Low Speed Red/lt green.................................Permanent Live (usually green)

Hope this helps! I'm not a Triumph guy really, but many old British cars follow the same routes.
 
That's a later motor, Roger. On the wiper motor used on a 4A there are only 3 wires to the switch and only the motor gets power. Black is ground, R/LG is low speed and N/LG is high speed.

DR3A 2 speed wiper motor.jpg
 
That switch must be used for a lot of applications because there are more terminals on the back than you need, it took me a few trys to understand how the motor worked and what the switch controlled. Once you get the concept that the motor is powered and the switch controls the ground circuit then it's a matter of determining which posts were to be used at the 2 switch positions to get slow or fast speed wipers.
Glad you got it figured out.
 
Yep. Used on many makes; and Triumph used it in various places for 2-speed heater and for headlights. Curiously enough, Stags use the same switch for the heater fan; but when factory A/C is installed, use the same switch but with terminal 2 installed instead of terminal 4.
 
JerryVV said:
Randall, do you have drawing of the switch internals showing which terminals are live in the 2 on positions?
Click to expand...

Just this for the switch logic:

Off 1 - 6 - 7
Low 1 - 4 - 6 - 7
High 1 - 4 - 7 - 8

Since the switch grounds the motor leads to make it run, terminals 4 and 8 would be 'hot' in the off position (but with the key on), supplied not through the switch but through the motor. For low speed, terminal 4 would be grounded, leaving some voltage on terminal 8. Then for high speed, 8 is grounded as well.

Oops, wait a minute, how about this (ignore the 'heater' label, it's the same switch) :
untitled.JPG
 
My head is going to explode! A few years ago when I was almost finished with my restoration I spent an excessive amount of time figuring out which terminals to connect the 2 wires from the wiper motor to on the back of the switch. It works fine but that exercise was frustrating. Once I relized that I was controling the ground via the switch and not the power it all started to make some sense. I don't understand the 1 to x to x notations however. Is that to say that in that position those terminals are all connected inside the switch?
 
Gee, Jerry, I'd hate to be responsible for your head exploding!

But yes, that is what it means. With the switch in the off position (fully in), terminals 1, 6 and 7 are connected inside the switch. For low speed (center position IIRC), terminals 1, 4, 6 and 7 are connected within the switch. And for high, terminals 1, 4, 7 and 8 are connected.

So, in this case, terminal 1 is grounded. Terminals 6 and 7 are not used, so we can ignore them.
For low speed, terminal 4 is connected to terminal 1 so it is grounded and the motor gets ground through the R/LG wire. (This is the same circuit that gets completed by the 'park' switch in the motor, to return the wipers to the park position after the key is turned off.)
For high speed, terminal 8 and hence the N/LG wire is grounded as well. This shorts out part of the field winding, which has the rather unexpected effect of making the motor run faster. For the sake of Jerry's head, I'd best not explain why :smile:
 
Back
Top