wiper park switch: why does it connect to earth

I have spent ages trying to sort out the issue with parking my wiper motor.


I have a new switch at the drivers side of the car from Emberton Imperial (which has different pins to the OEM switch).
I had a new connector/parking switch also from Emberton on the wiper motor with 5 spades: 1) live feed in 2) live out 3) park 4) blank 5) earth.

Whilst I can get the motor to run (start/stop immediately) if I don’t have the park part of the circuit wired in, it all goes wrong when I set up the wiring fully i.e. it pops the fuse.

i.e.

- green on pin 1 provides power.
- Red/light green on pin 2 (slow, my motor only has 1 speed).
- Light green/Black on pin 5 for the washer.
- brown/light green also on from pin 2
And I have a new loom.


So, with the switch turned on, current flows to pin 1, through the switch to pin 2, and down red/light green to drive the motor.
My understanding is that when the switch is turned off,

• current would flow down to the connector/parking switch which initially would be closed so current would flow over to the brown/light green wire, back up to pin 2 and again drive the motor until
• the pin is pushed in, breaking the switch and everything stops.

But I can’t understand the actual behaviour of the connector/parking switch
1) when the pin is out (i.e. not parking), it connects live feed in (spade 1) to park (spade 4) – that makes sense
2) When the pin is in (i.e. need to park), it disconnects spade 1 and spade 4 (makes sense) AND connects spade 4 to EARTH pin(!).

By connecting spade 4 to earth, this means I have a live feed down the brown/light green wire that connects to earth – and it pops the fuse.
I dug out an old switch, and it does the same.

I can’t understand the point of connecting to earth – and I can’t find a way of connecting to the switch that makes the system behave as it should.

Sorry for the convoluted description – but the key questions are:

1. why does it connect pin 4 to earth and
2. how do you configure the wiring to work with this?

I haven't got a wiring diagram handy - could you put something up on here?

boguing said:

I haven't got a wiring diagram handy - could you put something up on here?

Click to expand...

So item 43 is the switch that sits on the motor. There are no pin numbers, but that doesn't really matter, as on the loom is a connector with the wires already connected in the right places.
The diagram doesn't show the pin switch that sits between pin 4 and 2.
My issue all boils down to the fact that when the pin is out, there is connectivity between pin 4 and 2 but when the pin is pushed in, this connectivity is lost and there is connectivity from pin 2 to pin 1 - and current flows down to earth and my fuse blows.
I cannot understand why the connection to earth is there.

Right, got my diagram out too. Just the same. Nice of them to show such amazing detail of the motor.

My first thought is that there is no reason ever to want to join any incoming V to the earth. - so is it possible that the connector fits some other way? A picture would help me!

My guess is that RLG and G are fast/slow or slow/fast and that NLG is permanent. The switch connects 2 and 4 so that permanent feeds slow/fast (whichever).

I have got this working. I am not sure if this is the best configuration but it works for me. This is single speed motor.

On the Emberton drivers switch (different pin numbers to the OEM switch and wiring diagram):
Pin 1:
G (live feed)
Pin 2:
RLG (feed to motor) and
NLG (wire back from pin switch)
Pin 5:
LGB (feed to washer)


On the Motor/Pin switch:
- plug the harness connector in
- take the black/earth lead and blank that off (i.e. do not connect to earth)
on the other side of switch
- plug the red wire from the motor to the lower back spade
- do NOT plug the blue wire from the motor to upper back spade (otherwise it blows the fuse) but DO connect this directly to earth.

The reason that the parking switch is a feed and then is connected to earth is that when the motor gets to homet it shorts out the motor windings. This action stops the motor like a brake. If it was to just disconnect the power occasionally when the motor came to park, inertia in the motor could keep it spinning and pass the park switch and complete another sweep.

PaulJM said:

The reason that the parking switch is a feed and then is connected to earth is that when the motor gets to homet it shorts out the motor windings. This action stops the motor like a brake. If it was to just disconnect the power occasionally when the motor came to park, inertia in the motor could keep it spinning and pass the park switch and complete another sweep.

Click to expand...

Not in any wipers I've worked on. The friction in the system stops the motor almost instantly.

Hi PaulJM. I can understand that and i can see the logic. The issue on my car is when it shorts it out, it pops the fuse. i wonder if this is somehow related to the drivers switch and if i had an OEM switch it might behave differently.
Given (as Boguing mentions) the motor stops pretty quick, i guess i am ok as i have implemented.
Hope this helps someone else in a similar position in future.