2 speed wiper switch

[1750GTV]

The wiper switch in my 1750GTV gave up the ghost quite a while ago and I ordered a new one from one of the usual suppliers in the UK.

My wipers are two speed with the usual foot switch. It was working perfectly up until a couple of years ago when the low speed stopped and only the high speed would function.

The wiper motor has three wires - green, white and red. If I directly power the green wire I get high speed, both the green and white, low speed and the red parks them, so the motor is doing everything correctly.

The new switch has 8 connectors on the back ( labeled 1 to 8 ) and no matter how I connect it, at best I can only get the high speed plus park function to work. The old switch was the original one. It had only 4 connectors on the back, the other 4 having no connection lugs. Unfortunately it is not reparable.

The wiring diagram in the Haynes manual is useless as are a couple of pages that I downloaded from the AlfaBB - they describe connections for a two speed four wire motor.

Has anyone had any success sorting this problem. It's starting to do my head in ...

Chris

 

[Craig_m67]

Yes, it was a like an ice cream brain freeze at times, but yes

I'll see if I can scare up my wiring diagram
You should also search the US Alfa BB for relevant threads

In the end, my wiper motor was rusted solid.. which didn't help diagnose the switch

[1750GTV]

Thanks.

I've already searched both the US and UK bulletin boards to no avail. Lots of stuff for later models though, none of which is applicable to me.

I'll map out the internal switch connections on the weekend - that will be a start.
At least the wiper motor is still in good nick.

If you have any more ideas or suggestions, please post them.

Chris

[Paul Byrne]

Yes its a thorny one. Finally got it sorted with the 8 connection switch. There is no connection arrangement which will do the job properly. As close as you can get without add-ons is for everything to work but the slow speed setting is incorrect in that both high and slow speed motor wires should be energised in slow mode, however the switch can only be set up to apply power to the slow wire and not the fast one as well.

This problem is then fixed by adding a relay and a diode.
Connect the relay coil pin (86) to switch pin 3 (earth the other relay coil pin(85)).
Connect the relay contacts (normally open) across switch pins 1 and 2.
Connect a 5 amp, or more, diode across switch pins 3 and 7, with the painted bar at the seven end.

Now all is correct. Quick run through of switch connections other than above, colours refer to the connections at the plug coming from the motor, not the actual wires going into the motor:
1 goes to high speed motor wire (gray) and to foot switch plug (gray)
2,4,6 are connected together
5 is connected to 12 Volt source
7 is connected to slow speed motor wire (blue)
8 is connected to foot switch (blue white stripe)

Remaining connections are:
Other Blue/white from foot switch goes to motor plug
Blue/black from foot switch goes to motor plug and to 12 volt source.

I used a 75 motor and relays driving the motor to make sure we had plenty of grunt for rally conditions but the standard set up without all that will work fine. Might be an idea to up the diode to 10 amp just to be on the safe side if using unassisted switch.

[1750GTV]

Got it sussed.

To recap -
The car is a 1970 1750GTV fitted with a two speed Bosch wiper motor.

The three wires that come out of the wiper motor maybe different colours to those shown in my car but connect to the traditional colours in the wiring loom via a four pin connector.

The new 8 pin style switch is connected as follows:

Power (+12V) comes in on the blue/black wire and it's connected to Pin 4
The blue wire is connected to Pin 3
The white/black wire is connected to Pin 5
Pins 4 and 6 are connected using an external jumper

I worked this out by powering the leads to find which did what and then used an 8x8 grid which I filled in using a mulitmeter to test the internal pin connections with the switch in each position.

This works for my car. I have the wipers parked when the switch is in the up position, low speed when it's in the middle position and high speed with it in the down position. The foot pump sweeps the wipers at high speed and parks them when you lift your foot.

Hope this helps.

Cheers,
Chris

[Paul Byrne]

Good that you have that sorted!
I can't tell from your description, but are both the high speed and slow speed motor wires energised in the 'slow position? I could not get the switch to energise both without the relay/diode mod described above. The slow mode will work with only the slow wire connected but motor will have much less torque.

[1750GTV]

Hi Paul,

When the switch is off, the blue/black (+12V) wire is not connected to anything. The wiper motor receives voltage directly to the (in my case) red wire which parks the wipers.

With the switch in the middle position, pins 3 & 4 and 5 & 6 are interconnected. With the jumper linking pins 4 & 6, voltage in applied to pin 5, the white/black wire (-> white wire on the motor) and to pin 3, the blue wire (-> green wire on the motor). This activates low speed.

With the switch in the on position, the only two pins connected are 3 & 4 which supplies voltage to the blue wire (-> green wire) and activates high speed.

Some of the wiper motors are colour coded green, yellow and white rather than white, green and red. In that case green maps to white, yellow maps to green and white maps to red. 

You can see why I was a little puzzled ...

For me, the key was identifying which wire did what and drawing the 8x8 grid of switch connections. Makes cryptic crosswords a doddle.

Cheers,
Chris