Wipers - The wiring

Paul.....you're gonna love this one!!!!


Before I start on the switch side of things I need to get the wipers basically functioning from the components I had and in their standard "from the factory" form i.e. unmodified.

Again I harp back to all the work I did labeling wires and tracing circuits when I pulled the front loom apart to sort out the aircon wiring. This was invaluable once again with working out what went to where for the wipers, so I got them going without too much trouble.

Remember though I now needed to change the Toyota wiring over to the Holden Vectra Wiper unit. Different brands and one was Japanese design while the other was European design, so matching wire colours etc was not an option at all. Luckily though most systems work in a very similar way, so sorting out how five wires married up with another 5 wires wasn't too bad....going back to my statistics days at high school if you have five wires to join, there are 5 x 4 x 3 x 2 x 1 ways they can go together that's right, only 120 different ways you could connect them. OH NOOOOOO!

Actually no it wasn't that bad. The earth wire had a bolt through it so was obviously the earth.......so we are down to 4 x 3 x 2 x 1 combinations. Only 24!

Then by making a circuit from the earth to each of the other wires and touching it with ah a 12 volt power source I was quickly able to find slow speed and fast speed. So now I only have two wires to figure out. One would be a permanent power on wire and the other is a wire from the park position switch. It was a pretty quick inspection of the unit to decide which was which.

IMPORTANT NOTE. THE ONLY REASON I COULD EXPERIMENT LIKE THIS IS BECAUSE THE WIPER MOTOR WIRING IS HEAVY AND ONLY GOES TO A MOTOR WHICH AGAIN IS QUITE STURDY AND POWERFUL.....NO CIRCUIT BOARDS.....NO TRANSISTORS....NO RESISTORS.....NO CAPACITORS.....so I couldn't really do much harm. You WOULD NOT do this without being sure of what you were dealing with.



Ok with that out of the way, lets head inside the car now to look at the switches. Most cars these days have a wiper stalk on the steering column that will generally look like this.

This one is from........you guessed it.....a Toyota Celica!  It moves up and down to select intermittent, slow and fast. When you are on intermittent, you turn a ring halfway along to control the delay between sweeps 2.5 seconds, 5 seconds and 7.5 seconds. Lastly there is a button on the end to activate the washers and two sweeps of the wipers.

All this is controlled by the switching mechanism and circuit board that is hidden inside the steering column.

It is quite a complicated set up and I'm about to make it even more complicated by trying to retain all this functionality while converting it to a rotary switch with a knob so I can have it match with all the other switches I will be using. Also because I don't want an ugly stalk on the steering column. The plan is to have a panel in the centre console with all the switches in it and a door than can be closed when you are not driving.

As I said above I really want to keep all the functionality. Its not a requirement of the cert process, all you need for that is two speeds, but I have had my days of driving modified cars where if you wanted intermittent you had to turn the switch off and on manually. I also want self parking (where the wipers automatically stop at the bottom of the screen) as it is a pain in the proverbial having to hold your mouth right and count the sweeps of the wiper in a bid to try and time turning the wipers off when the arms are at the bottom of the screen.

So here goes my attempt at the conversion.....we'll look at the off, intermittent, slow, fast switch first of all....

This is it here. The arm you pull down on, pivots in this housing and moves the two brassy looking contacts (at the top right hand side of the above picture) with four distinct clicks for off, intermittent, slow, fast. These contacts in turn make contact with terminals on the circuit board when the unit is assembled.

The pointer is showing you the two rows of terminals. The first row having 5 contacts and the second has just 3. There is a smear of grease in here to reduce wear and for smooth operation.

Now what I hoped to do was to use all this as is. I removed the wiper stalk so the unit now looked like this.....

The screwdriver is in the hole where the stalk came from and I can now still make it work just by moving the screwdriver up and down. Remember though I want a rotary switch. So what I did was remove the arm inside the unit, the one that has those two brass contacts on it. Here is a close up of it.

I drilled a hole through the pivot point at the other end and cut a thread so I could screw in a bolt to use as a shaft. The idea is when you turn the shaft (imagine a knob on the end of it) the arm rotates to the 4 different positions to make contact with the terminals I showed you earlier.

Here is the shaft now in place.

It kind of worked okay when I put it all back together except with a wiper stalk you have a lot more leverage than you do with a knob that is at the actual pivot point. In essence it worked okay but was very stiff.

So what I did next was look at ways to make the switch "softer" to operate. Firstly there is the divisions inside the housing that hold the switch into the various positions off, int, slow, fast. They are the 3 peaked ribs you can see in the back of the housing in this next picture. The switch clicks into the gaps at either end and between the ribs i.e. 4 positions.

I could try and file or sand these down a bit, but that would be quite hard so I decided to look at the other part that clicks backwards and forwards over these ribs. This is actually located in that arm with the brass contacts and it consists of a nylon "nib" that is pushed outwards by a small spring. The nib then is forced against the 3 ribs shown above and of course it naturally wants to be in the gaps at either end or between the ribs, so it clicks into one of the 4 positions.

By reducing the pressure on this nib when it is going across the ribs, the switch will be softer to operate. I did two things to achieve that....I filed a bit off the nib, it wasn't enough, so I filed a bit more off....still not enough, so I then cut one coil off the spring. It was getting softer but still a bit tight. Another half coil off the spring and it was pretty good....trial time!

Regrettably, my plan, while it worked, wasn't quite as good as I would have liked. Firstly the shaft had to protrude out through the back of the switch as the unit screws onto the circuit board as I showed earlier and you cant drill through a circuit board without buggering up the circuits. What this meant is that the switch operated in an anti clockwise motion so where you'd expect to find off, the switch was actually set to fast and vice versa. That would just be bloody annoying.

In addition to that the switch was still very difficult to operate. The spacing between each setting was very small so it was easy to inadvertently go from off to fast when all you really wanted to do was go to intermittent. Again this would just be bloody annoying. A back to front switch with a hair trigger....that can only spell disaster! Back to the drawing board it seems.

My next option is to buy a switch and wire it to the circuit board so that the different positions of the switch mimic the two brass contacts sliding over the terminals. You see what those two brass contacts do is they each bridge across two terminals at a time.

On the top row the contact bridges terminal 1 & 2 in the off position, when its on intermittent it bridges terminal 2 & 3, slow = terminals 3 & 4 and fast = terminals 4 & 5.

Meanwhile the bottom row the contact bridges terminal 1 & 2 in the off position, when its on intermittent it bridges terminal 2 & 3, when its on slow it bridges 3 & a blank position (no circuit is made) and on fast it sits wholly on the blank position (no circuit is made)

So in a diagram you can see what I have mentioned above.

The black dots are the terminals. between them I have drawn brackets to show which terminals are connected in different positions. You can see the different settings labeled as well, off, int, low, high.

At the top of the picture I have keyed these to numbers 1, 2, 3, 4 in circles. Now what has to happen is I need a switch that has 4 positions obviously off, int, low, high but it is more complicated than that as it needs to make two circuits at once, just as the two brass contacts did on the original mechanism. When in the off position for example I have to connect the first and second terminals on the first row and at the same time connect the first and second terminals on the second row.

To do this you need what is known as a multi pole switch. And here is one shown. In the picture I am putting a circuit tester on to Pole A and Terminal 1.

The circuit tester has a setting that lets it emit a beep when a circuit is made. By doing this I can set the switch to each of the 4 positions and I can then test to see which terminals make a circuit in each one of those 4 positions. The diagram below shows the layout and markings for the terminals.

As you can see there are 12 terminals around the outside and three "poles" (hence multi pole switch) in the centre. When the switch is in the off position A makes a circuit with number 1, while B makes a circuit with number 5 and C with number 9. Then when I go to the next position with the switch the circuits all move round 1 position also, so A makes a circuit with number 2 now, B with 6 and C with10. They then all move round one more with the switch in the third position and again when I move the switch to the last position.

So what I decided to do was to put them into table form so I could easily see what was happening.

Here is my simple table. The positions of the switch 1 to 4 are listed down the left hand side. You then read across to see which terminals are making a circuit in that position i.e. in position 3 Pole A is making a circuit with terminal 3 so A-3, B has a circuit with 7 so B-7, then of course there is C-11.

Lets go back now to the terminal diagram.

It gets a bit tricky here as the terminals don't get used exclusively i.e. the second terminal in the top row for example is bridged with the first terminal when the switch is off but it is also bridged with terminal 3 when it is in the Intermittent position, so it used twice for different purposes.

The big thing I had to work out here was how to ensure I kept things separate so there was no circuit crossover (shorts). It took a bit of thinking but the numbers along the top and bottom of the terminals shows the combinations I eventually came up with.

I then cross checked this back to the table to make sure everything aligned.

The outlines drawn around the "letter/number combinations" represent the circuit being made. You might remember earlier I mentioned that the bottom row of terminals only made circuits in position
1 = off and 2 = intermittent. After that the contact moved off to a blank and didn't make a circuit any longer.

So looking at the picture above in position one I made a bridging circuit across the first two contacts in the top row using Pole A and terminal 1. At the same time I bridged the first two contacts in the bottom row using Pole C and terminal 9.

A-2 and C-10 were used in position 2 = intermittent.

Then in position 3 only the top row of terminals are bridged using B-7 = slow. Then lastly position 4 fast = B-8.

Okay in theory but what happened next?????????

Lots of soldering and checking and double checking with my diagrams and tables and here is the final result. An octopus of wires soldered to the back of the appropriate terminals......

.......and the other end of them soldered to the appropriate poles and terminals of the switch.

Now all I needed to do was hook the wiring up to the wiper motor and listen for any nasty fizzling and crackling sounds as things shorted and sparked......but no.......all was very silent.

Click the switch to intermittent......yes! Slow......yes! Fast......yes! It worked, my planning had paid off!

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