Diagnosing and fixing a wiper fault.

[Reuben]

Little thread showing how i'm going about fixing my dead rear wiper. This can just as easily be aplied to front wipers, or any electrical fault.

Symptons, the rear wiper does not move at all. No noise from the motor.

Possible causes:
Blown fuse
Dead relay
Dead driver switch
loose connection
Totally dead motor
Broken wire (common in wagons)

How can we find what it is? By using a multimeter!

First port of call is always the fuse box. In this case, I've found no blown fuses.

Next, finding out how the system works, and for that we need to look at a wiring diagram to find out.

Now the wiring diagram actually has diagnostic proceedures listed. It's method is buy suppling 12v from a battery to certain pins, and test if continuity exsists from others. By supplying your own power, you can say, directly power the motor, if it doesn't move, problem solved, it's the motor. Directly power the relay, if you don't get continuity across the other pins, problem solved, it's the relay. Etc.

It is possible to just use the cars own electrics to supply that voltage, but it makes it harder to track down where the problems lay, but to test the motor for example, all i need to know is which pin the motor gets power on, and if it's getting power on that pin and not moving, solved...

Next we start testing...

[Reuben]

I started with the motor, the motor has a 4-pin plug, which should have a constant 12v on pin 1, and ground on pin 3 with the keys in the accessory position. I tested this, and I do indeed have power, and the ground is solid.

The manual says to test the motor works, supply power to pin 2, and ground to 3. So i pilled pulled pin 1 and 3 out and used the cars power, and supplied 12v to pin 2, and ground to pin 3, and low and behold, the wiper moved for the first time in YEARS. And it's perfect. The manual then says to test auto-return by having power on pin 1, ground on 3, and by bridging pins 2 and 4. I did this, and auto return works fine.

https://sl-i.net/FORUM/images/imported/2012/11/IMG_5157-1.jpg


So, the motor has power, so that means no blown fuses
The motor also works, so no blown motor.

Next step, test the switches...

And they came up fine.... The manual lists what pins should have continuity between them with the switch at various positions, so simply probe, set to beep, and toggle swithces, that easy...

https://sl-i.net/FORUM/images/imported/2012/11/IMG_5161-1.jpg


So if it's not the motor, not the switch, not the fuse, and there is the constant power going to the wiper, it must therefore be the relay. A simple fix. Except it took 2 hours to find it!!! I eventually found in the manual that the relay/intermittent controller sits on the right had rear strut tower in the wagons, so I checked there in the sedan, and found nothing. I eventually tore the whole boot lining out, to find it sitting bolted innocently to the rear washer fluid tank, below the right tail light...

So having located it, I extracted it, tested it, and found to be faulty.

I hooked it up to the battery, and it clicks away happily, I tested the continuity, as per the manual across the right pins when it's open, and when it's closed. The continuity across the pins that should be live when switched on was not there, I tested the resistance, and it's at about 10ohms, when across the other pins while open, they only got 0.5 ohm

Excellent, ordered one in and I shall have a working rear wiper once more! Was a great afternoon and I learned a lot about how to use the manuals to test electronics, and how to use my multimeter.

https://sl-i.net/FORUM/images/imported/2012/11/IMG_5163-2.jpg

Resistance across the active pins when closed:
https://sl-i.net/FORUM/images/imported/2012/11/IMG_5164-1.jpg

Resistance across the active pins when open:
https://sl-i.net/FORUM/images/imported/2012/11/IMG_5165-1.jpg