Technical Wipers won't stop

[littles]

Hello,

The wipers on my 2007 2.3 120 Multijet Ducato won't stop when the stalk is in the 'Off' position. They work perfectly in the intermittent, speed 1 and speed 2 settings but in the 'off' stalk position they go to speed 1. The fault is consistent when I turn the van on but if I drive for an extended period of time, it dissapears.

I've browsed the forum and it seems it could be caused by a faulty wiper motor, a fault/short to ground in the wiring from the BCM to the wiper motor, or a faulty steering column switch but open to other suggestions or feedback from people with similar issues. I'm new to electrical fault finding so some direction on where to focus my attention would be much appreciated. Some details on what I've done so far:

I've replaced the T12 relay for the wipers under the dash and that hasn't resolved it.
I've taken voltage readings on the 5-pin wiper motor connector. I got the following when the stalk was in the off position, is this what it should read?

Pin 2 = 12.1 V
Pin 3 = 0 V
Pin 4 = 0 V
Pin 5 = 11.5 V

Many thanks

 

[Anthony489]

Hi littles

The wiper function is as follows. The stalk switch varies its electrical resistance in steps between 0 and 2000 ohms. This resistance is measured by the Body Control Module (BCM) to determine what is being asked for. This seems a bit of an odd arrangement, but it means fewer wires are needed between switch and BCM.

The BCM then sends "logic" commands to the wiper motor on Pin 4 for On/Off and Pin 3 for Fast/Slow. When either of these lines goes low, it energises the appropriate miniature relay coil within the motor casing to select the required function. The relay coil live ends connect to 12 volts within the wiper motor, so if the lines aren't being pulled low by the BCM they will sit high at about 12 volts.

The wiper motor 12 volt supply is on Pin 2, and its Ground is on Pin 1

Also within the motor is a "park" switch on Pin 5 which goes closed circuit to ground only over a narrow arc when the wipers are at the bottom of the windscreen. This signal is fed back to the BCM so that if you switch off the wipers in mid stroke, they don't just stop but instead the BCM makes them carry on until they are at the bottom of the screen and then stop.

I suspect the park switch or its wiring back to the BCM is faulty, so the BCM doesn't "know" that they have got to the bottom of the screen and instead of stopping they just carry on ! The fact that you are seeing 11.5 volts on Pin 5 suggests that the switch isn't doing its job, assuming you measured this with the wipers at the bottom of the screen.

To summarise, the wiper wires are:

Pin 1 Ground Black
Pin 2 +12 Volts Light Blue/Black
Pin 3 Fast/Slow control from BCM White/Black
Pin 4 On/Off control from BCM White/Blue
Pin 5 Park feedback to BCM White/Green

Your next move depends on your skill level. Most folks would swap out the wiper motor. If you think there may be corrosion in the spindle bushes you might decide to replace the whole assembly. Neither of these options are outrageous for cost if you are just paying for parts and supplying your own labour.

The cheaper and more time consuming alternative is to dismantle the wiper motor and fix the park switch, which is simply some brass segments with two springy finger contacts - see pics. Sometimes these don't have enough pressure to cut through the film of grease inside, especially when the motor is cold. You may have to drill out some aluminium rivets and replace them with small screws when reassembling the cover and gasket.

 

[littles]

Thank you for your detailed response, very much appreciated!

A faulty park switch makes sense for the symptoms, I think my next step will be to replace the wiper motor myself. Doesn't look too difficult in the eLearn instructions.

As an aside, I took my voltage readings on the 5 pin connector when it was disconnected from the wiper motor. Based on my understanding of your explanation, the 5 pin connector should be connected to the wiper motor to properly diagnose the faulty park switch. Am I correct in thinking this? If so, how would I go about measuring the voltage when everything is connected?

Thanks

 

[Anthony489]

Hi

The way a garage would do it is to use "Back probing" where a slender sharp metal probe is pushed down the back of the connector to contact the metal pin inside the shell. You might be able to improvise with a large sewing needle or a paper clip.

Here's a guide to motor replacement I posted some years ago:

Ducato X250 Wiper Motor Replacement | FIAT Ducato

The front wipers on my 2009 Ducato based Motorhome would sometimes not start for several seconds, all modes affected. Once going they worked and parked normally. After a few weeks the seconds of waiting had worsened into heart-stopping minutes. Rather dangerous when you have to pull over and...

www.fiatforum.com

 

[littles]

Thank you Anthony.

Will post here when I have it resolved.

 

[acer45]

I have exactly the same problem in a Ducato also from 2007. I tried to swap the wiper motor, but nothing changed. In multiecuscan I have two errors:
B1021 - Windshield wiper relay speed 1
B1022 - Windshield wiper relay speed 2

@littles Did you manage to solve the problem?

 

[littles]

Hi @acer45 , Yes I resolved the issue. The issue was caused by a faulty steering column switch in my case.

The wipers are turned on when the resistance between pins 1 and 4 on the steering column switch drops. In my case, the resistance between the pins when the stalk was in the off position was the same as the resistance it's supposed to be for speed 1, hence why it wouldn't turn off. You can access the pins by removing the plastic trim around the steering column. Measure the resistance and see if it's reading correctly for you in each stalk position.

The resistance between pins 1 and 4 for each wiper position are:
off - 1990 ohms
Intermittent - 690 ohms
Speed 1 - 220 ohms
Speed 2 - 0 ohms

Let me know if I can help further.

 

[acer45]

Thanks @littles for answer!

Exatcly the same problem in my case - a faulty steering column switch. I changed it to used one from junkyard.

Cause of problem I recognized when i unplugged wipers connector under steering column.