Strange wiper issues

[big jim]

Hello I am the proud owner of a 1.6 V reg V40. It was bought as a urgent replacement when out V70 tdi got a bit sick.

I do like the car but it has a rather strange issue with the wipers...

There is no intermittent, sometimes they park correctly, sometimes they don't and every time I put in it reverse the rear wiper activates.

Now I am an ex-mechanic so I do know my way around a modern car and initially my thoughts were either a blown fuse, the switch or the contacts in the motor were up the spout, but when I noticed the rear wiper going with the switch off. I did wonder if this is CEM related.

Before I order a CEM from a scappy does anyone have any other ideas about what it could be?

[steveo59]

Hi Jim,
A couple of months ago I replaced the wiper motor on my other car, then the wipers would not park quite right and when I turned on ignition even with wipers switched off they would always twitch. It turned out that when I had tightened the nut securing the wiper linkage to the motor spindle the linkage had been past the end of it's travel and was preventing the motor from completing its cycle. So when the ignition was switched on it then went into park mode,hence the twitching. For your rear wiper to activate when you put the car in reverse, you have to have your front wipers on. Although the wiper stalk may be off, the front wiper motor may be just completing its cycle.

[bobthecabbage]

It does sound like it could be an issue with the stalk switch.

I can't remember if you can stop the wipers parking by catching the switch half way between positions? If you can, this might be your problem.

The wipers should park themselves without any intervention as long as they have power. There are metal contact tracks on a plastic cog that provide the parking function.

On intermittent a pulse is sent to the wipers which is long enough to activate the self parking function but shorter than a full wipe cycle.

This can catch people out when testing as if there is power and you trigger the cycle, it is going to go to completion even if it involves twisting and scraping of metal and crushing of fingers!

So it is possible that if you have a weak motor and dirty contacts on your self park mechanism, this is your problem.

Not fully understanding how the stalk switch works though, it could be that the problem starts here. If the wipers require a power signal from here to operate, even when the stalk is in the off position (for the park function), that could explain it.

The rear wiper operating every time you hit reverse suggests that the CEM is receiving a signal indicating that the front wipers are on and activating the rear wiper as it is supposed to.

In that case it sounds like the CEM is okay and I would look at the stalk first, followed by the wiper self park and motor, then the CEM.

It maybe that you can strip the stalk down and clean the contact track or swap it out with a known good one.

[happy diver]

I pulled a CEM from a V40 to cure my wiper parking issues to great success
however I was then faced with a non operable rear wiper, because the CEM
originally came from an S40 and hadn't been programmed for a rear wiper.

[steveo59]

Hi,
Glad you've got it partly sorted, at least you know how to sort it properly.

[happy diver]

yeah gatos programmed one and sent to me.

actually I could have flown to Barking mad and picked it up myself
for what Vulva Australia wanted to charge