Rear washer/ wiper randomly turning on

[Sol]

Try a full BSI reset, it may help. Either follow the procedure in the how to section / B9 sections (at the top in PINK) or pull the glovebox out, then on the BSI (sited behind it) look for a large green link which looks like a fuse, marked [HS - SH] and pull it out. Wait a minute, then re-insert it in the CLIENT position and not the PARK position slot. (If you put it in PARK then the car will no longer do a lot of things, like unlock the doors on remote, operate the interior lights etc.)

That link performs a hard BSI reset (reboot) and things may resolve themselves after that. If not, you could have a faulty Comm2000 module behind the steering wheel (the circuit board which is connected to the stalks and switches.) - that can be changed without programming BUT it must have the same features as your original - so the stereo control and or cruise for example, whether you have auto wipers or lights, must be the same as before.

I don't know about Norway, but here, a dealer will not be keen to take a 10 year old car back due to the rear wiper acting by itself, nor would anyone scrap a car for that - in my opinion.

[saskak]

I think this whole random wash/wipe is due to a faulty rear wash/wipe stalk. Well, not faulty, but from random vibrations it interprets the signal as turn the wash/wipe.

Not the same car, but the com2000 is not that different and the stalks are shared across PSA. My Peugeot 307 had intermittent lights, i.e. they were turning on from time to time on their own. I replaced the whole com2000 (exact same numbers) and that fixed the random headlights, but the rear wash/wipe started acting. It was not there before. I had the original headlights stalk apart and there was one of the metal contacts slightly bent and that was very close to getting a contact, so from a vibration here and there it made the contact.

So, my guess is that it is either a fault somewhere else or the stalk makes a weird contact that gets interpreted by the BSI as put the rear wash/wipe on.
Problem is that these stalks are difficult to take apart and fix the metal wires inside that do the contact.

[blackblingo]

Is there an elegant way to disable the function entirely(only for the rear) while hunting parts? Random liquid sprays and wipers going haywire in the rear is no bueno.

[Sol]

You can unplug the wiper on the tailgate but not the squirter as the front pump has two outlets and does both ends. It's hidden behind the inner wing on the drivers side.

[blackblingo]

They changed the BSM unit, didn't fix it. It happens rarely as of late, or maybe I got used to it. These french cars are strange beasts. What would be the next component to check out?

[saskak]

They changed the BSM unit, didn't fix it. It happens rarely as of late, or maybe I got used to it. These french cars are strange beasts. What would be the next component to check out?

Not too sure what the BSM unit is, but you need the com2000 unit. Either open the stalk, which is to say the least problematic, or replace yours with a second hand unit with the same part number. The problem is that the second hand unit might have the same problem or slightly different problems.

[blackblingo]

BSM module*

will the com2000 swap need reprogramming?

[saskak]

BSM module*

will the com2000 swap need reprogramming?

No need for programming, it is plug & play, as long as it is the same part number as your old one.

[Sol]

This is why it's not easy to disable the rear wash function (unless you fit the screen pump for a van) - the result of pressing buttons on the Com2003 is a stream of exact data bytes to the BSI which it then interprets according to stored tables in its ROM. See below:

   
   

Way more complicated than you think it is (unfortunately).

I assume by BSM you meant the engine bay fusebox (some call it that - PSA call it PSF1) or the BSI computer - in which case if this was swapped out and still not working then the com2003 is the likely problem or the stalks part at least, as @saskak says.

[deejay_xb]

maybe it's a feature
it uses rear wiper and washer if you had not use it for a while, so that the hose will not get blocked
my tractor does this maybe 1-2 times per year