Confused rear washer on my C5

[Sid_the_Squid]

Hi all,
My new (to me) C5 has developed a strange quirk, using the front windscreen washer will active the rear washer, and vice versa, its most distracting to try and wash the rear screen and have the front washers kick in. Not a major issue at all, but something I'd like to address.

As this is a multiplex (correct term?) car where does one start looking for this fault?

Thanks all

[Citroenmad]

I think your quite right to pinpoint it to the multiplexing, often switches start operating different functions when the unit fails. However, it might only fail in that area, the rest of the functions might remain unchanged.

I had one which, when i indicated right, would indicate three times them turn on the headlamps. It was he comms2000 unit which was at fault, i replaced that with new and its been fine since.

Its not a hugely common fault, thinking how many cars are multiplexed, relatively few owners experience problems with the comms unit.

Saying that, it might well be something more simple.

Something you could try is activating the washers with the wipers turned on, as this should make the unit send a different signal. It worked for me with the problem mine had, with the headlamps manually turned on, the indicators worked perfectly.

[myglaren]

Swap the output pipes on the pump.

[Sid_the_Squid]

I think I explained that badly, what I mean is both washers come on simultaneously, when your trying to activate either the front or back washers.

[myglaren]

That is odd as the way they work is the pump motor is bidirectional and there are a couple of flapper valves that help to direct the flow.
Depending on the direction of rotation the fluid should flow through one pipe only.
Mine only goes to the front washers, the rear hasn't worked for a couple of years. Keep meaning to fix it but never do.

[JamesQB]

This is a fairly common problem on the Megane that uses a bidirectional motor and valves. Mine currently does the same thing: washing both front and back regardless of which I activate. Apparently the valves are the trouble, allowing flow through both at the same time.

Solution is new pump. I can get an aftermarket for £7 but haven't bothered yet.

[Citroenmad]

When both washers activate, do both of the front and rear wipers work too?

If it was a faulty pump valve that shouldn't turn on both front and rear wipers, only the washer. If its comms related id expect both wipers to functions, rather than just the washers.

[Sid_the_Squid]

Just the washers have the simultaneous issue, the wipers work quite happily on an independent basis.

[mooseshaver]

My C5 did this and it needed a repalcement pump.
Mine would wash the front ones ant the same time as the back, which was fun on motorways becasue you have to suddenly use the wipers so you can see.
Its common on lots of cars my brother tells me.

[Paul-R]

Its common on lots of cars my brother tells me.

Which means they all use the same crappy design.

My C5 didn't do the "two for the price of one" but instead would only spray the rear window. I took the pump off a few times to wash it through but in the end had to change it for one from a scrappy.

Out of interest I dismantled the pump and found a strange moving shuttle valve inside. This seems to be prone to jamming if there is debris in the water so make sure that the inside of the washer bottle is cleaned out before fitting another one.

I would have been a good idea if Citroen had fitted a filter into the filler neck like VW do. When I saw one on my daughter's Golf I though it was an excellent idea.

[dnsey]

I haven't used it for years, but the Citroen-branded screenwash (Stop-Clair?) used to form a gritty precipitate with some types of water, which would jam the pump and block the jets.

[myglaren]

I haven't used it for years, but the Citroën-branded screenwash (Stop-Clair?) used to form a gritty precipitate with some types of water, which would jam the pump and block the jets.

And Citroen say to only use their screenwash to avoid such problems