Peugeot 407 washer

If it's not the jets needing adjusting , are you getting full pressure ? If not ,may be weak pump or partial blockage in washer bottle possibly with any filter fitted on pump assembly .

ok,i1ll check whats the best way to try pump pressure

Normally I would just pull a hose off and check flow at jets , Sometime emptying the washer bottle and putting hot water in can clear sludge / soap build up if causing restriction but if easily removed , a lot better for checking or cleaning .

Have you had a look at this similar problem:

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The 407 has a non return valve for each washer and these can clog and give you the same problem.

There's a little tool that might help called a "screen wash jet tool".
Ebay has them for less than a fiver.
it's basically a small diameter hardened steel needle.
yah poke it in the jet and wiggle it around until it flows better.
Usually fixes it but the pipe can have blockages too.
This is why the fluid bottle has a filter in the neck,
well new they do,
people tend to remove this filter so all kinds of crap can get into the res.
Does yours have a filter?