how do I repair washer fluid assembly neither front or rear works,
It may need a washer fluid motor, which I am not familiar with Volvo, But is usually attached to the washer bottle. Sometimes these go bad and need replaced. Also if the motor is good, there may be a damaged hose somewhere, which most likely just will need replacement as well.
On my 1983 Volvo 245 I found a wiper/washer switch which is the stalk on the right side of the steering wheel at a pick and pull wrecking yard and installed it in place of my original one and now my washer squirters work front and rear.
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