To troubleshoot start at the wipers and disconnect the hoses and run the washers - if no water comes out, follow the hose to the next connection and unplug the hose there - repeat. keep going, back to the pump if necessary.

There may be a filter in the line, and a check valve - I had the check valve on one of our 740s turn to goo - perhaps from strong washer fluid.

If a check valve is bad, pop it open - there should be a small spring and a bit of thin rubber, DON'T lose the spring!

You can use a piece of dishwashing glove to replace the rubber - the piece is so small, your wife won't even notice.

On our '96 855R one of my headlight washer wipers stopped working - so I blocked the hoses, removed the wiper blades and put red wire nuts, filled with grease, on the threaded shafts.

After a couple of years I checked the shafts and their threads were undamaged and free of rust - still good for the next guy to fix them if he wished.

We had Isabel for 11 years and I still miss her, sob!

No secret button. The headlights have to be on, the wipers have to be on, and the stalk pulled to wash the windows. Hold the window washer stalk to soak the window and the headlights should get sprayed at the same time.

Two pump motors, one for the front, the other is for the rear window.


--
Keeping it running is better than buying new

I don't know anyone who bothers with headlight washers, discontinued by Volvo because they're useless.
I have them. Don't know if they work or care.