It's been about -20°C here for a while now and I foolishly topped up with -15°C screenwash just before the cold spell came. Obviously, the fluid in the tank has turned to slush. I'm not too worried about the pumps and hoses because it doesn't freeze outright at these temps, it just becomes too viscous.

 

Anyway, I noticed that the high pressure pump does run, but the sprayer jets in the front bumper don't pop up like they should. I had always thought that they were operated by an electric motor, but apparently not. My next guess is that they're operated by pressure from the pump and then pulled back in by a spring, but it's just an educated guess. 

 

Does anyone have an idea of how these actually work? By total coincidence, all my previous cars have had actual mechanical headlight wipers. This is my first car with (useless) high pressure sprayers. 

I think it's just water pressure and spring loaded to return

Yes it's the pump pressure that lifts them

If the slushy screen wash isn't flowing they won't pop out as previously mentioned.

They could well be frozen to the bodywork and cannot freely move, try some deicer around them.

I think the jets are heated but the mechanism isn't so can freeze solid.

I thought mine were frozen in the weather here in the french alps I'd put -36 screen wash in but then remembered they don't work unless the headlights are on! 

I think there is a seperate pump for the headlight washers. If the jets have been frozen to the bumper it can blow the fuse , I can't remember what fuse number (maybe 20) but it's worth a look.

Yes, the pump is obviously separate since washing headlights needs a lot more flow and pressure. 

 

And yes, everything started working normally again as soon as it got a bit warmer the other day.  

 

I guess I'll have to use up the current tank of fluid now so I can top up with proper -40C stuff again. Thanks for the replies!