I was traveling in the mountains w slushy roads at 8,000 feet and temp at 17. went to use my windshield spray and nothing, but heard pump working. had -20 washer fluid in it. 1/2 hour later, it was working off and on. Next morning, 10 degrees in Steamboat Springs, and they worked. IDK? It sucked stopping to put snow on windshied. Its an 2012 RX350.

 

We use fluid for -45 locally. You had ice in the system.

 

In Canada, -20 fluid is what we use only in summer just in case of a cool morning.

 

The altitude was a major factor in how the stuff reacted to the temperature.

As the atmospheric pressure decreases, the boiling point of a liquid decreases since it takes less pressure for the molecules to leave the liquid. So the result is that at high altitude, the boiling point is lower than at sea level. Decreasing pressure also increases the freezing point, only not by very much.

 

Or... The fluid was old as and most of the alcohol evaporated out of it.

 

And maybe it was more diluted than expected. You never know exactly how much remains when adding fluid.

 

The washer reservoir holds over a gallon, It takes a while to empty it. A light comes on the dash when that happens. But keep going because there's more in there. I know because I've done a 'spray' and fill a few times when the weather changes. Now there's all season washer fluid good to -25. So far so good.