i used my system all winter last year
only once had a problem, the car temp said MINUS 4 and it was B4 7 in the morning
my pump had frozen, so now i take the cart out of the car and put it in the garage, jobs a good in
a side note, i decided to clean the doors and lower bit with a mop and sqeegee as i was on site (would save a trip back)
i went to the toilet and filled the bucket up with HOT water, put some GG4 in it, and put it on the window, it froze as soon as it touched the glass
this is the only time i have EVER had a problem, i got home, looked at the pump box, couldnt see anything, had a bite to eat and then started work on it, by that time it has thawed and was working
people have said that HOT water freezes at the same time as cold on glass