General Motors Windshield Wiper Extra Wipe

Q: What’s with the extra wipe after turning off the wipers?

A: Some people consider this an annoyance while others think it’s great. It’s a common "feature" on most GM cars. Although some people claim that their GM car doesn’t do it. There are also aftermarket wiper motors which don’t do it. So where did it come from?

The ultimate wiper trivia might trace this back to an excess inventory of the old kind of intermittent wipers which violated that original patent. Someone had a patent on the infinite-variations intermittent wiper style. The 4th gens have little tick marks with about 10 levels of intermittency. The old kind had an infinite amount of intermittency, rather than a variable resistor with only fixed values possible. GM was one of the first companies to settle with the intermittent wiper patent person. But it also looks like GM changed their method of doing intermittent wipers at about the same time. As for the "extra wipe", it’s just because of the way the RC circuit was set up. There must have been a little glitch when the switch shut off, such that a little extra charge got into the RC circuit and pushed it over the limit right as you turn off the switch. It looks like they fixed this glitch when they changed the style of intermittent wiper control.