Rear Wiper on 2000 XLT only works when cold outside

[TekMan05]

Pretty self explanatory. I've noticed this for the past year but never got around to tackling this issue. Last winter and now this winter when my truck sits outside(normally garaged) the rear wiper which normally hasn't worked consistently for a few years works almost always when exposed to weather around freezing or colder. But once it gets above 40 becomes inoperable. So this has to be some kind of weird electrical glitch that I'm guessing. Anyone else have this problem?

 

[SoNic67]

It might be the motor. Although usually is the other way around... Fail on cold.

When is warm out, I would take the internal cover off the rear door and check for voltage while wiper is activated.

 

[koda2000]

Electronics will typically fail when cold. As you experience the reverse (just a guess) I wonder if the shaft is dirty/corroded and seizing in the black plastic collar or perhaps the housing bushing. Maybe when it's cold out it's just enough to contract the metal slightly allowing the shaft to rotate...?