J Henderson

My guess is that the wiper linkage will be busted.
Had the same thing happen to me during winter last year, except it was the passenger wiper.
As @johnatg suggests, the wipers were frozen to the screen at the time and they tried to operate automatically when I powered up the car.
The linkage has a ball and socket type setup for the moving parts, (kinda like a human limb joint) and in my case, the passenger side socket had popped out.
I don't think its supposed to separate and reattach voluntarily as I couldn't get it to pop back together again properly. So, my guess is once this happens, a replacement is needed.
As a temporary fix, I used a bunch of zip-ties on the mechanism to keep the ball and socket pressed together. This did the trick, albeit the wipers now made a creaking sound.
That "temporary" fix was over 6 months ago now and is still working fine. But, I reckon I'll be pushing my luck to expect it to last throughout this winter coming up, so thanks to this topic appearing, I’ve just ordered a new one from amayama for approx £92 delivered.
The part number is 85150-53071.

So, I decided to investigate what was causing this, and as suspected, it's the aluminium mirror frame that's corroding.

Thankfully, mine are nowhere near as bad as that image I posted earlier in this topic. 

They're still quite crusty though! I was greeted with a shower of aluminium oxide dust when I split apart the outer shell.

I cleaned the frame up as best I could with some APC and a stiff bristle brush. That got rid of the bulk of the loose debris.

I then masked up the mount/base and brushed on a coat of metal primer.

This is the stuff I used. Whilst that was drying, I cleaned up the two halves of the mirror shell and the puddle light.

Everything put back together, but now with smoked sequential turn signal. These cost a whopping £2.32 from AliExpress so I'm going to be skeptical about their longevity.

I quite like how they look though. The silver/black contrast is pretty much the theme all over my car. Here's the OEM one on the other side for reference.
Unfortunately it started chucking it down before I could repeat the process on the driver's side mirror. I'll have to wait and see if I get a break in the weather tomorrow, to finish the job.
I'm not sure if this process will be enough to help eliminate the streaks, or whether I ought to apply something else, but I figure it should at least help. I'll report my findings.

There will be electronic modules on top of the strut towers if it has AVS.