I carefully scraped off the excess silicone last night and secured the mirror to the plastic mounting tab.
Then I squared myself up in the driver's seat and reached up and adjusted the mirror - and it came off in my hand. The silicone stuck to the glass just fine - but not to the plastic mount. It took a while to scrape the silicone off the windscreen - it was stuck very well! There was NO silicone stuck to the plastic mount. Keep in mind that the little tube of silicone (vinegar smelling type) came with the mounting kit.
I have read a fair bit (web) on these failures recently so my three choices are:
- Rough up the back of the plastic mounting tab with sandpaper and try the silicone again (I have enough left to try once more).
- Use the metal mounting tab that came with the mirror although I'm concerned that the silicone is the corrosive type.
- Go and get another adhesive product for mounting mirrors.
BTW - The silicone oozed out the sides of the mount - none of it went up those square holes in the mount which are obviously designed to "key" the glue.