How to use Wifi re-installation code? I've a Samsung Galaxy Ace but my Wifi is always not in range. 

Google Helps state:


  Use WiFi driver re-installation Code *#*#526#*#*...Reinstall the
  firmware for Wifi. Try it on other Routers as well  this is a common
  problem with Androids. as i see (seen in lot of forums people
  discussing Wifi problem of Androids) My cousin bought the same Handset
  and he is having same problem. If it doesn't help show it to your
  vendor from where you have brought it


How do I use the WiFi driver re-installation Code *#*#526#*#* ?
These are called dialer codes, so naturally try typing it into your Dialer as if it were a phone number.  I just did it on my Vibrant and got this:

WlanTest Engineering Mode
Status...
Unloading Normal Driver and Loading Mfg Driver

Driver loading successful