Magellan Roadmate 1470 brightness problems

I updated the software to 3.11 on a Magellan Roadmate 1470, since the upgrade my display setting are turned all the way up on the GPS, display hard to read in daylight, before software upgrade, the display had no problems, Magellan said to send the product in for repair and is out of warranty. On the GPS there's a brightness.dat file, open it with Windows Notepad, change all settings to a higher numbers, no changes in display brightness, Is there a different file that needs to be modified?

I had this same problem before on my Magellan Roadmate 1412 after an update, made changes to this brightness.dat file and now my Magellan Roadmate 1412 works perfect in daylight hours by changing the brightnss settings in the brightness.dat file.

Here's what the file looks like on the Magellan Roadmate 1470 without changes.

NoDimming=20,40,70,110,160,210,250
Dimming=15,20,40,70,110,160,210