I recently bought my first Garmin GPS, Nuvi 2598, from Costco. In general, I like lit but the most annoying problem is that the brightness kept dropping to 20%. I googled and tries a number of different solutions, including change time settings to auto, uncheck demo mode, etc. After many tries (including returning a GPS back to Costco), I now have my guess and solution to this problem that I want to share with ppl who are still experiencing the same issue.
Guess (skip if you are only interested in a solution):
Even though there is only one setting option for brightness, internally there are a number of brightness parameters saved within a Garmin gps depending on the other settings. These settings include color mode (4 options: manual day, manual night, auto day and auto night), Current time (4 options: auto day, auto night, manual day and manual night) and power supply (2 options: with power plugged in and without power). There are up to 4*4*2=32 different combinations (some of them may not feasible, e.g. auto day in color mode and auto night in current time setting can't be set at the same time). My guess is that developers/Garmin want to provide more flexible settings for users (and save battery) but fail to provide clear guidance. In short, my point is that there are many brightness parameters you need to change. The default settings for most of them are 20%, which is why the gps suddenly changes to 20% of brightness whenever color mode changes and/or power setting changes. Some default settings may already be changed to different values by Garmin, which is why some ppl claimed to solve this problem by changing current time setting to auto.
Solution:
1. Set color mode into auto
2. Set current time into auto
3. Set the brightness during day time hours twice:
3.1 firstly, plug your gps into your car power outlet and set your preferred brightness during day time, e.g. 90%
3.2 secondly, unplug your gps and set your preferred brightness again, e.g. 90%
4. Set the brightness during night time hours twice:
4.1 firstly, plug your gps into your car power outlet and set your preferred brightness during night time, e.g. 20%
4.2 secondly, unplug your gps and set your preferred brightness again, e.g. 20%
You are all set!
Let me know if that works for you.
