I have a garmin gpsmap 176 that no longer displays anything on the screen when you power it up. The backlight still works but nothing displays. I have used it on boats, trucks, cars and motorcycles. Not long ago while using on my motorcycle, I noticed horiziontal black lines flickering across the screen. Now it appears the screen has gone out.

Consult page 11 of the owner's manual
http://static.garmincdn.com/pumac/3291_OwnersManual.pdf , and follow the instructions. Pressing the power key repeatedly cycles between maximum backlight, minimum backlight and manual settings.
If this does not work, contact Garmin support

http://www.garmin.com/support

This link will work for you wherever in the world you live.
Please allow time for them to reply. The support team may be in a different time zone :)

Backlights are part of the LCD display and consist of LED's. You may have to replace the entire LCD display or find another display that is cracked but has a working backlight. In most cases, you can swap backlights. There may be some soldering involved.

Did I understand this right, you do know how to replace the backlight, but you cannot locate it inside the unit ? Try to look here: http://goo.gl/6hCS

Look at these places to have it repaired

http://www.megagps.com/techservicestuneup.aspx?gclid=CKurjNiuhqoCFQFZ7Aod8Sbuzg

http://satnavrepairservice.com/repair-satnav/garmin-repair/13.html

http://www.pdasmart.com/gps_repair_parts.htm

Can you reset it?

The GPS does not have a line of sight to the satellites. Reposition the GPS so that it can receive the satellites signal.

Backlight problem: Remove the display, remove the light tube from behind the LCD. Buy a led panel from Ebay for around $5 and install it behind the LCD under the drfusing layers. Run the wires out to a 12 VDC source and there you have it.

try adjusting backlight controls, also on a bright day try it shaded

i have a 1 gig 182c works fine

The power switch usually allows you to adjust the backlight with a short tap there should be a scroll bar, use the four way toggle up to increase the back light.