Dewalt dc618 lights yellow but doesnt run - Dewalt DC616kn 18 - volt 16 - gauge straight finish nailer

Trigger may be stuck try a little singer oil or sewing machine oil only a few drops should do it... trigger switch may not be working properly either

https://www.weeklytools.com/dewalt-angle-grinder-buying-guide/
When it comes to Angle Grinder, the name of the Dewalt tools maker comes first. We will look at the basic parts and functions of a grinder before purchasing a machine. Then let's see the details without delay.

If the motor runs and stays running when you depress the nose then the problem is in either the trigger switch or the solenoid.
If the motor runs for a moment and shuts off with the light blinking I would check your battery. These are very temper mental with voltage, and even if your battery just came off the charger & might work in a drill, it may not have 18v to supply the electronics.
Please note - these are not easy tools to work on, I would recommend bringing it to a qualified repair shop near you.

Continuous flashing indicates low battery charge or poor battery connection. If lights flash 4 or 5 times indicates possible control module fault.

firstly its always better to change both of the bands even if one is broken this always keeps the drive trim.all seems well clean all the contacts ie battery and gun (do not use any cleaning products this will cause grease)just wipe clean with paper towel.

The link below is where you can download the owners manual. The link is on that page near the top right hand side under the area marked downloads. Page 5 will show you were the switch is located that switches the tool from sequential fire to bump fire.

DeWalt DC618 parts and operations manuals

You have to take the front part of the case off, and you will see the problem. Either the drive belt is broken or the rubber band like springs have broken. Happened to both of mine after about 2 years of use. I ordered the parts through Dewalt and they have some nice diagrams showing the locations and how things go together. Not too hard to do

Check the battey then take it out and check the driving rod. On the front of the gun, flip the latch and make sure it is pushed all the way back.
make sure you have nail, of course. put the battery back in. If al that does not work, have it services at a dewalt service center.

just goto:
http://www.retrevo.com/search/v2/jsp/mytrevo/myTrevo.jsp?page=man

download the support manual. You should be on your way

problem solved.whoever had used the tool must have hit something hard because the drive pin had been pushed back just enough to stop it from cycling.