Is your M12 tool blinking a Christmas light pattern at you sometimes when you try to use it? I may just have the solution for you.
I saw a post on the Garage Journal where someone was having an issue with their M12 Fuel Impact where it would blink at them when they pulled the trigger. The Milwaukee tools use blink codes to indicate that the tool has identified a condition in which it should not run.
Some of the possibilities are when the battery is too low, when the battery is overheating, or when the tool has stalled. After investigating the contacts on my tool and battery a little bit I discovered that if the tool cannot read the temperature sensor in the battery, it will not run.
By putting tape over the terminal I can simulate a condition where either the tool or battery contact are corroded and not making a good connection.
If you are intermittently getting this issue, it may be a good idea to check out the contacts and clean them if necessary. It is a very cheap and quick thing to try to fix an expensive tool. You’ve really got nothing to lose.