Bought 2 no BTD142 impact drivers from Makita USA got drop down transformer they just start to charge then tones for broken battery are heard and stop charging, transformer new, batteries new have i done something wrong.

the light is normally activates by the trigger, so either the switch has gone faulty or the wires running to bulb are contacting.
press the helpful button and check link below

Makita BTD142 Trigger Switch Replacement

Go to the Makita home page, http://www.makitatools.com/en-us/Modules/Home/Default.aspx, and put your model number in the search box to find their page on your tool. On the left side of the page will be the parts breakdown and owner's manual for view or download if they are still available.

Likely to be weak battery due to end of life. Test battery voltage with meter right after charge , then again after use then stop. If voltage changes /drops, battery is worn out. If battery has full charge, check the condition of the battery contacts within the driver. Pull out the battery and look inside. The contacts should look bright and shiney. If dark, may need to replace them, but suspect that the switch is also bad. Good luck.

The battery itself has a deep discharge protection .
Or the electronic or the battery its a new
phenomenon where you can have bought electronica and a triggerswitch and you have measured the electric field on 0.3 ohm on both 2x3 coils and the battery measured on maybe 15 Volt and it do not give nothing yes the lamps burned , but there was not an charger in my case delivered so i am also waiting for this problem by a Makita Jigsaw because a colleague has allready a electronic circuit and switch ordered and tried with that battery and an other battery but no life at all, so a new battery should may be working. or a broken or new damaged electronic part was delivered. that brushless tools are a young technical thing, many brands have.
the teething problems out, by the switches and the power mosnfets(panasonic) Makita is new for me this comparable problem a have also have yesterday.
next week i know more about a possible solution.
Makita BTD144 Lithium Ion Impact Driver Brushless Motor Parts

could be the anvil stuck on the hammer mechanism, try locking a bit in a vise and impacting. also could be wear on the edges allowing the 2 to slide past each other

on my charger (DC18SC) alternating red and green dual flashes mean a defective battery.
http://ubermanuals.com/product/makita-dc18sc-8866 also same for the DC24SA

the makita impact drivers are picky about the bit that you use. if you use a single sided bit you have to make sure the distance between the channel and the end is 9mm (3/8) and if you're using a double sided bit you have to make sure the distance from tip to channel is 12mm (15/32)

try using a 1/4" wrench on the bit in reverse while pulling the collar back. if that doesnt work, tap the tip of the bit with a hammer with the collar pulled back

What has happened is the hex part of the bit has twisted slightly making it hard to remove. What I would do if you are comfortable with partial disassembly is remove the quick release mechanish. There is a split ring that comes off first and then a washer and spring, next remove the outer collar and SMALL steel ball from side of chuck. I take a pick (dental tool) and push up or try and twist the stuck bit. Sometimes it takes while but usually this works. Let me know if I can try and help further.

Most likely, but unless the transformer blew, which is somewhat unlikely, a good repair shop should be able to fix it. Basically the charger unit is a transformer, some diodes to convert ac into dc, and some sensing circuitry to tell you when the battery is done charging. Diodes and sensing cisrcuitry are commonly available parts and not expensive. Transformers are expensive. Even if you get it repaired youll still need an adaptor to convert from the mains 240 to the 120 that the charger wants to see. Get one with a high enough wattage for the charger. Wattage is printed on charger base.

Also bought the new ion kit 3.0 didn't have it for a full month battiers gave me a problem. I bought one and didn't use it for a full week and did the same thing!!