20 Most Recent Hitachi Koki Usa WH18DL Lithium Ion Cordless Impact Driver 18 Volt - Page 2 Questions & Answers

try this link... How do release the bit from my Hitachi cordless drill Google Search

faltering on a slide contact on electric field or switch, but in most cases dirth (dust) in carbonbrushes can be hanging somewhat in one or both brushholders. Or a problem in the trigger switch itself dust and dirth have almost the highest priority in case of faltering by clamping carbon brushes.

probably not older chargers were made for ni-cad batteries and now they are li- ion batteries which require a different charger to distinguish the difference , most manufacturers changed the battery pack design talk with a battery retailer or a good tool shop or appliance repair shop

check the wiring connections to the for/rev switch

voltmeter measure on switch ? 1 of the 4 electric field contacts is broken , or carbon brush has an activated autostop if its to short.

the screw at the base of the fully opened chuck is a left hand thread it may be a slot but normally they are philips head or hex head undo that screw by turning as if doing it up once it is out , hold the shaft and by placing something across the now partially open jaws a quick hit on that object with a hammer will loosen the chuck off the shaft you can place a allen key in the jaws and close them up and use that as an object to hit

Ether the battery is shot or the charger, Did you try charging a different battery?

Need to know the model you have. The larger Hitachi hammers have external brush caps (usually under a metal plate or metal end cover)

Sounds like a battery problem. Try getting a new or better yet a rebuilt battery for it and see if the speed doesn't come back. Your battery maybe worm out and unable to give the same power it did when it was new.