Trigger assembly - Kowa TSN-663

Are you mechanically inclined??? This is a little involved to do. First UNPLUG tool and remove the back section/trigger, there are about 6 screws holding the assembly to the back of the tool. REMOVE as an assembly. SQUEEZE trigger and PLUG into electrical outlet, while holding trigger unplug and reassemble, try this if light still on plug assembly in squeeze trigger and while holding the trigger unplug and retry. One if these should take care of resetting the light. If not the only other way is to send it to HILTI and have them reset it. Let me know if you still need more assistance and results.

I had a similar problem with one of my nail guns. What I found was a small rubber o-ring in the trigger mechanism had split. Once I replaced this the problem was corrected and the unit functioned fine.

You could replace the whole trigger assembly for about $35. But if you remove the assemble and replace the split-ring this would only cost a couple of bucks at most.

Trigger assembly shown below. ereplacementparts.com is one possible source for the trigger assembly others can be found on the Internet.

The safety foot assembly pushes up on inner trigger lever which in turn pushes on the trigger valve. If the trigger valve firing pin is slightly shorter than the old trigger valve, or the inner lever is worn from use, the inner lever will not push the trigger pin all the way in. Examine the trigger and the roll pin that holds the trigger for wear and check that the safety is pushing up on the inner lever. If the trigger is worn replace or repair with metal type epoxy filling in worn spots and use a new roll pin.

you need a trigger assembly it sounds like/ to remove you will find 3 roll pins, unplug the air supply and remove all the roll pins in the trigger/switch and then the trigger valve ssembly is easily removed BUT follow closely, after removing the roll pins remove the trigger and then holding a rag under the trigger assembly pull back on the collar to release the bit. clean with chemicals and try ing to find that special commodity.
Dave Ford

See the link below for a parts breakdown of the gun. Usually this problem is a defective trigger assembly and requires that the trigger be replaced. You can also check the Orings. If there is an air leak this can also occur.

Dan

Link: http://www.fixya.com/support/r5812776-bostitch_nailgun_dis_assembly_assembly

there is a split o ring on the trigger assembly that needs replaced or the whole trigger valve assembly needs replaced.

follow closely, do you have a new trigger assembly because the problem is with one o ring commonly referred as the purple o ring in the kits? either way the procedure to remove the trigger is first knock out the roll pin for the trigger latch and then the 2 roll pins for the trigger assembly. next get a shop rag or equivelant and place under the now exposed trigger assembly and then while holding the collar on the air chuck plug into tool and hold rag tight and trigger will "pop" out pull the chuck away and remove the 2 pins to disassemble the assembly or install in reverse order lubricating the o rings first. Let me know if you have any questions or problems.

The part number for the switch is 152274-19 . Dewalt doesn't sell the individual parts for the trigger assembly. It really depends on the manufacturer of the trigger at the time of production. You should be able to locate a company name on the side of the trigger switch assembly. It may be Marquardt. I am unaware of any way to order individual parts for these type switches. If you find a source please post.

You will need to remove the trigger before driving out the roll pin. After you remove the trigger and roll pin, place a rag over the trigger, remove your hand from the area, and briefly hook up your air line. (Clean your soiled pants after this part) You will hear a loud pop and the trigger assembly is going to come out quickly. If you are not prepared for this it will scare the **** out of you. Then once you have the trigger assembly out you can push the two retaining pins on the assembly out and remove the inner workings of the trigger. One note of caution. The ring you are trying to replace is a hard half moon looking ring that Bostitch doesn''t sell separately. You may see it in pieces when you take this assembly apart, or you may not. Sometimes it crumbles and comes out of the trigger exhaust. You can try to match up an oring to sit in there, but from experience it is much easier and less costly to just order the whole trigger valve. Hope this helps.

There is an oring that is probably broke in half, It is referred to as a purple o ring. You can buy the whole trigger assembly but I think that just replacing the one will get you going. Let me know and I will try and help more