Repairing a broken mains hammer drill

[mangocrazy]

I have a Hitachi corded hammer dril (DH24PX SDS Plus 240v) that has served me well for quite a few years, but which has recently become erratic in operation. It's developed an annoying intermittent fault - some times it works, other times it doesn't. I've checked the fuse and gone as far as replacing the moulded plug to ensure that wasn't the problem. What should I be checking first, and are there any obvious potential failure points to eliminate? I've opened up the section at the back by the trigger, and there appears to be adequate brush material. Is the trigger itself liable to be a point of failure?

All suggestions appreciated...

 

[JEZGUZ]

I'd guess on a fault with the cable. Use a multi meter to check for continuity while jiggling the cable, it should show up a fault if there is a break in the wires.

 

[eddie49]

I'd guess on a fault with the cable. Use a multi meter to check for continuity while jiggling the cable, it should show up a fault if there is a break in the wires.

I would agree, and if there is a break in the cable, it is likely to be just where the mains cable enters the tool, at the bottom of the pistol grip handle.

 

[Memmeddu]

I would proceed this way
Check the power cord looking for soft points which indicates a broken wire generally at the ends ,but might also be broken in another point, most likely it's broken at the plug or at the closest point to the handle.
Carbon brushes can also be worn or damaged , another thing to check is the switch.
If all those are ok ,it can be the clockwise/reverse commutator, can happen that it doesn't set properly in position burning the contacts causing malfunctions.
It again everything is fine we can bet on a faulty armature

 

[dobbslc]

Take the cable out of the drill and with a pair of pliers pull on the cores. Oftenr one will come out about 3" long.
Do the same at the plug end.

 

[cheb]

I'd be latching the tool switch on and wiggling the cable to see if the tool falters. If not then some switch cleaner into the switch and press the switch on and off for a while.

 

[Agroshield]

Cable would be my first place to look too. Switch second. Memmeddu's point about the forward/reverse part is well made - it could be dirty or in a borderline false neutral position.

Carefully remove the switch and existing cable and wire a cable directly to the switch output, so you control it by switching on or off at the mains socket in the wall (or foot switch if you are posh). If you cannot make the fault reappear, the parts you have removed are the source of the problem.

 

[mangocrazy]

Thanks for replies, I'll check those out later today and report back.

 

[brightspark]

if the drills apart just shorten the lead 3 inch and pull the cores as in post 6

 

[Blue Chips]

I have a Hitachi corded hammer dril (DH24PX SDS Plus 240v) that has served me well for quite a few years, but which has recently become erratic in operation. It's developed an annoying intermittent fault - some times it works, other times it doesn't.

I had the same symptoms with a Makita. Turned out it was the switch (trigger).

 

[mangocrazy]

As far as I can see, it's most likely to be the cord where it enters the drill. I held the trigger down and moved the rubber strain relief upwards and it burst into life. Let it drop to 'normal' position and it stopped. Repeated this a few times with same result. So I'll order some new 2 core mains lead (but longer than the rather stingy amount supplied as standard), fit that and while I'm at it clean the trigger out with contact cleaner and replace the brushes for good measure.

 

[KemppiFrog]

My hammer drill has quite a short cable, because it has failed several times where it enters the handle. Rest of drill (Einhalle) has taken a lot of stick over 20 plus years, but still works fine.
Beware of too long a cable, two metres is about right.

 

[Blue Chips]

As far as I can see, it's most likely to be the cord where it enters the drill. I held the trigger down and moved the rubber strain relief upwards and it burst into life. Let it drop to 'normal' position and it stopped. Repeated this a few times with same result.

Sounds like the likely culprit.

 

[dobbslc]

and while I'm at it clean the trigger out with contact cleaner and replace the brushes for good measure.

I'd be weary of doing that!
You might wash crap into the switch and it'll play up after.
If it ain't broke don't try to fix it!
Just replace the cable.

 

[KemppiFrog]

Just a comment..The title of this thread was a broken drill, rather than a mulfunctioning one. Reality is, getting parts for drills , or other mech stuff, usually make buying new a better bet. At least you get a warranty with new.

 

[brightspark]

Just a comment..The title of this thread was a broken drill, rather than a mulfunctioning one. Reality is, getting parts for drills , or other mech stuff, usually make buying new a better bet. At least you get a warranty with new.

a switch a chuck carbon brushes the odd bearing and flex anything else is probably not worth doing

 

[mangocrazy]

Replaced the cable today with new and it seems to have fixed the problem. The biggest bother was getting all the wires and trigger in the correct place(s) so I could refit the cover - there isn't any spare space in there. As a result the lock button is limiting the depth of trigger press when in reverse and thereby the speed, but is fine in forward, so I'm happy to leave it like that. I can't remember the last time I used a hammer drill in reverse...

 

[cheb]

Most of the hammer drills I've used haven't gone as fast in reverse. Mostly found out by accident by knocking the reversing lever than wanting them to run in reverse.