Miter Saw won't start - rounded up the usual suspects to no avail

[lspooz]

Posting here for the collective wisdom from a long time but low-profile member: my four-year old DW706 Compound Miter saw has seen light use in a climate controlled garage but recently acted up:
Over a day or two after cutting the blade took a little longer to stop. Then during a repeated cutting run the saw slowly spun down and stopped, then would not restart. No burning smell nor odd noises, just gave up the ghost. No noise/effect when attempted to start.
I checked power supply and cord, then switch (taken apart, cleaned: voltage was checked and switch operating on-off correctly; reassembled). Brushes removed and replaced with a new set (the old ones WERE rather worn down). Motor parts looked clean and intact.
When new brushes installed the saw started up for 4-5 seconds full speed then same effect: blade stopped turning slowly over a few seconds, then would not restart.
When brushes pulled they had a little soot on the side - cleaning with a soft cloth and mineral spirits helped briefly (blade restarted for perhaps a second), but since then it seems totally dead even with repeated cleanings.
Troubleshooting websites offer multiple videos with little help and great advice including " One another issue which may prevent the miter saw to start off is because the brushes might have worn out. To solve this, you must have the brushes replaced by an authorized professional"

SO, am I overlooking something else easy or is it time to re-read NCWW posts on choosing a miter saw?
Thanks in advance for any advice

 

[Joe Scharle]

I'd begin by ohming the switch. They're cheaply made and I've had to replace them on other tools...mainly routers.

 

[Henry W]

Sorry Larry - can't offer any specifics. You have done what I would have tried.

I did have a similar but different MS account. My trusty PC 10" MS (all metal version, and getting heavier every year!) is one that I bought used 15-20 years ago, can't recall specifically. Never changed the blade at all and it have been consistent and cuts great.
Recently I made a few cuts and it was acting differently. Cuts in walnut were burning, seemed to slow easily in light cuts, took longer for blade to stop.... and I thought maybe this trusty beast is finally getting worn out and sloppy. But first maybe I should check a few things.
First thing I do is go to take off the blade, and discovered it was starting to get loose. Tightened that up and tada... trusty ol' MS was back to normal!

I hope your diagnosis and repair comes to you as clearly (and easily!).

 

[bob vaughan]

Sometimes the brush channel gets a little corrosion or dirt in it and won't let the brushes fully seat against the armature.

 

[JGG]

Rusty/corroded armature considering low use is a good possibility but I’m not sure that is serviceable at home.

 

[Oka]

It is electricity, you have to check in sequence. Check is power getting to the switch, check if switch is working. If that is so, then check and make sure there is no overload/heat breaker/switch (likely not). Then with the motor unplugged you can do a ohm check and continuity check on the motor itself.
Here is a link on how to do it. Elec Motor Testing

Remember, Almost all miter saws are universal motor. The DeWalt is a universal motor.
Universal motors means they can run on either AC or DC.

Hope this helps

 

[bob vaughan]

chasing down a solution to an electrical problem can be frustrating. It can be something as simple as a slightly loose connection somewhere that will test good but won't carry the amps needed to make things run. A cheap cord plug that has most of its strands broken is one I've seen from time to time.

 

[JGG]

I have a DW716 with a similar usage profile so I am following your progress. Please post a follow up if you get it figured out.

 

[junquecol]

My money goes on the switch. Not only does it handle the current upon start, but also when the braking engages. When the B&D Super SawCats came out, we kept an extra switch on the truck on the job site, as the switch was the weak link.

 

[lspooz]

Great advice, will work on it Saturday afternoon if the switch arrives

 

[tvrgeek]

Dust in the contacts for the brake unit. Not unusual. Cheap trigger switches also common.

 

[Henry W]

Ironically my MS just stopped working yesterday too. I had it set up to do a couple of cuts in some trim, had it plugged in to an extension cord and turned on to test power. Motor started for a split second, then stopped. Haven't had a chance to diagnose yet, but will follow advice given on this thread. I suspect the switch as primary culprit.

 

[tvrgeek]

Henry, sounds more like a breaker popped than a bad switch.

 

[Henry W]

Henry, sounds more like a breaker popped than a bad switch.

Thanks.
Other devices on that circuit continued to have power, as far as I could tell. I did not check it on another circuit though, so will do that before I disassemble.

 

[Hmerkle]

Thanks.
Other devices on that circuit continued to have power, as far as I could tell. I did not check it on another circuit though, so will do that before I disassemble.

is there a motor breaker / fuse?
I "acquired" a lathe headstock and the electronics were "blown" since he used a small extension cord - (dirty power)

 

[Henry W]

is there a motor breaker / fuse?
I "acquired" a lathe headstock and the electronics were "blown" since he used a small extension cord - (dirty power)

Don't know - but I did not see one with any external access. I only saw 'ports' for the brushes - at least they were positioned like I would expect for brushes (two identical on opposite sides).

 

[Hmerkle]

Don't know - but I did not see one with any external access. I only saw 'ports' for the brushes - at least they were positioned like I would expect for brushes (two identical on opposite sides).

What brand is it - look-up a manual for it on-line (if you don't have a hard copy...)

 

[Henry W]

It's Hitachi and I think I do have a hard copy, but finding it online is easier that finding my hard copy....
Thanks

 

[Hmerkle]

It's Hitachi and I think I do have a hard copy, but finding it online is easier that finding my hard copy....
Thanks

I looked up "A" Hitachi manual and DO NO see a reset switch nor a fuse, so as with Larry, likely start at the switch...
Also is there a blade brake on yours? (I seem to remember someone having trouble with the blade brake staying engaged... YMMV)

 

[frankc4113]

First of all, I hope I'm not reiterating anything others have stated in this thread. However, having had this issue with my Dewalt miter saw, I researched and followed these directions.
If the saw has a brake, there are 4 electric connections on the switch. Using an ohmmeter, place the 2 leads on the 2 black wires controlling the start/stop function with the switch off. Turn the switch on and there should be a change in the ohms if the switch is good at that point. Then place the 2 leads from the ohmmeter to the other 2 sides of the switch that controls the brake. Turning the saw switch "on", there should should be no change in the ohms. Then turn the saw switch "off" and there should be a change in the ohms that indicates the brake is working properly and the switch is good. If all those tests are okay, the switch is good.
Of course, all this has to be done with the saw unplugged.
I hope I've explained this properly. The issue with my saw was resolved by taking the motor out and blowing everything inside and out with compressed air. When I put it together, the saw worked fine. I'm still not clear how this all happened. Maybe I inadvertently fixed or tightened a connection but as long as it works, all is Okay. On the other hand, part of me was hoping it wouldn't work so I could buy the new Milwaukee saw that has a 5 year warranty. Oh well, the Milwaukee was too expensive anyway.