Malfunctioning router question

**Chris in MS** · 09-17-2005, 11:49 AM

Hi guys,

A question for those electrically-inclined:

I have a 2-year old Bosch variable speed router. I haven’t used it in several months and keep it unplugged. Plugged it in this morning, turned it on, and nothing--completely dead (yes, I checked the wall socket). I disassembled it and with a voltmeter and checked the cord, on/off switch, and the variable speed module. I didn’t detect any open circuits in these components. Any ideas on what to do/what might be wrong?

Thanks,

Chris

**rrich** · 09-17-2005, 04:37 PM

Well... If I had to guess... I don't think that I could. Well, maybe, a WAG, brushes?

Assuming that you are getting voltage through the o/o switch, what is the speed controller putting out? Is the SC putting out enough amps to run the motor? Or are you just reading a voltage from a high impedance source?

Just too many unanswered questions for me to make an intelligent guess.

**Chris in MS** · 09-18-2005, 03:28 PM

>Well... If I had to guess... I don't think that I could.
>Well, maybe, a WAG, brushes?
>
>Assuming that you are getting voltage through the o/o
>switch, what is the speed controller putting out? Is the SC
>putting out enough amps to run the motor? Or are you just
>reading a voltage from a high impedance source?

Thanks, Rich.

I appreciate your help.

I know very little about electrical components, so please forgive me for asking some basic questions. To check the actual current through the SC, would I have to plug in the router (and turn it on), and then with the ammeter, measure at two points in one only lead to the SC? That is, I'm not measuing across two SC leads as if I were going to test for SC circuit continuity, is this right?

**rrich** · 09-18-2005, 05:34 PM

Chris,
Actually, you could, but I wouldn't. In effect, what you want to do is measure the voltage from the output of the SC and the other side of the AC line. The theory is that if the SC is putting out enough current to run the motor you should see 115-120 Volts when you run the motor. If see the voltage and then it drops to near zero then the SC is not putting out the current. It's my understanding that SC in routers employ a clipped sine wave method of speed control so regardless of speed setting, you should measure something close to line voltage on the output of the SC.

All of this has led me to another thought. Is the speed control switch functional? You may want to try squirting some contact cleaner into the switch. (Usually available from Radio Shack.)

Here's what bothers me about this whole thing. You used the router, put it on the shelf, a day or two later the router is taken off the shelf and it fails. It's just illogical. If you really want to go out on a limb, maybe, just maybe, heat caused a circuit board to crack. Again, not likely and most illogical. What is the possibility that the router was knocked off the shelf and bounced on the floor? What is the possibility that your router was swapped with one that wasn't working while sitting the shelf?

There is another thing that you can try. With the router unplugged, move the shaft about 1/16 of a turn. Plug the router back in and try to run the router. If the router doesn't start try this 8 or 10 times, turning the shaft 1/16 of a turn each time. If the router starts then you probably have a broken comutator contact on the armature and it requires a trip to a motor repair expert.

That's all that I can think of.

**Chris in MS** · 09-18-2005, 06:24 PM

Hi Rich,

Thanks for your help. I found the problem. The second thing I checked when I started this investigation was the on/off switch. It was good. This afternoon I pulled the motor apart and checked the brushings as you suggested and then the field windings and the windings on the armature--all of those were good too. After all of this I was pretty frustrated but I checked everthing else again--cord, o/o switch, etc, but this time the o/o switch did not work. I pulled the switch, opened it up, and found it was filled with fine, hard-packed sawdust. I cleaned it out and reinstalled it--router works! $250 saved, but now I can't justify to my wife getting the new 3.25 hp router that I had already picked out...

Thanks again,

Chris

**rrich** · 09-18-2005, 10:46 PM

Chris,
Filled with sawdust? That's astounding! Is there some way that you can seal the switch? Even a bit of a plastic bag held in place with silicone would be better than nothing.

**Chris in MS** · 09-19-2005, 12:14 PM

Rich,

I was surprised too. I use the router almost exclusively in a table with no dust collection, but I’m still not sure how so much sawdust got forced through the very small crevices to fill up the switch, which is located on the side of the router and obviously under the table. Maybe sawdust (and I mean dust) on my fingers is forced in when I operate the switch. The switch cover is sealed in the back so I don’t see how any suction could have been created when the router is on. I have a cheap Skil ROS that has a sealed, rubber-covered switch. I’ll probably do as you suggested and make a switch cover out of a plastic bag.

Seems like switch problems may be common--I saw the DC failure post below.

Thanks again for your help, I appreciate it.

Chris