DC motor on the fritz

[Matt Calder]

All,
Hopefully someone can help with this. This morning my DC stopped working. Rather than the usual whooosh, when I turned it on it just hummed. I thought something might be wedged in the impellers so I took off the pipe and spun them. There did not appear to be anything wedged. I hit the switch and, whoosh, OK! I put the pipe back on and went to do some cutting, I started the DC, and all it did was humm. It turns out that if I give the impellers a nudge, the motor goes.

My question is, is this something I can fix? The DC is only a month old, should I send it back? I'd rather learn how to fix it and do that every now and then, but if it is a sign of some terrible defect, I will return it.

Matt

[Jim Becker]

One month old - Warranty. Let them fix the problem Matt.

[glenn bradley]

Depending on the source of the DC I would think they would just send you the motor. Sounds like a classic starter issue.

[Joe Foggia]

It sounds like a capacitor is either bad or the electrical connecctin to it is loose or broken. It will look like black cylinder about 1.5" or so and be maybe 3" to 4" long with a couple spade connectors on top. They are used to boost the startup current to get the motor going. The fact it is so new leads me to suspect the connection to the motor. Unplug the machine and find the capacitor and check the connections. If that doesn't work then call the service dept. and have them send another one to you. Easier than sending the motor back. You can also get an equivilant locally. They are rated in farads. Just replace with the same voltage and farad value and you will be good to go. Many large motors use caps to get started and it is very common to lose them after a few years. Easy fix normally. Joe

[Bob Dodge]

I second looking at the start capacitor contacts. What dc do you have?

Bob

[Matt Calder]

Joe,

It looks like you are spot on. The capacitor measure 0 MFD using my multimeter and shows no resistance between the poles. Any suggestions what type of place would sell such a thing? Too big for Radio Shack.

The DC is a Bridgewood 2HP from Wilke. I'll give them a call, I'm sure they'd rather send a new capacitor than a new DC.

Matt

[Matt Calder]

Joe,

I called Wilke Machinery service department and the guy (Kurt?) knew right away what was wrong. It was something called a centrifugal switch, and I think its purpose is to discharge the capacitor at the right moment. So you were right about what was not happening. The fix is quite simple and some might find this information useful.

The centrifugal switch is mounted on the motor arbor. I took off the fan cover, the fan, and one more cover. The switch needs to be moved in a wee bit. There is a set screw, loosen, push, tighten, done.

Is it me, or after doing a repair on a machine of this sort, one involving opening it, and going beyond adjustment. Doesn't it feel like you really own the machine? So many of the larger tools in my shop are still tenants. The DC is now a family member.

Thanks for the help,

Matt

[Ray Moser]

Any electrical supply should sell motor capacitors-that is where I bought one for my air compressor. A good capacitor should show no resistance-an open circuit. If it shows resistance it has an internal short and is kaput. I don't know what kind of multimeter you have that will measure capacitance. Most only measure AC or DC voltage/current and resistance. A meter to measure capacitance is more complicated.

[Matt Calder]

Ray,

My multimeter is a deluxe version bought when I was doing graduate EE work. I still don't get why the capacitor works when it is measuring as shorted. It does work though. But in the end, I don't care if the capacitor works or not, I care if the motor starts, and, now it does, go figure.

Matt