Wrong diagnosis and dumb move by me

[Jim Rimmer]

I posted last night about my Craftsman saw motor crapping out. I took some of the advice and started trouble shooting tonight. First step was to make sure the switch was not clogged with sawdust. In taking it apart I noticed a lable that said "The power relay in this switch is gravity sensistive. Never turn on the power until the switch is mounted on the rails and the saw is upright." When I installed the T2 fence I had to relocate the switch and did not notice the label (in my defense, it was on the bottom) and did not put it in the correct position. So I put it in the correct position but saw tries to start but won't run. Did I burn up the relay? How do I check it? I'm going to check the Sears site and see if i can still get a replacement.

[george wilson]

Can't you just use a regular house type wall switch in a metal box? Why the need for something like the original,which you probably won't get from Sears.

It could be a standard type of switch which a good electrician would recognize under a different name.

[David Christopher]

Jim, I would bypass the relay and see if the motor will run before I spent more money and find the motor maybe still bad...if the motor runs when you bypass then go buy the relay

[Jim Rimmer]

Can't you just use a regular house type wall switch in a metal box? Why the need for something like the original,which you probably won't get from Sears.

It could be a standard type of switch which a good electrician would recognize under a different name.
I just checked the Sears website and believe it or not, they have the relay in stock. I wondered about using a regular switch, too, but don't know much about motors and relays (my experience is in electronics, not electrical). For some reason they put a power relay on it when it was designed. Can I take it off and just go straight through a switch? :confused:

[Myk Rian]

Can I take it off and just go straight through a switch? :confused:
That would certainly be cheaper than buying the relay. I use a household switch for my 2hp DC, so it should handle that saw motor.

[Steve Rozmiarek]

There are actual motor switches that look like a household switch that would tolerate the use better then the standard household switch. Might try to find one of them at your borg.

[Kyle Iwamoto]

IIRC, from high school, the purpose of the relay is to prevent the saw from restarting, if you lose power. A primitive magnetic switch. That would of course depend on the start switch, if it's a push on and release switch, that may be what it is. A no restart saw IMO is a good feature. Using a light switch would work, but will defeat the feature.

If it's gravity sensitive, did you try and mount it the correct way and try to start the saw? May save you a trip to teh BORG and/or Sears. Every time I go there my checkbook gets lighter.

[Rod Sheridan]

The relay is not to turn the saw motor on and off, it's to turn the starting winding on and off. (There isn't a centrifugal switch in the motor).

The relay doesn't have a return spring, gravity does that function. Turn it upside down and it runs the starting winding constantly, which can "let the smoke out" of the motor in short order.

When you turn on the power via the built in toggle switch, the motor isn't rotating. The high starting current pulls in the relay, providing power to the starting winding.

Once the motor is up to a reasonable speed, the current drops and the starting relay drops out, de-energizing the start winding.

You can use any suitably rated switch to turn the saw on and off, however you cannot eliminate the starting relay.

Regards, Rod.

[lowell holmes]

I've been using a dpdt household (commercial grade) toggle switch on my Delta CS for 9 years. I have running on 220v. The only thing I don't like is there is no safety paddle on it to turn it off by bumping it with a knee or leg. The oem switch only lasted a year.

If I really tried, I'm sure I could come up with something though.

[Chip Lindley]

What a *jury-rigged* (epithet deleted) way to keep from putting a decent motor on a saw!! Sears saved a few bucks by letting gravity do the work of a spring, and using a cheap motor without centrifugal contacts! But, it cost you in the long run if you fried your motor because of a hidden tag!
WayToGo! Sears!!

[george wilson]

I have had a 20 amp household switch on my 3/4 H.P. drill press since 1964. The original motor went bad last week,but the switch is still good. it depends upon how large your motor is,and if 20 amps can handle it. Magnetic is better,of course,so your machine won't start back up after the power comes back on.

Chip,that Sears motor from back then ran for long enough,don't you think? Probably an Emerson rebadged.

[Bruce Wrenn]

What a *jury-rigged* (epithet deleted) way to keep from putting a decent motor on a saw!! Sears saved a few bucks by letting gravity do the work of a spring, and using a cheap motor without centrifugal contacts! But, it cost you in the long run if you fried your motor because of a hidden tag!
WayToGo! Sears!!I guess Franklin ( they make submersible pump motors, more than anybody else in the WORLD) is also cheap. Most if not all three wire well pumps have a current sensing relay for the start windings, along with the compressor in your AC, and refrigerator. I have a 30+ year old Skill bench grinder that uses a current relay to operate the start windings. Delta uses same set up on some of their disk/ belt sanders. How would YOU service a relay in a hermatic compressor? You can't take it apart. Being exterally mounted isn't a sign of cheapness, but of quality engineering, IMHO. I don't havve to disassemble a motor to replace relay (aka start switch.) Imagine if a submersible pump, 200'+ down in a well had to be pulled to sevice start switch. We charge around $350 to pull pump, but only $65 labor to replace control box. located at top of well. Just because you aren't familar with a system, doesn't make it bad. Just different from what you have delt with before.

[Jim Rimmer]

Latest in the saga: Took the relay apart and cleaned contacts and reassembled. Saw just buzzes. Turned it off, gave the blade a spin and then hit the switch (I know, not safe. It did take several tries because of my inability to get to the switch quickly and my fear) and the saw started up. Bypassed the relay and went directly through the switch and same results. If I turn it off and let the blade coast for awhile and then hit the switch it starts back up as long as I don't wait until it stops. That tells me the motor and bearings are OK.

So I guess I have to have the relay. I checked it out and there's really not much to it. I read zero ohms across the coil and I would think there should be some very low resistance. If I put an ohmeter on the contacts and rotate the relay in my hand, it goes from open to closed but apparently does not pull in when power is applied. So I guess while I had the relay horizontal I burned up the coil maybe accounting for the smell that I thought was the motor.

One thing that has me puzzled. What/how does the relay drop out after the saw starts?

[Dave Lash]

The fact that the motor runs when you spin it to get it started means that the run winding is OK, but the starting winding may still be burned out. The function of the starting winding is to give the motor it's initial rotation, and then the run winding keeps it going. Once the motor is spinning, the starting winding is then taken out of the circuit either by a centrifical switch or as in your case a relay. If you have an ohm meter you could check the starting winding for continuity; if it is good, it will probably read close to 0 ohms, if it has no continuity, the winding is open and is bad. When the relay was not mounted vertically, and you started the motor, it probably kept the starting winding energized and may have burned up the winding, resulting in the smell you noticed. Under normal operation the starting winding is energized for just the first second that power is applied to the motor, therefor it is usually a fine gauge wire that will burn up if left energized too long. The relay is pulled in by the high starting current of the run winding on initial power up, and the relay contacts energize the starting winding; once the motor is spinning the run winding current drops to its normal value, and the relay drops out as the lower current isn't enough to keep it energized.

[Bruce Wrenn]

What a *jury-rigged* (epithet deleted) way to keep from putting a decent motor on a saw!! Sears saved a few bucks by letting gravity do the work of a spring, and using a cheap motor without centrifugal contacts! But, it cost you in the long run if you fried your motor because of a hidden tag!
WayToGo! Sears!!Springs break, but gravity doesn't. Works 24/7/365 without a break. It simply a case of reading the directions, which most of us (myself included) don't do. Directions, what directions?

[Ken Fitzgerald]

Jim,

Most ac motors use a starting capacitor inconjuction with a centrifugal switch on the motor. When the motor isn't turning, the switch is closed and the capacitor is in the circuit. When you turn power on, the capacitor provides a phase shift so there is a phase difference between the voltage applied to the two motor windings. This causes the motor to start and spin in the correct direction. Once the motor achieves it's normal operating speed, the centrifugal switch opens up removing the starting capacitor from the circuit.

I'd pull the starting capacitor and check it with an ohm meter to see if it is shorted or open. If you don't have an ohm meter, a local motor rewind shop should be able to test it for you and sell you a replacement.

[Jerome Hanby]

If you are going to buy an ohm meter for this kind of testing, I suggest shopping around and finding a Simpson meter with the analog movement. They all look the same, a black rectangular "cube" with rounded corners about nine or ten inches tall, seven or so wide, and three or four thick. You just can't beat an analog meter for testing caps, the smooth swing of the needle as the cap charges is much easier to interpret than the rapidly changing numbers on a digital display. Plus the analog meter has more "ummph" than the digital versions, important when testing semiconductors.

Digital meters are nice too, especially if it contains a micro-ranging ohm meter. Great for tracking down shorts.

[Chip Lindley]

I see I've struck a nerve Bruce! Sorry, but we are talking *consumer-grade* tools here, not expensive deep well pumps! My last deep well 3/4hp pump lasted 19 years! I don't think Franklin makes Sears motors!

The OP's motor and its *external* parts are so-engineered to cut cost, NOT for convenience! A decent capacitor-start, induction run motor would be wayy more expensive for Sears to include, than their *solution*! Sears' price-point won't allow it.

I outgrew Crapsman yearzz ago, even when they DID include cap.start motors on their stationary machines! Sears used to have a *Commercial* line that was very usable. (Other name-brands with the Craftsman label on them!) Don't tell me how great Sears machinery is now. I Don't buy it! (literally OR figuratively)

On a (sorta) postive note: most ANY Sears TS fence Today is light years ahead of what I had to put up with in the '70s! A decent motor on a TS with an unusable fence was still a POS! Seems now its just the inverse! But, by the '80s I moved UP to an old Rockwell and never looked back!

[Bruce Wrenn]

Actually, a relay is cheaper to make and install than a centrifical switch. (I can buy Klik-Ons for a couple bucks each. The fit small compressers in ref. devices.) Newer ones are solid state, which is even better. Only two moving parts, which are actually an assembly. Can be mounted almost anywhere. Doesn't require precision tolerances. A couple holes, threaded and screws. SuPro makes a combination relay / capacitor, that retails for less than wholesale price on most cent. switches. I have wondered about adapting one to a woodworking motor that has a non fixable cent. switch. Sometimes look at the switch from a Grizzly TS motor, and then look at the switch from a Marathon / Baldor / Century. Big difference in the quality. Even better, look at how cheap switches are in some GE motors. (They are the illustration for the word cheap.) You "down rated" (polite term) Sears for using a relay to save money, but it is actually a better product from service stand point. As for "expensive" well pump motors, there are no cheap ones, only dependable ones, as you stated. I don't expect any motor on a woodworking tool to last 19 years, without some kind of servicing. I also moved up to a Rockwell saw. I have a Model 10 that is so old, that the rods and trunions are a one piece casting (cast iron.) I have never seen another like it. I have a "newer", cheaper made saw (also Rockwell) that has the steel rods connecting the trunions.

[Jim Rimmer]

I guess the technology is OK but using a gravity return with the warning label on the bottom out of sight was the problem. Since I didn't see it ( and, yeah, I should have looked closer) it cost me a saw. It appears that having the relay horizontal caused it to not drop out since it was gravity, not spring, activated and the current burned up the starter windings. How much would a spring have cost Sears? Sears doesn't sell the motor anymore and repair or replacement at a motor shop will cost more than an equivalent new saw.

So I am looking for a new saw. Maybe a used one from CL or the Grizzly G0661.