I took both capicators to a shop today and he tested them with a capicatance meter and he said they were both Ok... It did not test it under heat conditions...and I don't know if the meter puts a load on them. So, I purchased a new start capicator anyways since there were just $5.00

Installed the new start capicator and the same thing is happening. The motor is not kicking into high gear with no belt load

I tested it first thing this morning and it was working fine when it was cold with the old start capicator--full speed with no belt load.

Am I SOL? Its definetly heat dependent. He said it could either be the switch or its the windings on the motor. I don't see how the switch could be heat sensitive. So is the motor gone?

 

Hmm - not sounding good

You might try taking the motor out, and measuring resistance from all connections when cold, making a note of them. Preheat your oven to it's lowest temp settings for 30 minutes, and then put the motor in the oven for several hours. Take the measurements again.

It'll be tough getting accurate measurements with a typical multimeter, as the resistance levels will be just a few Ohms. It would be easier to measure resistance by using a constant current source, and measuring the voltage drop across the conductor instead. 1 Ampere through 1 Ohm = 1 Volt drop across the load.

 

Well I just checked the switch with a VOM and it seems fine to me. Really the only thing left now is the Run capacitor and the motor.

I'm not sure testing the motor in the oven makes much sense because by the process of elimination, it can't be much more than that.

It can't be the run capacitor right? When I talked with HarborFreight, they said that it was the run capacitor "not" the start capacitor given by description. They said if it was the start capacitor, it would never start up or turn over in the first place.

Is there any parts serviceable in the motor? Is it possible there is some kind of thermocouple in there? Its amazing how exact the problem is to heat of the day.

 

Well, try testing the run cap when it's been preheated.
But since you won't have an oven available at the shop you took it to, try placing it on your vehicle's intake manifold to get it good and hot during the drive there. Borrow the wife's oven mitts. Leave the capacitor on your intake manifold with the hood (bonnet for the UK crowd) down to keep it warm until the tech is about ready to test it. Pick up the cap with one mitt, and put it inside the other mitt to keep it hot while testing.

 

I don't think its the run capacitor. First, it tests correctly with the VOM and I can see the VOM charging the capacitor....with the resistance increasing.

Also, I tried putting the capacitor in the freezer for 5-10 minutes and let it get good and cold. Then I took it out with a compress surrounding it, hooked it up and same thing.

There are no brushes in this type of motor right?

I really think there is a thermocouple sensor inside of the motor whose job it is to sense the internal temperature of the motor and to shut down the run windings when the motor is overheated....

Can the motor be taken apart??
....I see screw bolts but when I take those off...nothing is moving and the cap stays on. If I could get it apart, I could also oil the bearings for good measure and see if there is anything obvious.

 

According to the advertisement for this saw...

Powerful dual capacitor motor with sealed bearings and thermal overload protection.

Thats whats failing.... I need to somehow disable this thermal overload protection or figure out a way to fix it. It has to be in the motor somewhere.

 

Ok, I took the motor apart....
No brushes as I suspected.
No obvious burn marks, rubs or anything obvious on the windings.
And no "Thermal coupler" or anything to suggest what they are referring to or what could be possible thermal sensitive.

I'm at a loss.

 

Hmm. Perhaps the thermal overload breaker's contacts are burned from having been cycled so many times.

It might be integral to the wiring on one of the windings, or buried deep in the motor somewhere. Hard to say offhand. It's also hard to say what it might look like, as there are a multitude of designs out there.

Can you get a manual/datasheet for the motor? Do you have a part number and manufacturer for it? There may be a plate fastened to the motor which gives that information. If not, what is the manufacturer and model of the saw?

 

Its a Model: TC250B Motor. Made in China.
Its a Chicago Electric Power Tools 2.5 Horsepower 10" Industrial Tile/Brick Saw.
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=95385
Product Manual

I took it apart...there is no thermal couple in there!!! Or, its hidden in the windings. Nothing fancy at all. The wires go right into the windings. No obvious problem with the windings.

The bearings are sealed and in good shape. I lubed them a little.

I thought I had it, because when I took the back of the motor off on the contact switch, one of the wires going to the switch broke off, and way too easily, like it definetly was partially broken before hand and just hanging on with a thread. I got all enthusiastic because it seemed like that was it. I put it back together, turned it on, and poof --- same problem.

Assuming the new startup capacitor doesn't make any difference. Its a 145-174 uFD where as the one in it before was 150MFD. It seems to be turning slightly slower on the startup than before, but that could just be my imagination...before I took it apart as well.

 

Well, if you can't find the thermal breaker, I'm not sure what to tell you.

Did you inspect the "contact switch" as you call it? Having that wire "hanging by a thread" as it was, that would be a high-resistance connection that would generate heat, and may have caused damage to the contacts inside the switch. If it isn't readily dissassembled, you might try substituting a different switch of suitable ratings temporarily.

 

Sorry to come to the party late. I reviewed all the comments. Way back on page 1 you commented that the motor ran fine without the belt. Does it also run fine without the belt when hot?

If so, I would further investigate the spindle. It should turn freely whether hot or cold. Test when cold, then warm up until the problem occurs, remove belt and re-test for free turning. One possibility is that the bearings in the spindle are pre-loaded. If that is not done correctly (i.e., bad tolerances), they can seize when warm but be free when cool.

If that is the case, replacing the bearings can be done, but you will need a gear/pulley puller and probably an arbor press. Do you have any friends who are machinists? Where are you located?

John

 

Did you inspect the "contact switch" as you call it? Having that wire "hanging by a thread" as it was, that would be a high-resistance connection that would generate heat, and may have caused damage to the contacts inside the switch. If it isn't readily dissassembled, you might try substituting a different switch of suitable ratings temporarily.

There are 3 switches.

1. A circuit breaker switch which is what is actually switchin off at about 15 seconds when the motor stays in low speed. I have checked the breaker and its continuous when closed and when tripped its not continuous. Don't see anything wrong with it.

2. There is a on/off switch which has a black wire on the bottom next to a white white...on top there are two red wires. I have checked the switch in the off position and there is no continuity between top and bottom. There is 110 between the black and white. When the switch is in the off position, voltage appears to go to both red wires and it is continuous. Don't see anything wrong with it.

3. The centrifugal switch on the motor. This has 2 black wires going to it from inside of the motor. One of these was hanging on by a thread and it broke while I was disassembling it leaving the circular post on the screw. I repaired this but it didn't appear to be the problem.

 

Sorry to come to the party late. I reviewed all the comments. Way back on page 1 you commented that the motor ran fine without the belt. Does it also run fine without the belt when hot?

If so, I would further investigate the spindle. It should turn freely whether hot or cold. Test when cold, then warm up until the problem occurs, remove belt and re-test for free turning. One possibility is that the bearings in the spindle are pre-loaded. If that is not done correctly (i.e., bad tolerances), they can seize when warm but be free when cool.

If that is the case, replacing the bearings can be done, but you will need a gear/pulley puller and probably an arbor press. Do you have any friends who are machinists? Where are you located?

John

Thanks John. No it doesn't run fine now without the belt "outside". It only ran fine when I took the motor out of my house which was under A/C and the motor set in there for about 2 hours. Also, while the motor was in the house, I tested it without the belt and it ran fine as well. It instantly spun up. I took it outside put it on the saw, hooked it up on the belt and it ran fine. I turned it off, got my wife turned it on and it was still running fine for her to see. I was doing the dance.

Then I put everything back together. It took about 30 minutes. And at the end, I tested it and it was no longer working. I took the belt back off and it still wasn't working. The next morning I tested it and it was a very cool morning and it worked fine again.

Its not the bearings on the motor. I can spin the motor and it will spin about 4-5 full spins from just one manual spin of the pulley. The bearings are completely sealed. There is no play in the bearings. And the bearings make no sound. When I took the motor apart, I spun the bearings and there were flawless. I'm 100% sure its not the bearings. I did oil them and gease the outside but it didn't have a huge effect.... They still spin with ease hot or cold and there is no difference in the spinning.

Also, the spin better than the bearings on the saw shaft...those are not as good....but those would be exposed to the water normally of the saw.

I don't see how the heat can effect the windings...that makes no sense at all to me.

 

OK, I didn't know the breaker was external to the motor.

I think that's where your problem is. I'll bet it's contacts are pitted. The pitted contacts are generating heat, which cause the breaker to trip after a period of time.

 

OK, I didn't know the breaker was external to the motor.

I think that's where your problem is. I'll bet it's contacts are pitted. The pitted contacts are generating heat, which cause the breaker to trip after a period of time.

How can that be? The breaker is doing its job. It needs to trip after 15 seconds because the motor is not coming "out" of the start capacitor...its tripping because the motor is overloaded and not coming up to speed.

I guess I could temporarily hook those two together as long as I don't try for longer than 10 seconds.

It came up to full speed again this morning...but only once. I am totally stumped.

 

Ok, I short circuited the trip breaker and directly connected the leads going to the breaker. Same thing.

 

There is a device called a Motor Protector. See http://www.precision-controls.com/mot_prot.htm

More...these come from China...
http://jingmichina.manufacturer.***...l/Thermostat/1005085335/Thermal-Protector.htm

I willing to bet this is my problem...I just don't know where the thing is.

Does anyone know where this would be located?

 

My wife figured it out....

Its the plug/outlet. Even with no extension cord, the outside plug is not delivering enough amps to run it. We are able to get the motor to run outside reproducibly now.....how?.....with a small extension cord to the inside outlet.

Even plugged directly into the outside outlet....it couldn't get enough juice. It wasn't temperature, it was the outlet I was using from the inside to outside. And even stranger, somehow first thing in the morning, it was able to pull enough amps through the outside outlet. Even with an extension cord to the inside its working better than a direct plug into the outside outlet.

I can't believe I just wasted all this time on something as stupid as a plug/outlet.

 

Well --- blew the brand new Start capacitor on the second turn-on in the house...had to go back to the old one.

Running a 12 guage extension cord from inside the house seems to work ok. Cut 8 bricks...

 

My wife figured it out....

Its the plug/outlet.

Geeze!
Well, better find out why. I am NOT an electrician! I strongly suggest having an electrician fix it. Reason is, if there's an electrical fire and the inspector finds some non-standard wiring was performed, the insurance company may refuse to pay your claim!

Get it repaired & up to code. I can only suggest that 20A outlets are good for a garage/workshop - but every piece along the way, breaker, wire gauge, splices, outlets, etc. must be rated for that kind of current, and enclosed according to NEMA standards, national and local electrical codes.

Only a licensed electrician in your area can properly advise you. I ain't that person!