# Won't power on, new ac contactor



## Driveslayer45 (May 24, 2019)

Good evening all,

I have a similar model to a 9729 3 in 1 lathe, mill, drill. It shut itself off, lost power, for no apparent reason. The AC connector tripped, I guess. Anyway I looked the machine over for shorts, nicks in the wires, the usual stuff. Tested the ER switch and power on switch  with a multi-meter, they checked out. If i manually engage the AC contactor the machine operates, so I purchased and installed a new ac contactor.

I hope someone can give me a suggestion.


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## jbobb1 (May 24, 2019)

Does the new contactor work or is it the new one you're having problems with?


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## markba633csi (May 24, 2019)

No power getting to the contactor coil, sounds like.  Need to trace that circuit.   The coil could be 120 volt ac or some other voltage like 24, with a step down transformer somewhere
Could be a bad switch or a loose connection-  is there a diagram for the machine? 
Mark


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## Driveslayer45 (May 24, 2019)

The new contactor doesn't work either. The schematics for the grizzly match my machine, but they are fairly simple. I've checked the wires and connections to ensure they are tight, to no avail.


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## jbobb1 (May 24, 2019)

As Mark mentioned, you need to check that the contactor solenoid is getting power. Do you see any fuse blocks? Maybe a blown fuse.


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## markba633csi (May 25, 2019)

The 9729 diagram is very simple.  There are several switches in series with the coil, including a microswitch.  By the way is the emergency stop switch pulled out?  Is the microswitch jammed up ? (I believe it's the safety cover switch) make sure you can hear it clicking
Try jumpering the switches one at a time, starting with the microswitch if none of the above works
be careful


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## GL (May 25, 2019)

We had a similar issue at work the other day.  Contactors have a thermal overload on the control side (sometimes called "the heater").  If you can push the contactor closed manually, and the spindle runs, the problem is on the control side not the power side.  In our case all the overloads were in series, so when one dropped it took everything down - pumps, spindle, fast traverse, etc. We tried a new contactor also - not.  Checked the overloads until we found the open one, got it reset and everything worked.  Contactors seem to work about the same so the instructions for the new one may help with the old one.


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## Driveslayer45 (May 25, 2019)

Thanks for all the help. I found the issue. There is a safety switch on the cover of the mill.. when you screw the cover down it disengages the safety, let's power through.  That switch failed... Pulled my hair out chasing wires as that switch was not on the wiring diagram


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## markba633csi (May 25, 2019)

Yay!  I suspected that switch


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## Ulma Doctor (May 26, 2019)

manually pushing in the contactor is the simplest test to see if there is a problem in the control circuit or the contactor.

if you push in on the contactor, and the machine runs, you then know the problem lies in the control circuit
if you push the contactor and it doesn't run, you know there is a problem with the contactor, or incoming power


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## Driveslayer45 (May 27, 2019)

yeah the manual was certainly lacking on troubleshooting advice.  but its resolved now and on to other issues.  my lathe motor has now stopped running in forward, it just kinda buzzes … reverse seems to work.


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## jbobb1 (May 28, 2019)

It sounds like the start winding isn’t in the forward circuit for some reason. Did this just start after replacing the contractor?


Sent from my iPhone using Tapatalk


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## Driveslayer45 (May 29, 2019)

it worked for several hours after replacing the contactor then just stopped working. it was cutting fine, stopped to measure and it wouldn't start again in forward, but it would run in reverse.  I am hoping its the 50Uf run capacitor.


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## markba633csi (May 30, 2019)

It could be an unexpected cap failure, on the other hand it's a good rule of thumb to suspect the last thing you did.  In this case, are you sure the replacement contactor is functionally the same as the old one and is wired up exactly the same?  Problems with only one direction would tend to indicate a problem with the reversing switch...or wiring thereto


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## Driveslayer45 (Jun 1, 2019)

I think the contactor is working properly since the machine worked for several hours after changing, but how would I test it, or test the switch?


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## markba633csi (Jun 2, 2019)

Does it work in both forward and reverse when you manually engage the contactor? If not then it may be a problem with the reversing switch
You would need to remove the switch and test it for continuity on the bench- does this machine have a lot of hours on it?
Check the wiring to the switch first in case there is something loose or freaky- shut power off
I'll take another look at the Grizzly diagram, see if there's anything else it might be


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## markba633csi (Jun 2, 2019)

This machine has two motors correct? And two reversing switches?


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## hermetic (Jun 2, 2019)

If you select forward, and the contactor pulls in, then it is either a motor fault, or the feed to the switch side of the contactor is not there. If the contactor does not pull in, suspect the safety circuit again. If the motor is buzzing, does sound like start capacitor fault.


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## jbobb1 (Jun 2, 2019)

Because it's working in reverse, I suspect the reversing switch. The way it operates is, it's reversing the start windings. Because it's buzzing in forward, I believe the starts aren't in the circuit.


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## markba633csi (Jun 2, 2019)

According to the Grizzly diagram the contactor just supplies mains power to both motors, each with it's own reversing switch.. it has to be the switch
these chi-com switches are not real reliable


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## Driveslayer45 (Jun 2, 2019)

I have confirmed I do have a switch problem by comparing the readings between the mill switch and the lathe switch. However, even when I swap switches I do not have forward and reverse.. perhaps both switches have failed in different ways?

Anyway I have. Switch on order from grizzly, it should be in on Tuesday.


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## Driveslayer45 (Jun 3, 2019)

does anyone have a recommendation on a different switch to use besides the grizzly one?


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## markba633csi (Jun 3, 2019)

Not really, anything heavier duty would be physically larger and might not fit in the space provided. Mounting a larger switch in a different location might be possible.
The original switch fails because it has to handle all the motor current.  The factory should have used additional contactors in between but that would have cost more.


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## Driveslayer45 (Jun 3, 2019)

Well i have a switch on the way from Grizzly, and i found what appears to be a similar switch on amazon for about $15.. i ordered it as well to compare.

I do have concerns about my motors, they are old (20 years), i don't know how many hours as the machine has sat for years until recently, last 3-4 months i guess.  Grizlzly says the motors are no longer available, when i do lose one, assuming the switch solves my current issue, I am not sure what i am going to do... might try a dc motor conversion....


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## markba633csi (Jun 3, 2019)

Variable speed on a lathe is nice to have, some people take treadmill motors and adapt them


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## jbobb1 (Jun 3, 2019)

You could also try a 3 phase motor and a variable freq drive. Less maintenance than a dc motor, unless it's brushless.


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## Driveslayer45 (Jun 3, 2019)

I've read that you lose significant performance with a 3 phase and vfd. treadmill motor was the route i was thinking if i have to go that way.


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## Driveslayer45 (Jun 4, 2019)

My issue is resolved. I replaced both switches and all is working as it should. I ordered a switch from grizzly that dropped right in. I also ordered a 20amp switch from Amazon, both came in the same packaging with Chinese instructions. The Amazon switch appeared heavier, has a more solid feel when you turn it, but required some 'adjustments' before it worked right, but at $12 compared $47 I think it was a deal. And with a new working switch in hand to compare I know where the original switch was broken So i could possibly fix it for a spare..


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## markba633csi (Jun 5, 2019)

Good deal,  would be helpful if you could post the part #s/vendor info in case someone else has the same problems


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## Driveslayer45 (Jun 5, 2019)

This is the switch from Amazon I ordered. i did have to open it up and adjust the plastic wheels inside to get them to open and close at the correct spots.




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						uxcell Changeover Switch 3 Position Rotary Selector Cam Switch Panel Mount 12 Terminals Latching Ui 550V Ith 20An Red: Amazon.com: Tools & Home Improvement
					

uxcell Changeover Switch 3 Position Rotary Selector Cam Switch Panel Mount 12 Terminals Latching Ui 550V Ith 20An Red: Amazon.com: Tools & Home Improvement



					www.amazon.com
				




The Grizzly switch part number is: P9729318A      
i also ordered the 50uf capacitors for the motors, one had blown off awhile back. P9729111T-1V3   R CAPACITOR 50M 450V 4 X 1-7/8 V3.01.12

frankly i am not sure what the 50uf capacitor is for. after i installed the new switch the motor worked fine, forward and reverse, before i installed the 50uf capacitor.


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