7" Milwaukee Grinder Won't run?

[jbaccell]

I would bet that the relay is stuck (contacts welded). I would take a Dremel thin kerf saw and cut the plastic at the seam line on the side with the two male push on terminals (just on the three exposed sides), then delicately pry the part open enough to examine and possibly free the contacts. Once done, take a soldering iron and "weld" it back together.

It's busted, so what do you have to lose.

The saga continues…. I was able to get it apart as you suggested. The contacts did not appear stuck but I might have freed them when taking it apart.

I did clean them and put the relay back together. After wiring it up and installing the capacitor, I plugged it in and the grinder fired up. The problem now is the capacitor began smoking and got very hot.

Any insight as to the reason for that? The relay is not dropping the capacitor out?

Again, my continued thanks.

Joe

 

[tq60]

My policy is simple...
It was broken when I started.

When finished the hope is ot is broke a little less

Sent from my SM-G781V using Tapatalk

 

[SLK001]

The problem now is the capacitor began smoking and got very hot.

Any insight as to the reason for that? The relay is not dropping the capacitor out?

Is the capacitor an exact match for the original? The correct voltage cap should be able to stay energized almost forever. Are you sure that the original cap was bad? The original symptoms indicated that the start cap wasn't being switched on (or the cap was dead, dead, dead...).

Can you tell if the relay is normally open, or normally closed?

 

[jbaccell]

Is the capacitor an exact match for the original? The correct voltage cap should be able to stay energized almost forever. Are you sure that the original cap was bad? The original symptoms indicated that the start cap wasn't being switched on (or the cap was dead, dead, dead...).

Can you tell if the relay is normally open, or normally closed?

When I tested capacitance of the old capacitor, it was dead. It was rated for190 microfarads. I ordered a replacement which had a rating range of 160-193 and when tested before installing came up to about 203 microfarads.

After opening the relay and cleaning the contacts as you advised, I wired everything back up and as mentioned, the grinder fired right up but the capacitor made some crazy sounds and spurred out gas/fumes and got very hot.

I’m not sure if the relay is normally opened or closed, I will check it with a meter when I get home later.

I can say it enough how much I appreciate the assistance and sharing of knowledge by you and other members of the forum. I would not have a clue how to fix this without it.

Thank you,

Joe

 

[brino]

Joe,

It sounds like the microfarad range for your new capacitor was close enough to the original.
But what about the voltage rating?

Most relays are fairly simple to "bench test". (out of circuit; no line voltage or motor attached)
Put an ohm meter across the contacts (I use a low-R range with beep sound).
Apply a test voltage to the coil, the meter should change readings/sound.
The relay datasheet from post #2 should tell you the coil voltage range.
I'd probably start with 12VDC.
Be careful if your using any dangerous voltage!

Stick with this, we will help get it figured out!

Brian

 

[jbaccell]

Joe,

It sounds like the microfarad range for your new capacitor was close enough to the original.
But what about the voltage rating?

Most relays are fairly simple to "bench test". (out of circuit; no line voltage or motor attached)
Put an ohm meter across the contacts (I use a low-R range with beep sound).
Apply a test voltage to the coil, the meter should change readings/sound.
The relay datasheet from post #2 should tell you the coil voltage range.
Be careful if your using 120VAC!

Stick with this, we will help get it figured out!

Brian

The voltage rating is of the new capacitor is 120vac. The old one I guess due to its age reads 110vac.

Again, thank you, I will perform the tests you graciously outlined for me.

Joe

 

[brino]

okay I just read the relay datasheet.
It only gives info on pick-up and drop-out current.

it is meant to go in series with the motor winding with 120V applied to the pair.
That means it is meant for less than 120V as the two coils will split the voltage.
So you should test it with a much lower voltage!

I'd start with 12VDC (as I updated in my post above) applied to the coil for a few seconds for bench test.
If that does not work then I'd go higher, but I have the luxury of an adjustable bench power supply.

The problem is that you need 15-18Amps thru the coil to activate it......perhaps not worth the difficulty to test....sorry.

Brian

 

[jbaccell]

okay I just read the relay datasheet.
It only gives info on pick-up and drop-out current.

it is meant to go in series with the motor winding with 120V applied to the pair.
That means it is meant for less than 120V as the two coils will split the voltage.
So you should test it with a much lower voltage!

I'd start with 12VDC (as I updated in my post above) applied to the coil for a few seconds for bench test.
If that does not work then I'd go higher, but I have the luxury of an adjustable bench power supply.

The problem is that you need 15-18Amps thru the coil to activate it......perhaps not worth the difficulty to test....sorry.

Brian

No need to be sorry, Brian, I am the one who is sorry to keep asking so many questions. I assume there is no way to eliminate the relay? If the start capacitor remains connected, will it damage anything? Will it even start the motor? Sorry for all the questions..

 

[jbaccell]

First, I profusely thank all of you who took the time to assist me, I do appreciate it.

I worked on the grinder again this morning following the advice I received here. I hooked the starter relay to a 12 volt battery and she clicked and the readings on the ohm meter changed as I was told to look for by Brian. I then installed another properly sized capacitor and reassembled everything. While the grinder was on its back, I plugged it in and turned the switch on. She fired up and seemed to be working properly.

I bolted the grinder back to its stand, flipped the switch and all I got was a hum (WTF?) I took it back off the stand and again placed the grinder on its back and before I did anything, I plugged it in and hit the switch and wouldn't you know it, she fired up. The relay does have written "TOP" written on it so I am wondering if that makes a difference how its oriented?. I turned the grinder to the upright position, and it just hummed again.
So, I changed the orientation of the motor relay and put everything back together, placed the grinder on its stand, plugged it in and hit the switch...Joy, so I thought.

I let it run for a few minutes and it began smoking accompanied by the terrible smell of electrical components that are overheating. The motor was hot to the touch and the capacitor was leaking some kind of fluid/oil.

I hate to admit defeat, but I am thinking there might be an issue with the motor windings and considering the age of this grinder, I'm considering just cutting my losses and moving on... As I sit here writing this, the stench from the smoke that has permeated my clothing is making me nauseous LOL.

Again, my sincerest thanks and appreciation for the assistance, I am truly grateful.

Joe

 

[brino]

Yeah I think we all know that acrid smell. It always seems to stay in the air for days.
It does sound like a possible bad motor winding......DANG!

I once bought a big heavy grinder for cheap at a yard sale. No way to test the motor, but it was almost free.
Got it back into my shop and yup the motor was dead.
However the shaft was long enough to mount a pulley between the motor and the grinding wheel.
I ran it that way for years with another motor mounted behind it, and then changed to under-bench mount.
Do-able if the original motor bearings are still good and the grinder is good enough to warrant the work.

Brian