Old Drill Press electrical help for DIYer, replacing cord caused short in outlet

adamadamadam01 · Sep 7, 2021

Hello all! So as the title says and as the pictures will demonstrate, I have received a very old drill press. However, the cord was absolutely destroyed and needed to be replaced. I had no experience doing this, but followed along with YT videos and was able to replace all the wires, and added a ground wire as well. However, when I plugged it into my outlet, which I later found out was a GFCI outlet, it caused the outlet to short. My friend and I suspect that the primary reason that this happened was because the surface for the ground wire was not very good, as there was still old paint covering up some of the metal. I was also told that the GFCI outlet could be the issue, but I wanted to make sure that the wiring of the motor looks good before I attempt to plug anything in again. I was told later on told to use a multimeter to test the ground wire, and I was able to get 0 ohms from it, but this was after I filed away all the paint and made sure bare metal was the exposed. I am hoping that those with a better sense for this than me can help me with this diagnosis of what could have gone wrong. I can attach more information and photos as needed, but I am attaching photos of the surface for the ground wire before and after I was able to file away the old paint.

[ElectriciansForums.net] Old Drill Press electrical help for DIYer, replacing cord caused short in outlet

adamadamadam01 · Sep 7, 2021

I will attach a few other pictures of inside the drill press motor as well, in case they help anyone with the diagnosis of possible problems.

littlespark · Sep 8, 2021

It looks likely the lid is touching the exposed copper on the black cable, but if the flex was deteriorated, then I’d expect some of the internal wiring to be not so good either.

It may not have worked for some time.

telectrix · Sep 8, 2021

as he says^^^. also those crimps look like they've been squashed with a hammer. there's bare copper exposed.get them redone with a decent crimping tool and make sure nothing can short out.

Lucien Nunes · Sep 8, 2021

when I plugged it into my outlet, which I later found out was a GFCI outlet, it caused the outlet to short.

Presumably you mean it caused the GFCI to trip? This could be due either to a short-circuit (e.g. where your hot or neutral wires are touching the grounded case of the motor) or a fault within the windings. With the power disconnected, use the 20MΩ range on the multimeter to measure between hot and ground, and neutral and ground. You are looking for a high reading. If it is low e.g. 0.01, click the range on the multimeter down to get the best reading you can as this can indicate what sort of problem exists.

As above the ring terminals are not properly attached - they need to be fitted using the correct tool with the insulation inside the plastic sleeve. But that in itself is not causing your GFCI trip unless the bare copper is touching the motor case.

adamadamadam01 · Sep 8, 2021

Thank you all for the help! I will try these things and report back. Also, here is a picture of the original wiring, I matched up the new black and white wires to the same spots as they were in this original picture. Hopefully that's what I was supposed to do.

adamadamadam01 · Sep 8, 2021

Edit: I was told by someone else that I might have the black and white cables in the opposite spots, and to use a multimeter to test this. However, I don't know what I need to do in order to determine if they are indeed in the correct spot

Lucien Nunes · Sep 8, 2021

The black hot wire should go to the switch. Swapping black and white would not trip the GFCI, it would still.work, only the motor would be live with tbe switch off.

Do the test I mentioned, from hot and neutral to the motor housing.

adamadamadam01 · Sep 8, 2021

Lucien Nunes said:
The black hot wire should go to the switch. Swapping black and white would not trip the GFCI, it would still.work, only the motor would be live with tbe switch off.

Do the test I mentioned, from hot and neutral to the motor housing.

Thank you. For the test, 2 quick questions. 1. Can I do it by putting the red wire metal lead from the multimeter on the prongs of the cord (1 at a time obviously and then then the black wire lead on the metal body)? Or do I put the red wire lead from the multimeter on the screw/nut where the wire is connected, or does it not make a difference which of the two I put the red lead on? 2. If I get a reading of OL while doing this would that be acceptable for what i'm looking for?

Lucien Nunes · Sep 8, 2021

No difference where you put the meter probe (prong or terminal screw) but make sure the switch is on. Yes you are looking for an OL indication on the highest resistance range if possible. This does not 100% guarantee that the windings are OK but it's a good start.

adamadamadam01 · Sep 8, 2021

Lucien Nunes said:
No difference where you put the meter probe (prong or terminal screw) but make sure the switch is on. Yes you are looking for an OL indication on the highest resistance range if possible. This does not 100% guarantee that the windings are OK but it's a good start.

Ok, in regards to making sure the switch is on, that also brings me to another question, because the drill press' power switch doesn't state which way is off and which is on. So is there also a test I can run to determine how I know when the switch is off and when it is on, without plugging it into the wall obviously

Lucien Nunes · Sep 8, 2021

Set the meter to continuity buzzer or 200 ohms range. Put the meter probes onto the screw terminals of tbe switch. Ensure the plug prongs dom't touch anything. Meter will buzz or should dispay low reading <1Ω when on.

adamadamadam01 · Sep 8, 2021

Lucien Nunes said:
Set the meter to continuity buzzer or 200 ohms range. Put the meter probes onto the screw terminals of tbe switch. Ensure the plug prongs dom't touch anything. Meter will buzz or should dispay low reading <1Ω when on.

Thank you, I just did this and found out which way the switch should be for the machine to be off/on. So I did have one more part that I'm going to work on in you have any input.
This red wire is a part of the motor and I either want to either replace it by cutting off the end and soldering it to a new 10g wire, or by putting some heat shrink wrap over the end of the wire. Do you think the heat shrink wrap would be good enough in this case or should I redo the wire?

View attachment 89809

There's also these other wires that have exposed wires, but I'm not exactly sure what is holding them in place. Idk it just solder or what? These wires are on the back side of where the red wire is attached.

Lucien Nunes · Sep 9, 2021

The test from hot and neutral to ground was OK then?

Heatshrink those red and black flyleads right up to the ring of the terminal. Don't bend them any more than needed and don't untie the binding where they are attached to the stator.

The wires on the back of that paxolin strip are soldered to the screws. I expect those are the feed to the start winding, one of which goes via the centrifugal switch. The red and black with the ring terminals are the feed to the run winding. The direction of the motor is set by swapping red and black to the opposite screws, which reverses the relative phase of the start and run winding.

adamadamadam01 · Sep 10, 2021

Lucien Nunes said:
The test from hot and neutral to ground was OK then?

So I did tests with touching one prong of the multimeter to the right and left prong of the cord, and touching the other prong of the multimeter to a screw inside the motor that holds the wires in place. I also touched the two prongs of the multimeter to the two prongs of the cord at the same time. In all 3 tests, the multimeter made a beep tone when I set it at 200 Ohms resistance.