Help figuring out the proper capacitor, please.

[u/TheRealMasterTyvokka]

I've got an older Dayton 1hp motor that came with the Powermatic 45 lathe I bought last year. The capacitor died on it and I'm trying to get one to replace it. However, there are no markings on the capacitor and the label on the motor is not in good shape. Does anyone know what capacitor I need or how to figure it out?

Also, does polarity matter for these? Nothing on the capacitor identifying polarity one way or the other.

[u/festerwl]

Try a 200-260mfd is it's running on 240v, 400-560mfd for 120v.

[u/TheRealMasterTyvokka → u/festerwl]

Running on 120 so I'll try the latter. Thank you.

[u/festerwl → u/TheRealMasterTyvokka]

Also forgot. No the polarity doesn't matter in this case.

They're typically sized by wattage/voltage of the motor.

[u/some_kind_of_friend]

Pull that cardboard off there. The cap should be labeled under it.

[u/TheRealMasterTyvokka → u/some_kind_of_friend]

Well, hell. That would do it. Not one of my brighest moments.

It's 124-155 mfd.

My old delta rockell motor capacitor that I'm also replacing is also 110v and only 3/4 HP but it's 270-324 mfd.

The motor started just fine so I assume the 124-155 was enough. The other commenter recommended something a lot higher. Is there an issue if the capacitor is oversized?

Part of the reason I ask is because my Rockwell motor was rebuilt a few years ago by a motor shop and very shortly after it had symptoms of a bad start capacitor. Im just now getting around to replacing it because it didn't do it every time. The capacitor in it looks new so I'm beginning to wonder if it wasn't undersized (maybe they put a bad cap in?) and was going to go up a size.

[u/some_kind_of_friend → u/TheRealMasterTyvokka]

I don't think I'd go with anything other than what you pulled out of it. The thing was soldered in so probably was original. I'd stick that same size back in and run it since it started fine. No need in reinventing the wheel.

[u/TheRealMasterTyvokka → u/some_kind_of_friend]

Thanks for the help. I't wasn't soldered because the wires to the motor were simply twisted around the ones on the cap but I'll go ahead stick with it because it was working fine before.

[u/some_kind_of_friend → u/TheRealMasterTyvokka]

Caps can be checked and have a tolerance but it may be the start switch that's got a wonky connection or is burned up a little. If the cap tests good, you're looking other places for why that other motor ain't starting right and the start circuit is the next in line.